View source for Large Hadron Collider

{{Short description|Particle accelerator at CERN, Switzerland}}
{{Redirect|LHC}}
{{Use dmy dates|date=December 2015}}
{{Use Oxford spelling|date=August 2016}}
{{Infobox particle accelerator
| name           = Large Hadron Collider (LHC)
| image          = LHC.svg
| caption        = Layout of the LHC complex
| type           = [[Synchrotron]]
| beam           = [[proton]], heavy ion
| target         = [[collider]]
| energy         = 6.8 TeV per beam (13.6 TeV collision energy)
| current        = 
| luminosity     = {{val|1e34|up=cm<sup>2</sup>⋅s}}
| circumference  = {{convert|26659|m|mi|disp=br()}}
| location       = Near [[Geneva]], [[Switzerland]]; across the border of [[France]] and Switzerland.
| coordinates    = {{Coord|46|14|06|N|06|02|42|E|type:landmark|display=inline}}
| institution    = [[CERN]]
| dates          = {{start date and age|2010}} – present
| preceded       = [[Large Electron–Positron Collider]]
}}
{{LHC}}
{{CERNaccelerators}}

The '''Large Hadron Collider''' ('''LHC''')  is the world's largest and highest-energy [[particle accelerator]].<ref name="TheLHC">{{cite web |url=https://home.cern/topics/large-hadron-collider |title=The Large Hadron Collider |date=28 June 2023 |publisher=CERN}}</ref><ref name="Harman">{{cite journal|author=Joel Achenbach|date=March 2012|title=The God Particle|url=http://ngm.nationalgeographic.com/2008/03/god-particle/achenbach-text|archive-url=https://web.archive.org/web/20080225104327/http://ngm.nationalgeographic.com/2008/03/god-particle/achenbach-text|url-status=dead|archive-date=25 February 2008|journal=[[National Geographic Magazine]]|access-date=25 February 2008}}</ref> It was built by the [[CERN|European Organization for Nuclear Research]] (CERN) between 1998 and 2008, in collaboration with over 10,000 scientists, and hundreds of universities and laboratories across more than 100 countries.<ref>{{cite news |first=Roger |last=Highfield |date=16 September 2008 |title=Large Hadron Collider: Thirteen ways to change the world |url=https://www.telegraph.co.uk/science/large-hadron-collider/3351899/Large-Hadron-Collider-thirteen-ways-to-change-the-world.html |archive-url=https://web.archive.org/web/20090924011335/http://www.telegraph.co.uk/science/large-hadron-collider/3351899/Large-Hadron-Collider-thirteen-ways-to-change-the-world.html |url-status=dead |archive-date=24 September 2009 |work=[[The Daily Telegraph]] |access-date=10 October 2008 |location=London}}</ref> It lies in a tunnel {{convert|27|km|mi}} in circumference and as deep as {{convert|175|m|ft}} beneath the [[France–Switzerland border]] near [[Geneva]].

The first collisions were achieved in 2010 at an energy of 3.5&nbsp;[[tera-]][[electronvolt]]s (TeV) per beam, about four times the previous world record.<ref name=bbc20100330>{{cite news |work=BBC News |date=30 March 2010 |title=CERN LHC sees high-energy success |url=http://news.bbc.co.uk/2/hi/science/nature/8593780.stm|access-date=30 March 2010}}</ref><ref name="CERN Press 1">{{cite press release |url=http://press.cern/press-releases/2012/02/lhc-run-4-tev-beam-2012 |title=LHC to run at 4&nbsp;TeV per beam in 2012 |date=13 February 2012 |website=Media and Press Relations |publisher=CERN}}</ref> The discovery of the [[Higgs boson]] at the LHC was announced in 2012. Between 2013 and 2015, the LHC was shut down and upgraded; after those upgrades it reached 6.5&nbsp;TeV per beam (13.0&nbsp;TeV total collision energy).<ref name="BBC" /><ref>{{cite web |last1=O'Luanaigh|first1=Cian|title=Proton beams are back in the LHC|url=http://home.web.cern.ch/about/updates/2015/04/proton-beams-are-back-lhc |publisher=CERN |access-date=24 April 2015}}</ref><ref name="2015restart">{{cite news |url=https://www.bbc.co.uk/news/science-environment-32976838|title=Large Hadron Collider turns on 'data tap'|access-date=28 August 2015|date=3 June 2015|last1=Rincon|first1=Paul}}</ref><ref>{{cite news |url=https://www.bbc.co.uk/news/science-environment-32809636 |title=LHC smashes energy record with test collisions|access-date=28 August 2015|date=21 May 2015|last1=Webb|first1=Jonathan}}</ref> At the end of 2018, it was shut down for maintenance and further upgrades, and reopened over three years later in April 2022.<ref>{{Cite web |date=2023-10-07 |title=2022 Digital Media Kit: Higgs10, LHC Run 3 and restart |url=https://home.cern/press/2022 |access-date=2023-10-10 |website=CERN |language=en}}</ref>

The collider has four crossing points where the accelerated particles collide. [[#Detectors|Nine detectors]],<ref name="FactsFiguresAnoutLHC">{{cite web |title=Facts and figures about the LHC |url=https://home.cern/resources/faqs/facts-and-figures-about-lhc |publisher=CERN |access-date=17 April 2023}}</ref> each designed to detect different phenomena, are positioned around the crossing points. The LHC primarily collides proton beams, but it can also accelerate beams of heavy [[ions]], such as in [[lead]]–lead collisions and [[proton]]–lead collisions.<ref>{{Cite web |date=2023-10-07 |title=Time for lead collisions in the LHC |url=https://home.cern/news/news/accelerators/time-lead-collisions-lhc |access-date=2023-10-10 |website=CERN |language=en}}</ref>

The LHC's goal is to allow physicists to test the predictions of different theories of [[particle physics]], including measuring the properties of the [[Higgs boson]],<ref>{{cite web|year=2008|title=Missing Higgs |url=http://public.web.cern.ch/public/en/Science/Higgs-en.html |publisher=CERN |access-date=10 October 2008}}</ref> searching for the large family of new particles predicted by [[supersymmetry|supersymmetric theories]],<ref>{{cite web|year=2008|title=Towards a superforce |url=http://public.web.cern.ch/public/en/Science/Superforce-en.html |publisher=CERN |access-date=10 October 2008}}</ref> and studying other [[List of unsolved problems in physics#High-energy physics/particle physics|unresolved questions in particle physics]].

== Background ==
The term ''[[hadron]]'' refers to [[Subatomic particle|subatomic]] [[composite particle]]s composed of [[quark]]s [[bound state|held together]] by the [[strong force]] (analogous to the way that [[atom]]s and [[molecule]]s are held together by the [[electromagnetic force]]).<ref>{{cite web|url=http://lhcb-public.web.cern.ch/lhcb-public/en/Physics/Antimatter-en.html|title=LHCb – Large Hadron Collider beauty experiment|website=lhcb-public.web.cern.ch}}</ref> The best-known hadrons are the [[baryon]]s such as protons and [[neutron]]s; hadrons also include [[meson]]s such as the [[pion]] and [[kaon]], which were discovered during [[cosmic ray]] experiments in the late 1940s and early 1950s.<ref>{{cite journal|doi=10.1103/PhysRev.52.1003|title=New Evidence for the Existence of a Particle of Mass Intermediate Between the Proton and Electron|journal=Physical Review|volume=52|issue=9|page=1003|year=1937|last1=Street|first1=J.|last2=Stevenson|first2=E.|bibcode=1937PhRv...52.1003S|s2cid=1378839 |issn = 0031-899X}}</ref>

A ''[[collider]]'' is a type of a [[particle accelerator]] that brings two opposing [[particle]] beams together such that the particles collide. In [[particle physics]], colliders, though harder to construct, are a powerful research tool because they reach a much higher [[center of mass]] energy than [[Fixed-target experiment|fixed target]] setups.<ref name=TheLHC/> Analysis of the byproducts of these collisions gives scientists good evidence of the structure of the [[subatomic]] world and the laws of nature governing it. Many of these byproducts are produced only by high-energy collisions, and they decay after very short periods of time. Thus many of them are hard or nearly impossible to study in other ways.<ref>{{cite web|url=https://atlas.cern/discover/physics|title=The Physics|date=26 March 2015|website=ATLAS Experiment at CERN}}</ref>

== Purpose ==
Many [[physicist]]s hope that the Large Hadron Collider will help answer some of the [[unanswered questions in physics|fundamental open questions]] in physics, which concern the basic laws governing the interactions and forces among [[elementary particle]]s and the deep structure of space and time, particularly the interrelation between [[quantum mechanics]] and [[general relativity]].<ref>{{Cite news|url=https://www.nytimes.com/2007/05/15/science/15cern.html|title=CERN – Large Hadron Collider – Particle Physics – A Giant Takes On Physics' Biggest Questions|last=Overbye|first=Dennis|date=15 May 2007|work=The New York Times|access-date=23 October 2019|language=en-US|issn=0362-4331}}</ref>

These [[high-energy particle]] experiments can provide data to support different scientific models. For example, the [[Standard Model]] and [[Higgsless model]] required high-energy particle experiment data to validate their predictions and allow further theoretical development. The Standard Model was completed by detection of the Higgs boson by the LHC in 2012.<ref>{{Cite web |title=The Standard Model |url=https://www.iop.org/explore-physics/big-ideas-physics/standard-model#gref |access-date=10 October 2023 |website=The Institute of Physics}}</ref>

LHC collisions have explored other questions, including:<ref>{{cite book |last1=Giudice |first1=G. F. |year=2010 |title=A Zeptospace Odyssey: A Journey Into the Physics of the LHC |url=http://giudice.web.cern.ch/giudice/zeptospace/zepto-eng.html |publisher=[[Oxford University Press]] |isbn=978-0-19-958191-7 |access-date=11 August 2013 |archive-url=https://web.archive.org/web/20131101054656/http://giudice.web.cern.ch/giudice/zeptospace/zepto-eng.html |archive-date=1 November 2013 |url-status=dead }}</ref><ref>{{cite news |author=Brian Greene |date=11 September 2008 |title=The Origins of the Universe: A Crash Course |url=https://www.nytimes.com/2008/09/12/opinion/12greene.html?_r=1&oref=slogin |work=[[The New York Times]] |access-date=17 April 2009}}</ref>
* Do all known particles have [[Superpartner|supersymmetric partners]], as part of [[supersymmetry]] in an [[Beyond the Standard Model|extension of the Standard Model]] and [[Super-Poincaré algebra|Poincaré symmetry]]?<ref>{{cite journal |author=[[Shaaban Khalil]] |year=2003 |title=Search for supersymmetry at LHC |journal=[[Contemporary Physics]] |volume=44 |issue=3 |pages=193–201 |bibcode=2003ConPh..44..193K |doi=10.1080/0010751031000077378|s2cid=121063627 }}</ref><ref>{{cite journal |author=Alexander Belyaev |year=2009 |title=Supersymmetry status and phenomenology at the Large Hadron Collider |journal=[[Pramana (journal)|Pramana]] |volume=72 |issue=1 |pages=143–160 |bibcode=2009Prama..72..143B |doi=10.1007/s12043-009-0012-0|s2cid=122457391 }}</ref><ref>{{cite web |author=Anil Ananthaswamy |date=11 November 2009 |title=In SUSY we trust: What the LHC is really looking for |url=https://www.newscientist.com/article/mg20427341.200-in-susy-we-trust-what-the-lhc-is-really-looking-for.html |website=[[New Scientist]]}}</ref>
* Are there [[Superstring theory|extra dimensions]],<ref>{{cite journal |author=Lisa Randall |year=2002 |title=Extra Dimensions and Warped Geometries |url=http://randall.physics.harvard.edu/RandallCV/Sciencearticle.pdf |journal=[[Science (journal)|Science]] |volume=296 |issue=5572 |pages=1422–1427 |doi=10.1126/science.1072567 |pmid=12029124 |bibcode=2002Sci...296.1422R |s2cid=13882282 |access-date=3 September 2008 |archive-date=7 October 2018 |archive-url=https://web.archive.org/web/20181007125941/http://randall.physics.harvard.edu/RandallCV/Sciencearticle.pdf |url-status=dead }}</ref> as predicted by various models based on [[string theory]], and can we detect them?<ref>{{Cite book |author=Panagiota Kanti |year=2009 |title=Physics of Black Holes |volume=769 |pages=387–423 |arxiv=0802.2218 |bibcode=2009LNP...769..387K |doi=10.1007/978-3-540-88460-6_10 |isbn=978-3-540-88459-0 |series=[[Lecture Notes in Physics]]|chapter=Black Holes at the Large Hadron Collider |s2cid=17651318 }}</ref>
* What is the nature of the [[dark matter]], a hypothetical form of matter which appears to account for 27% of the mass-energy of the [[universe]]?

Other open questions that may be explored using high-energy particle collisions include:
* It is already known that [[electromagnetism]] and the [[weak nuclear force]] are different manifestations of a single force called the electroweak force. The LHC may clarify whether the electroweak force and the [[strong nuclear force]] are similarly just different manifestations of one universal unified force, as predicted by various [[Grand unification theory|Grand Unification Theories]].
* Why is the fourth fundamental force ([[Gravitation|gravity]]) so many orders of magnitude weaker than the other three [[fundamental interaction|fundamental forces]]? See also [[Hierarchy problem#The Higgs mass|Hierarchy problem]].
* Are there additional sources of [[quark]] [[flavour (particle physics)|flavour]] mixing beyond those already present within the [[Standard Model]]?
* Why are there apparent violations of the [[symmetry in physics|symmetry]] between matter and [[antimatter]]? See also [[CP violation]].
* What are the nature and properties of [[quark–gluon plasma]], thought to have existed in the [[early universe]] and in certain [[compact star|compact]] and [[strange matter|strange]] astronomical objects today? This will be investigated by ''heavy ion collisions'', mainly in [[A Large Ion Collider Experiment|ALICE]], but also in [[Compact Muon Solenoid|CMS]], [[ATLAS experiment|ATLAS]] and [[LHCb]]. First observed in 2010, findings published in 2012 confirmed the phenomenon of [[jet quenching]] in heavy-ion collisions.<ref>{{cite web |url=http://home.web.cern.ch/about/physics/heavy-ions-and-quark-gluon-plasma |title=Heavy ions and quark–gluon plasma |publisher=CERN|date=18 July 2012}}</ref><ref>{{cite press release |title=LHC experiments bring new insight into primordial universe |url=http://press.cern/press-releases/2010/11/lhc-experiments-bring-new-insight-primordial-universe |website=Media and Press Relations |publisher=CERN |date=26 November 2010 |access-date=2 December 2010}}</ref><ref>{{cite journal |last1=Aad |first1=G. |display-authors=etal |collaboration=ATLAS Collaboration |title=Observation of a Centrality-Dependent Dijet Asymmetry in Lead–Lead Collisions at {{sqrt|''s''<sub>NN</sub>}} = 2.76&nbsp;TeV with the ATLAS detector at the LHC |journal=Physical Review Letters |year=2010 |volume=105 |issue=25 |pages=252303 |doi=10.1103/PhysRevLett.105.252303 |doi-access=free |pmid=21231581 |bibcode=2010PhRvL.105y2303A |arxiv=1011.6182}}</ref>

== Design ==
The collider is contained in a circular tunnel, with a circumference of {{convert|26.7|km|mi}}, at a depth ranging from {{convert|50|to|175|m}} underground. The variation in depth was deliberate, to reduce the amount of tunnel that lies under the [[Jura Mountains]] to avoid having to excavate a vertical access shaft there. A tunnel was chosen to avoid having to purchase expensive land on the surface and to take advantage of the shielding against background radiation that the [[Earth's crust]] provides.<ref>{{cite web |url=https://cds.cern.ch/record/2255762/files/CERN-Brochure-2017-002-Eng.pdf |title=LHC The Guide FAQ |website=cds.cern.ch |date=February 2017 |access-date=23 July 2021 }}</ref>

[[File:Location Large Hadron Collider.PNG|thumb|left|Map of the Large Hadron Collider at CERN]]
The {{convert|3.8|m|adj=on}} wide concrete-lined tunnel, constructed between 1983 and 1988, was formerly used to house the [[Large Electron–Positron Collider]].<ref>{{cite web |year=2008 |title=The Z factory |url=http://public.web.cern.ch/PUBLIC/en/Research/LEP-en.html |publisher=CERN |access-date=17 April 2009}}</ref> The tunnel crosses the border between Switzerland and France at four points, with most of it in France. Surface buildings hold ancillary equipment such as compressors, ventilation equipment, control electronics and refrigeration plants.
[[File:LHC quadrupole magnets.jpg|thumb|Superconducting [[quadrupole magnet|quadrupole electromagnets]] are used to direct the beams to four intersection points, where interactions between accelerated protons take place.]]
The collider tunnel contains two adjacent parallel [[beamline]]s (or ''beam pipes'') each containing a beam, which travel in opposite directions around the ring. The beams intersect at four points around the ring, which is where the particle collisions take place. Some 1,232 [[dipole magnet]]s keep the beams on their circular path (see image<ref>{{cite book | editor1-first=E. M. | editor1-last=Henley | editor2-first=S. D. | editor2-last=Ellis | title=100 Years of Subatomic Physics | publisher=World Scientific | year=2013 | isbn=978-981-4425-80-3 | doi=10.1142/8605 }}</ref>), while an additional 392 [[quadrupole magnet]]s are used to keep the beams focused, with stronger quadrupole magnets close to the intersection points in order to maximize the chances of interaction where the two beams cross. Magnets of [[Multipole expansion|higher multipole orders]] are used to correct smaller imperfections in the field geometry. In total, about 10,000 [[superconducting magnet]]s are installed, with the dipole magnets having a mass of over 27 tonnes.<ref name="LHC 2008-20013">{{cite journal|author= Stephen Myers |title=The Large Hadron Collider 2008–2013|date=4 October 2013|journal=[[International Journal of Modern Physics A]]|volume=28|issue=25|pages=1330035-1–1330035-65 |doi=10.1142/S0217751X13300354  |doi-access=free  |bibcode = 2013IJMPA..2830035M  |bibcode-access=free}}</ref> About 96 tonnes of [[superfluid helium-4]] is needed to keep the magnets, made of copper-clad [[niobium-titanium]], at their [[operating temperature]] of {{convert|1.9|K|C}}, making the LHC the largest [[cryogenics|cryogenic]] facility in the world at liquid helium temperature. LHC uses 470 tonnes of Nb–Ti superconductor.<ref>{{Cite web|url=https://www.researchgate.net/publication/224055541|title=Status of the LHC superconducting cable mass production}}</ref>

During LHC operations, the CERN site draws roughly 200&nbsp;[[Megawatt|MW]] of electrical power from the French [[electrical grid]], which, for comparison, is about one-third the energy consumption of the city of Geneva; the LHC accelerator and detectors draw about 120 MW thereof.<ref>{{cite web |url=https://home.cern/about/engineering/powering-cern |title=Powering CERN |publisher=CERN |year=2018 |access-date=23 June 2018}}</ref> Each day of its operation generates 140 [[terabyte]]s of data.<ref>{{Cite journal|last=Brady|first=Henry E.|date=2019-05-11|title=The Challenge of Big Data and Data Science|journal=Annual Review of Political Science|language=en|volume=22|issue=1|pages=297–323|doi=10.1146/annurev-polisci-090216-023229| doi-access=free|issn=1094-2939}}</ref>

When running an energy of 6.5&nbsp;TeV per proton,<ref>{{cite web |title=First successful beam at record energy of 6.5 TeV |url=http://home.cern/about/updates/2015/04/first-successful-beam-record-energy-65-tev |date=10 April 2015 |access-date=10 January 2016}}</ref> once or twice a day, as the protons are accelerated from 450&nbsp;[[electron volt|GeV]] to 6.5&nbsp;[[electron volt|TeV]], the field of the superconducting dipole magnets is increased from 0.54 to {{nowrap|7.7 [[Tesla (unit)|teslas (T)]]}}. The protons each have an [[energy]] of 6.5&nbsp;TeV, giving a total collision energy of 13&nbsp;TeV. At this energy, the protons have a [[Lorentz factor]] of about 6,930 and move at about {{gaps|0.999|999|990|u=''c''}}, or about {{convert|3.1|m/s|km/h|0|abbr=on}} slower than the [[speed of light]] (''c''). It takes less than {{nowrap|90 [[microsecond]]s (μs)}} for a proton to travel 26.7&nbsp;km around the main ring. This results in {{nowrap|11,245 revolutions}} per second for protons whether the particles are at low or high energy in the main ring, since the speed difference between these energies is beyond the fifth decimal.<ref>{{cite web |title=Acoustic measurements at LHC collimators |first1=D.|last1=Deboy |first2=R.W.|last2=Assmann |first3=F.|last3=Burkart |first4=M.|last4=Cauchi |first5=D.|last5=Wollmann |date=29 August 2011 |website=LHC Collimation Project |url=https://indico.cern.ch/event/138175/contributions/143308/attachments/115687/164260/2011_08_WGMeeting_ddeboy.pdf |quote=The ring operates with an acoustic fundamental and overtones of 11.245 kHz}}</ref>

Rather than having continuous beams, the protons are bunched together, into up to {{nowrap|2,808 bunches}}, with {{nowrap|115 billion protons}} in each bunch so that interactions between the two beams take place at discrete intervals, mainly {{nowrap|25 [[nanosecond]]s (ns)}} apart, providing a bunch collision rate of 40&nbsp;MHz. It was operated with fewer bunches in the first years. The design [[Luminosity (scattering theory)|luminosity]] of the LHC is 10<sup>34</sup> cm<sup>−2</sup>s<sup>−1</sup>,<ref>{{cite web|url=http://cdsweb.cern.ch/record/1228285/files/ATL-DAQ-PROC-2009-044.pdf|title=Operational Experience of the ATLAS High Level Trigger with Single-Beam and Cosmic Rays|access-date=29 October 2010}}</ref> which was first reached in June 2016.<ref name="designlumireached">{{cite web|url=https://home.cern/about/updates/2016/07/lhc-performance-reaches-new-highs|title=LHC performance reaches new highs|date=13 July 2016|access-date=13 May 2017}}</ref> By 2017, twice this value was achieved.<ref name="endof2017" />

[[File:CERN LHC Proton Source.JPG|thumb|left|The LHC protons originate from the small red hydrogen tank.]]
Before being injected into the main accelerator, the particles are prepared by a series of systems that successively increase their energy. The first system is the [[linear particle accelerator]] [[Linac4]] generating 160&nbsp;MeV negative hydrogen ions (H<sup>−</sup> ions), which feeds the [[Proton Synchrotron Booster]] (PSB). There, both electrons are stripped from the hydrogen ions leaving only the nucleus containing one proton. Protons are then accelerated to 2&nbsp;GeV and injected into the [[Proton Synchrotron]] (PS), where they are accelerated to 26&nbsp;GeV. Finally, the [[Super Proton Synchrotron]] (SPS) is used to increase their energy further to 450&nbsp;GeV before they are at last injected (over a period of several minutes) into the main ring. Here, the proton bunches are accumulated, accelerated (over a period of {{nowrap|20 minutes}}) to their peak energy, and finally circulated for 5 to {{nowrap|24 hours}} while collisions occur at the four intersection points.<ref name="irfu1">{{cite web|author=Jörg Wenninger|date=November 2007|title=Operational challenges of the LHC|url=http://irfu.cea.fr/Phocea/file.php?class=std&file=Seminaires/1595/Dapnia-Nov07-partB.ppt|format=PowerPoint|page=53|access-date=17 April 2009}}</ref>

The LHC physics programme is mainly based on proton–proton collisions. However, during shorter running periods, typically one month per year, heavy-ion collisions are included in the programme. While lighter ions are considered as well, the baseline scheme deals with [[lead]] ions<ref>{{cite web|date=1 November 2007|title=Ions for LHC (I-LHC) Project|url=http://project-i-lhc.web.cern.ch/project-i-lhc/Welcome.htm |publisher=CERN |access-date=17 April 2009}}</ref> (see [[A Large Ion Collider Experiment]]). The lead ions are first accelerated by the linear accelerator [[LINAC 3]], and the [[Low Energy Ion Ring]] (LEIR) is used as an ion storage and cooler unit. The ions are then further accelerated by the PS and SPS before being injected into LHC ring, where they reach an energy of 2.3&nbsp;TeV per [[nucleon]] (or 522&nbsp;TeV per ion),<ref>{{cite web|url=http://home.cern/about/opinion/2015/11/new-energy-frontier-heavy-ions |title=Opinion: A new energy frontier for heavy ions|date=24 November 2015|access-date=10 January 2016}}</ref> higher than the energies reached by the [[Relativistic Heavy Ion Collider]]. The aim of the heavy-ion programme is to investigate [[quark–gluon plasma]], which existed in the [[early universe]].<ref>{{cite web|url=https://www.symmetrymagazine.org/article/revamped-lhc-goes-heavy-metal|title=Revamped LHC goes heavy metal|last=Charley|first=Sarah|website=symmetry magazine|date=25 November 2015 |language=en|access-date=23 October 2019}}</ref>

=== Detectors ===
{{See also|List of Large Hadron Collider experiments}}
Nine detectors have been built in large caverns excavated at the LHC's intersection points. Two of them, the [[ATLAS experiment]] and the [[Compact Muon Solenoid]] (CMS), are large general-purpose [[particle detector]]s.<ref name="Harman" /> [[A Large Ion Collider Experiment|ALICE]] and [[LHCb]] have more specialized roles, while the other five—[[TOTEM]], [[MoEDAL]], [[LHCf]], [[Scattering and Neutrino Detector|SND]] and [[FASER experiment|FASER]]—are much smaller and are for very specialized research. The ATLAS and CMS experiments discovered the Higgs boson, which is strong evidence that the Standard Model has the correct mechanism of giving mass to elementary particles.<ref>{{cite web|url=https://www.smithsonianmag.com/science-nature/how-the-higgs-boson-was-found-4723520/ |title=How the Higgs Boson Was Found|website=Smithsonian Magazine |first1=Brian |last1=Greene |date=July 2013 |language=en|access-date=23 October 2019}}</ref>

[[File:View inside detector at the CMS cavern LHC CERN.jpg|upright|thumb|right|[[Compact Muon Solenoid|CMS]] detector for LHC]]

=== Computing and analysis facilities ===
{{main|Worldwide LHC Computing Grid}}

Data produced by LHC, as well as LHC-related simulation, were estimated at 200 [[petabyte]]s per year.<ref name=wwlhccg/>

The [[LHC Computing Grid]]<ref name="citesciences">{{cite web|url=http://www.cite-sciences.fr/francais/ala_cite/science_actualites/sitesactu/question_actu.php?langue=fr&id_article=16043|title=grille de production : les petits pc du lhc|publisher=Cite-sciences.fr|access-date=22 May 2011}}</ref> was constructed as part of the LHC design, to handle the massive amounts of data expected for its collisions. It is an international collaborative project that consists of a grid-based [[computer network]] infrastructure initially connecting 140 computing centres in 35 countries (over 170 in more than 40 countries {{as of |2012 |lc=y}}). It was designed by [[CERN]] to handle the significant volume of data produced by LHC experiments,<ref name="gridabout">{{cite web |title=About |website= Worldwide LHC Computing Grid |publisher=CERN |url=http://wlcg-public.web.cern.ch/about |access-date=13 May 2017}}</ref> incorporating both private fibre optic cable links and existing high-speed portions of the public [[Internet]] to enable data transfer from CERN to academic institutions around the world. The LHC Computing Grid consists of global federations across Europe, Asia Pacific and the Americas.<ref name=wwlhccg>{{cite web |title=Welcome to the Worldwide LHC Computing Grid |website= Worldwide LHC Computing Grid |publisher=CERN |url=http://wlcg.web.cern.ch/ |access-date=13 May 2017}}</ref>

The [[distributed computing]] project [[LHC@home]] was started to support the construction and calibration of the LHC. The project uses the [[Berkeley Open Infrastructure for Network Computing|BOINC]] platform, enabling anybody with an Internet connection and a computer running [[OS X|Mac OS X]], [[Windows]] or [[Linux]] to use their computer's idle time to simulate how particles will travel in the beam pipes. With this information, the scientists are able to determine how the magnets should be calibrated to gain the most stable "orbit" of the beams in the ring.<ref name="LHC@home">{{cite web|url=http://boinc.berkeley.edu/wiki/LHC@home|title=LHC@home|website=berkeley.edu}}</ref> In August 2011, a second application (Test4Theory) went live which performs simulations against which to compare actual test data, to determine confidence levels of the results.

By 2012, data from over 6 quadrillion ({{val|6|e=15}}) LHC proton–proton collisions had been analysed.<ref name="collisionnumber">{{cite web|url=http://www.slashgear.com/first-lhc-proton-run-ends-in-success-new-milestone-18261452/ |title=First LHC proton run ends in success, new milestone|author=Craig Lloyd|date=18 December 2012|access-date=26 December 2014}}</ref> The LHC Computing Grid had become the world's largest [[computing grid]] in 2012, comprising over 170 computing facilities in a [[distributed computing|worldwide network]] across more than 40 countries.<ref name="msnbc-discovery">{{cite web|url=https://www.nbcnews.com/id/wbna47783507|title=Hunt for Higgs boson hits key decision point |website=NBC News – Science – Technology & Science|date=12 June 2012 }}</ref><ref name="LHGG main page">{{cite web |url=http://wlcg.web.cern.ch/ |title=Welcome to the Worldwide LHC Computing Grid |website= Worldwide LHC Computing Grid |publisher=CERN |quote=[A] global collaboration of more than 170 computing centres in 36 countries … to store, distribute and analyse the ~25 Petabytes (25 million Gigabytes) of data annually generated by the Large Hadron Collider}}</ref><ref name="lhc comp public overview">{{cite web |url=https://wlcg.web.cern.ch/ |title=Welcome to the Worldwide LHC Computing Grid |website= Worldwide LHC Computing Grid |date=23 July 2023 |quote=Currently WLCG is made up of more than 170 computing centers in more than 40 countries … The WLCG is now the world's largest computing grid}}</ref>

== Operational history ==
[[File:Lyn Evans - pictures donated by CERN-1 (cropped).jpg|thumb|upright|[[Lyn Evans]], the project leader of the Large Hadron Collider]]
The LHC first went operational on 10 September 2008,<ref name="CERNPressFirstbeam">{{cite press release |website=Media and Press Relations |publisher=CERN |date=10 September 2008 |title=First beam in the LHC&nbsp;– accelerating science |url=http://press.cern/press-releases/2008/09/first-beam-lhc-accelerating-science |access-date=9 October 2008 |df=dmy }}</ref> but initial testing was delayed for 14 months from 19 September 2008 to 20 November 2009, following a [[magnet quench]] incident that caused extensive damage to over 50 [[superconducting magnet]]s, their mountings, and the [[beamline|vacuum pipe]].<ref name="BBC 2008">{{cite news|author=Paul Rincon|date=23 September 2008 |title=Collider halted until next year|url=http://news.bbc.co.uk/2/hi/science/nature/7632408.stm|publisher=BBC News|access-date=9 October 2008}}</ref><ref name="perdue 2008">{{cite web|url=http://www.physics.purdue.edu/particle/lhc/ |title=Large Hadron Collider – Purdue Particle Physics |publisher=Physics.purdue.edu |access-date=5 July 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120717085441/http://www.physics.purdue.edu/particle/lhc/ |archive-date=17 July 2012 }}</ref><ref name="LHC-is-back">{{cite press release |website=Media and Press Relations |publisher=CERN |date=20 November 2009|title=The LHC is back|url=http://press.cern/press-releases/2009/11/lhc-back |access-date=13 November 2016}}</ref><ref name=CERN20091123>{{cite press release |website=Media and Press Relations |publisher=CERN |date=23 November 2009|title=Two circulating beams bring first collisions in the LHC|url=http://press.cern/press-releases/2009/11/two-circulating-beams-bring-first-collisions-lhc|access-date=13 November 2016}}</ref>

During its first run (2010–2013), the LHC collided two opposing [[Charged particle beam|particle beams]] of either protons at up to 4&nbsp;[[electronvolt|teraelectronvolts]] {{nowrap|(4 TeV}} or {{nowrap|0.64 [[joule|microjoules]])}}, or [[lead]] [[atomic nucleus|nuclei]] (574&nbsp;TeV per nucleus, or 2.76&nbsp;TeV per [[nucleon]]).<ref name="LHCbooklet">{{cite web|date=January 2008 |title=What is LHCb |url=http://cdsmedia.cern.ch/img/CERN-Brochure-2008-001-Eng.pdf |website=CERN FAQ |publisher=CERN Communication Group |page=44 |access-date=2 April 2010 |url-status=dead |archive-url=https://web.archive.org/web/20090326231649/http://cdsmedia.cern.ch/img/CERN-Brochure-2008-001-Eng.pdf |archive-date=26 March 2009 }}</ref><ref>{{cite news|title=Large Hadron Collider rewards scientists watching at Caltech|work=Los Angeles Times|date=31 March 2010|author=Amina Khan|access-date=2 April 2010|url=https://www.latimes.com/archives/la-xpm-2010-mar-31-la-sci-hadron31-2010mar31-story.html}}</ref>  Its first run discoveries included the [[search for the Higgs boson|long-sought]] Higgs boson, several composite particles ([[hadron]]s) like the χ<sub>b</sub> (3P) [[bottomonium]] state, the first creation of a quark–gluon plasma, and the first observations of the very rare decay of the [[Strange B meson|B<sub>s</sub> meson]] into two [[muon]]s (B<sub>s</sub><sup>0</sup> → μ<sup>+</sup>μ<sup>−</sup>), which challenged the validity of existing models of [[supersymmetry]].<ref>
{{cite web |author=M. Hogenboom |date=24 July 2013 |title=Ultra-rare decay confirmed in LHC |url=https://www.bbc.co.uk/news/science-environment-23431797 |publisher=BBC |access-date=18 August 2013}}</ref>

===Construction===

==== Operational challenges ====

The size of the LHC constitutes an exceptional engineering challenge with unique operational issues on account of the amount of energy stored in the magnets and the beams.<ref name="irfu1"/><ref>{{cite web |date=14 January 1999 |title=Challenges in accelerator physics |url=http://lhc.web.cern.ch/lhc/general/acphys.htm |publisher=CERN |access-date=28 September 2009 |archive-url=https://web.archive.org/web/20061005004318/http://lhc.web.cern.ch/lhc/general/acphys.htm |archive-date=5 October 2006 |url-status=dead }}</ref> While operating, the total [[Superconducting magnetic energy storage|energy stored in the magnets]] is {{convert|10|GJ|kgTNT|abbr=on}} and the total energy carried by the two beams reaches {{convert|724|MJ|kgTNT|abbr=on}}.<ref>{{cite book|author=John Poole|year=2004|title=LHC Design Report|chapter=Beam Parameters and Definitions|chapter-url=https://edms.cern.ch/file/445830/5/Vol_1_Chapter_2.pdf}}</ref>

Loss of only one ten-millionth part (10<sup>−7</sup>) of the beam is sufficient to [[Magnet quench|quench]] a superconducting magnet, while each of the two [[beam dump]]s must absorb {{convert|362|MJ|kgTNT|abbr=on}}. These energies are carried by very little matter: under nominal operating conditions (2,808 bunches per beam, 1.15×10<sup>11</sup> protons per bunch), the beam pipes contain 1.0×10<sup>−9</sup> gram of hydrogen, which, in [[standard conditions for temperature and pressure]], would fill the volume of one grain of fine sand.

==== Cost ====
{{see also|List of megaprojects}}

With a budget of €7.5&nbsp;billion (about $9bn or £6.19bn {{as of |2010 |June |lc=y}}), the LHC is one of the most expensive scientific instruments<ref name=TheLHC/> ever built.<ref>{{cite web|author=Agence Science-Presse |url=http://www.lienmultimedia.com/article.php3?id_article=22468 |language=fr |title=LHC: Un (très) petit Big Bang |publisher=Lien Multimedia |date=7 December 2009 |access-date=29 October 2010}} {{Google translation |en|fr|http://www.lienmultimedia.com/article.php3?id_article%3D22468}}</ref> The total cost of the project is expected to be of the order of 4.6bn [[Swiss franc]]s (SFr) (about $4.4bn, €3.1bn, or £2.8bn {{as of |2010|January|lc=y}}) for the accelerator and 1.16bn (SFr) (about $1.1bn, €0.8bn, or £0.7bn {{as of |2010|January|lc=y}}) for the CERN contribution to the experiments.<ref>{{cite web |year=2007 |title=How much does it cost? |url=http://askanexpert.web.cern.ch/AskAnExpert/en/Accelerators/LHCgeneral-en.html#3 |publisher=CERN |access-date=28 September 2009 |url-status=dead |archive-url=https://web.archive.org/web/20110807103920/http://askanexpert.web.cern.ch/AskAnExpert/en/Accelerators/LHCgeneral-en.html#3 |archive-date=7 August 2011 |df=dmy-all}}</ref>

The construction of LHC was approved in 1995 with a budget of SFr 2.6bn, with another SFr 210M toward the experiments. However, cost overruns, estimated in a major review in 2001 at around SFr 480M for the accelerator, and SFr 50M for the experiments, along with a reduction in CERN's budget, pushed the completion date from 2005 to April 2007.<ref>{{cite web|author=Luciano Maiani|date=16 October 2001|title=LHC Cost Review to Completion|url=http://user.web.cern.ch/User/LHCCost/2001-10-16/LHCCostReview.html|publisher=CERN|access-date=15 January 2001|archive-url=https://web.archive.org/web/20081227135127/http://user.web.cern.ch/User/LHCCost/2001-10-16/LHCCostReview.html|archive-date=27 December 2008|url-status=dead}}</ref> The superconducting magnets were responsible for SFr 180M of the cost increase. There were also further costs and delays owing to engineering difficulties encountered while building the cavern for the [[Compact Muon Solenoid]],<ref>{{cite journal|author=Toni Feder|year=2001|title=CERN Grapples with LHC Cost Hike|journal=[[Physics Today]]|volume=54|issue=12|pages=21–22|bibcode=2001PhT....54l..21F|doi=10.1063/1.1445534|doi-access=free}}</ref> and also due to magnet supports which were insufficiently strongly designed and failed their initial testing (2007) and damage from a magnet quench and [[liquid helium]] escape (inaugural testing, 2008).<ref>{{cite web |date=5 April 2007 |url=https://www.reuters.com/article/scienceNews/idUSL054919720070405 |title=Bursting magnets may delay CERN collider project |website=Reuters |access-date=28 September 2009 |url-status=dead |archive-url=https://web.archive.org/web/20070503011021/https://www.reuters.com/article/scienceNews/idUSL054919720070405 |archive-date=3 May 2007}}</ref> Because electricity costs are lower during the summer, the LHC normally does not operate over the winter months,<ref>{{cite news|author=Paul Rincon|date=23 September 2008 |url=http://news.bbc.co.uk/1/hi/sci/tech/7632408.stm |title=Collider halted until next year |work=BBC News |access-date=28 September 2009}}</ref> although exceptions over the 2009/10 and 2012/2013 winters were made to make up for the 2008 start-up delays and to improve precision of measurements of the new particle discovered in 2012, respectively.

==== Construction accidents and delays ====
* On 25 October 2005, José Pereira Lages, a technician, was killed in the LHC when a [[switchgear]] that was being transported fell on top of him.<ref>{{cite press release |author=Robert Aymar |date=26 October 2005 |title=Message from the Director-General |url=https://cds.cern.ch/record/901285?ln=en |website=Media and Press Relations |publisher=CERN |access-date=12 June 2013}}</ref>
* On 27 March 2007, a cryogenic magnet support designed and provided by [[Fermilab]] and [[KEK]] broke during an initial pressure test involving one of the LHC's inner triplet (focusing quadrupole) magnet assemblies. No one was injured. Fermilab director Pier Oddone stated "In this case we are dumbfounded that we missed some very simple balance of forces". The fault had been present in the original design, and remained during four engineering reviews over the following years.<ref>{{cite web |date=4 April 2007 |title=Fermilab 'Dumbfounded' by fiasco that broke magnet |url=https://www.photonics.com/Article.aspx?PID=6&VID=32&IID=230&AID=29203 |publisher=Photonics.com |access-date=28 September 2009}}</ref> Analysis revealed that its design, made as thin as possible for better insulation, was not strong enough to withstand the forces generated during pressure testing. Details are available in a statement from Fermilab, with which CERN is in agreement.<ref>{{cite press release |date=1 June 2007 |title=Fermilab update on inner triplet magnets at LHC: Magnet repairs underway at CERN |url=http://user.web.cern.ch/user/QuickLinks/Announcements/2007/LHCInnerTriplet_5.html |website=Media and Press Relations |publisher=CERN |access-date=28 September 2009 |archive-url=https://web.archive.org/web/20090106233105/http://user.web.cern.ch/user/QuickLinks/Announcements/2007/LHCInnerTriplet_5.html |archive-date=6 January 2009 |url-status=dead }}</ref><ref>{{cite web |date=28 September 2007|title=Updates on LHC inner triplet failure|url=http://www.fnal.gov/pub/today/lhc_magnet_archive.html|website=[[Fermilab Today]]|publisher=[[Fermilab]]|access-date=28 September 2009}}</ref> Repairing the broken magnet and reinforcing the eight identical assemblies used by LHC delayed the start-up date, then planned for November 2007.
* On 19 September 2008, during initial testing, a faulty electrical connection led to a magnet quench (the sudden loss of a superconducting magnet's superconducting ability owing to warming or [[electric field]] effects). Six tonnes of supercooled [[liquid helium]]—used to cool the magnets—escaped, with sufficient force to break 10-ton magnets nearby from their mountings, and caused considerable damage and contamination of the vacuum tube. Repairs and safety checks caused a delay of around 14 months.<ref>{{cite news|author=Paul Rincon|date=23 September 2008|title=Collider halted until next year|url=http://news.bbc.co.uk/2/hi/in_depth/7632408.stm|publisher=BBC News|access-date=29 September 2009}}</ref><ref name="CERNsummer"/><ref>{{cite news|author=Dennis Overbye|date=5 December 2008|title=After repairs, summer start-up planned for collider|url=https://www.nytimes.com/2008/12/06/science/06cern.html|work=[[New York Times]]|access-date=8 December 2008}}</ref>
* Two vacuum leaks were found in July 2009, and the start of operations was further postponed to mid-November 2009.<ref name="July 2009 leaks" />
<!-- NOTE: Please do not add the baguette/breadcrumb story here without discussing on the talk page first. -->

==== Exclusion of Russia ====

With the 2022 [[Russian invasion of Ukraine]], the participation of Russians with CERN was called into question.  About 8% of the workforce are of Russian nationality.  In June 2022, CERN said the governing council "intends to terminate" CERN's cooperation agreements with Belarus and Russia when they expire, respectively in June and December 2024. CERN said it would monitor developments in Ukraine and remains prepared to take additional steps as warranted.<ref>{{cite web|url=https://phys.org/news/2022-06-atom-smashing-cern-terminate-russia-belarus.html |title=Atom-smashing CERN to 'terminate' work with Russia, Belarus |publisher=Phys.org |date= |accessdate=2022-08-01}}</ref><ref>{{cite web|url=https://home.web.cern.ch/news/news/cern/cern-council-cooperation-agreements-russia-belarus |title=CERN Council declares its intention to terminate cooperation agreements with Russia and Belarus at their expiration dates in 2024 &#124; CERN |publisher=Home.web.cern.ch |date=2022-06-17 |accessdate=2022-08-01}}</ref>  CERN further said that it would reduce the Ukrainian contribution to CERN for 2022 to the amount already remitted to the Organization, thereby waiving the second installment of the contribution.<ref>{{cite web|url=https://council.web.cern.ch/en/content/resolutions |title=Resolutions &#124; CERN Council |publisher=Council.web.cern.ch |date= |accessdate=2022-08-12}}</ref>

==== Initial lower magnet currents ====
{{main|Superconducting magnet#Magnet "training"}}

In both of its runs (2010 to 2012 and 2015), the LHC was initially run at energies below its planned operating energy, and ramped up to just 2 x 4&nbsp;TeV energy on its first run and 2 x 6.5&nbsp;TeV on its second run, below the design energy of 2 x 7&nbsp;TeV. This is because massive superconducting magnets require considerable [[Superconducting magnet#Magnet "training"|magnet training]] to handle the high currents involved without [[magnet quench|losing their superconducting ability]], and the high currents are necessary to allow a high proton energy. The "training" process involves repeatedly running the magnets with lower currents to provoke any quenches or minute movements that may result. It also takes time to cool down magnets to their operating temperature of around 1.9 [[Kelvin|K]] (close to [[absolute zero]]). Over time the magnet "beds in" and ceases to quench at these lesser currents and can handle the full design current without quenching; CERN media describe the magnets as "shaking out" the unavoidable tiny manufacturing imperfections in their crystals and positions that had initially impaired their ability to handle their planned currents. The magnets, over time and with training, gradually become able to handle their full planned currents without quenching.<ref name="why13tev">{{cite web |url=http://home.web.cern.ch/about/engineering/restarting-lhc-why-13-tev |title=Restarting the LHC: Why 13 Tev? |publisher=CERN |access-date=28 August 2015}}</ref><ref name="training2">{{cite web |url=http://www.symmetrymagazine.org/article/december-2014/first-lhc-magnets-prepped-for-restart |title=First LHC magnets prepped for restart |website=Symmetry Magazine |date=10 December 2014 |access-date=28 August 2015}}</ref>

=== Inaugural tests (2008) ===

The first beam was circulated through the collider on the morning of 10 September 2008.<ref name=rincon>{{cite news|author=Paul Rincon|date=10 September 2008|url=http://news.bbc.co.uk/1/hi/sci/tech/7604293.stm|title='Big Bang' experiment starts well|publisher=BBC News|access-date=17 April 2009}}</ref> [[CERN]] successfully fired the protons around the tunnel in stages, three kilometres at a time. The particles were fired in a clockwise direction into the accelerator and successfully steered around it at 10:28 local time.<ref name="CERNPressFirstbeam" /> The LHC successfully completed its major test: after a series of trial runs, two white dots flashed on a computer screen showing the protons travelled the full length of the collider. It took less than one hour to guide the stream of particles around its inaugural circuit.<ref>{{cite news|author=Mark Henderson|date=10 September 2008|title=Scientists cheer as protons complete first circuit of Large Hadron Collider|url=http://www.thetimes.co.uk/tto/news/world/article1967054.ece|work=[[Times Online]]|access-date=6 October 2008|location=London}}</ref> CERN next successfully sent a beam of protons in an anticlockwise direction, taking slightly longer at one and a half hours owing to a problem with the [[cryogenics]], with the full circuit being completed at 14:59.

==== Quench incident ====
{{Wikinews|CERN says repairs to LHC particle accelerator to cost US$21&nbsp;million}}

On 19 September 2008, a magnet quench occurred in about 100 bending [[magnet]]s in sectors 3 and 4, where an electrical fault vented about six tonnes of liquid helium (the magnets' [[cryogenic]] coolant) into the tunnel. The escaping vapour expanded with explosive force, damaging 53 superconducting magnets and their mountings, and contaminating the vacuum pipe, which also lost vacuum conditions.<ref name="BBC 2008" /><ref name="perdue 2008" /><ref name="interim technical report">{{cite web|date=15 October 2008|title=Interim Summary Report on the Analysis of the 19 September 2008 Incident at the LHC|url= https://edms.cern.ch/file/973073/1/Report_on_080919_incident_at_LHC__2_.pdf|publisher= CERN |id=EDMS&nbsp;973073|access-date=28 September 2009}}</ref>

Shortly after the incident, CERN reported that the most likely cause of the problem was a [[electrical fault|faulty electrical connection]] between two magnets. It estimated that repairs would take at least two months, owing to the time needed to warm up the affected sectors and then cool them back down to operating temperature.<ref>{{cite press release |date=20 September 2008|title=Incident in LHC sector 3–4|url=http://press.cern/press-releases/2008/09/incident-lhc-sector-3-4 |website=Media and Press Relations |publisher=CERN |access-date=13 November 2016}}</ref> CERN released an interim technical report<ref name="interim technical report" /> and preliminary analysis of the incident on 15 and 16&nbsp;October 2008 respectively,<ref>{{cite press release |date=16 October 2008|title=CERN releases analysis of LHC incident|url=http://press.cern/press-releases/2008/10/cern-releases-analysis-lhc-incident |website=Media and Press Relations |publisher=CERN |access-date=13 November 2016}}</ref> and a more detailed report on 5&nbsp;December 2008.<ref name="CERNsummer">{{cite press release |date=5 December 2008|title=LHC to restart in 2009|url=http://press.cern/press-releases/2008/12/lhc-restart-2009 |website=Media and Press Relations |publisher=CERN |access-date=13 November 2016}}</ref> The analysis of the incident by CERN confirmed that an electrical fault had indeed been the cause. The faulty electrical connection had led (correctly) to a [[failsafe]] power abort of the electrical systems powering the superconducting magnets, but had also caused an [[electric arc]] (or discharge) which damaged the integrity of the supercooled helium's enclosure and vacuum insulation, causing the coolant's temperature and pressure to rapidly rise beyond the ability of the safety systems to contain it,<ref name="interim technical report" /> and leading to a temperature rise of about 100 degrees [[Celsius]] in some of the affected magnets. Energy stored in the superconducting magnets and [[electrical noise]] [[Electromagnetic induction|induced]] in other quench detectors also played a role in the rapid heating. Around two [[tonne]]s of liquid helium escaped explosively before detectors triggered an emergency stop, and a further four tonnes leaked at lower pressure in the aftermath.<ref name="interim technical report" /> A total of 53 magnets were damaged in the incident and were repaired or replaced during the winter shutdown.<ref>{{cite press release |date=30 April 2009 |title=Final LHC magnet goes underground |url=http://press.cern/press-releases/2009/04/final-lhc-magnet-goes-underground |website=Media and Press Relations |publisher=CERN |access-date=13 November 2016}}</ref> This accident was thoroughly discussed in a 22&nbsp;February 2010 ''Superconductor Science and Technology'' article by CERN physicist [[Lucio Rossi]].<ref>{{cite journal|author=L. Rossi|year=2010|title=Superconductivity: its role, its success and its setbacks in the Large Hadron Collider of CERN|journal=[[Superconductor Science and Technology]]|volume=23|issue=3|page=034001|bibcode=2010SuScT..23c4001R|doi=10.1088/0953-2048/23/3/034001|s2cid=53063554 |url=https://cds.cern.ch/record/1235168/files/CERN-ATS-2010-006.pdf}}</ref>

In the original schedule for LHC commissioning, the first "modest" high-energy collisions at a [[center of momentum frame|centre-of-mass]] energy of 900&nbsp;GeV were expected to take place before the end of September 2008, and the LHC was expected to be operating at 10&nbsp;TeV by the end of 2008.<ref>{{cite press release |date=7 August 2008|title=CERN announces start-up date for LHC |url=http://press.cern/press-releases/2008/08/cern-announces-start-date-lhc |website=Media and Press Relations |publisher=CERN |access-date=13 November 2016}}</ref> However, owing to the delay caused by the incident, the collider was not operational until November 2009.<ref name="CERN September">{{cite press release |website=Media and Press Relations |publisher=CERN |date=9 February 2009|title=CERN management confirms new LHC restart schedule|url=http://press.cern/press-releases/2009/02/cern-management-confirms-new-lhc-restart-schedule |access-date=13 November 2016}}</ref> Despite the delay, LHC was officially inaugurated on 21&nbsp;October 2008, in the presence of political leaders, science ministers from CERN's 20 Member States, CERN officials, and members of the worldwide scientific community.<ref>{{cite press release |date=21 October 2008 |title=CERN inaugurates the LHC |url=http://press.cern/press-releases/2008/10/cern-inaugurates-lhc |website=Media and Press Relations |publisher=CERN |access-date=21 October 2008 |df=dmy }}</ref>

Most of 2009 was spent on repairs and reviews from the damage caused by the quench incident, along with two further vacuum leaks identified in July 2009; this pushed the start of operations to November of that year.<ref name="July 2009 leaks">{{cite web |date=16 July 2009 |title=News on the LHC |publisher=CERN |url=http://user.web.cern.ch/user/news/2009/090716.html|access-date=28 September 2009}}</ref>

=== Run 1: first operational run (2009–2013) ===

[[File:Jean Iliopoulos (Ecole Normale Supérieure) - Philippe Binant Archives.jpg|thumb|Seminar on the [[physics]] of LHC by [[John Iliopoulos]] (2009)<ref>Seminar on the physics of LHC by John Iliopoulos, [[École Normale Supérieure]], Paris, 2009.</ref>]]

On 20 November 2009, low-energy beams circulated in the tunnel for the first time since the incident, and shortly after, on 30 November, the LHC achieved 1.18&nbsp;TeV per beam to become the world's highest-energy particle accelerator, beating the [[Tevatron]]'s previous record of 0.98&nbsp;TeV per beam held for eight years.<ref name="30 Nov press">{{cite press release |date=30 November 2009|url=http://press.cern/press-releases/2009/11/lhc-sets-new-world-record|title=LHC sets new world record |website=Media and Press Relations |publisher=CERN |access-date=13 November 2016}}</ref>

The early part of 2010 saw the continued ramp-up of beam in energies and early physics experiments towards 3.5&nbsp;TeV per beam and on 30 March 2010, LHC set a new record for high-energy collisions by colliding proton beams at a combined energy level of 7&nbsp;TeV. The attempt was the third that day, after two unsuccessful attempts in which the protons had to be "dumped" from the collider and new beams had to be injected.<ref>{{cite news|url=http://www.thehindu.com/sci-tech/science/article329160.ece|title=Big Bang Machine sets collision record|agency=Associated Press|date=30 March 2010|work=The Hindu}}</ref> This also marked the start of the main research programme.

The first proton run ended on 4 November 2010. A run with lead ions started on 8 November 2010, and ended on 6 December 2010,<ref>{{cite press release |date=8 November 2010 |title=CERN completes transition to lead-ion running at the LHC |url=http://press.cern/press-releases/2010/11/cern-completes-transition-lead-ion-running-lhc |website=Media and Press Relations |publisher=CERN |access-date=28 February 2016 }}</ref> allowing the ALICE experiment to study matter under extreme conditions similar to those shortly after the Big Bang.<ref>{{cite web|url=http://cdsweb.cern.ch/journal/CERNBulletin/2010/45/News%20Articles/1302710?ln=en|title=The Latest from the LHC : Last period of proton running for 2010. – CERN Bulletin|publisher=Cdsweb.cern.ch|date=1 November 2010|access-date=17 August 2011}}</ref>

CERN originally planned that the LHC would run through to the end of 2012, with a short break at the end of 2011 to allow for an increase in beam energy from 3.5 to 4&nbsp;TeV per beam.<ref name="CERN Press 1"/> At the end of 2012, the LHC was planned to be temporarily shut down until around 2015 to allow upgrade to a planned beam energy of 7&nbsp;TeV per beam.<ref>{{cite press release |url=http://press.cern/press-releases/2012/12/first-lhc-protons-run-ends-new-milestone |title=The first LHC protons run ends with new milestone |date=17 December 2012 |website=Media and Press Relations |publisher=CERN}}</ref> In late 2012, in light of the July 2012 discovery of the Higgs boson, the shutdown was postponed for some weeks into early 2013, to allow additional data to be obtained before shutdown.

=== Long Shutdown 1 (2013–2015) ===
[[File:Views of the LHC tunnel sector 3-4, tirage 2.jpg|thumb|A section of the LHC tunnel. The dipole magnets are painted in a blue colour, to protect them from rust.<ref>{{Cite web |title=Why the LHC magnets are blue – and other colourful accelerator questions answered |last=Hortala |first=Thomas |work=CERN |date=19 May 2021 |access-date=20 May 2023 |url= https://home.cern/news/news/accelerators/why-lhc-magnets-are-blue-and-other-colourful-accelerator-questions-answered}}</ref>]]
The LHC was shut down on 13 February 2013 for its two-year upgrade called Long Shutdown 1 (LS1), which was to touch on many aspects of the LHC: enabling collisions at 14&nbsp;TeV, enhancing its detectors and pre-accelerators (the Proton Synchrotron and Super Proton Synchrotron), as well as replacing its ventilation system and {{cvt|100|km}} of cabling impaired by high-energy collisions from its first run.<ref>{{cite web|url=http://home.web.cern.ch/about/updates/2013/02/long-shutdown-1-exciting-times-ahead|title=Long Shutdown 1: Exciting times ahead|website=cern.ch|access-date=28 August 2015}}</ref> The upgraded collider began its long start-up and testing process in June 2014, with the Proton Synchrotron Booster starting on 2 June 2014, the final interconnection between magnets completing and the Proton Synchrotron circulating particles on 18 June 2014, and the first section of the main LHC supermagnet system reaching operating temperature of {{convert|1.9|K|C}}, a few days later.<ref>{{cite web|url=http://home.web.cern.ch/about/updates/2014/06/cern-announces-lhc-restart-schedule|title=CERN|website=cern.ch|access-date=28 August 2015}}</ref> Due to the slow progress with [[Superconducting magnet#Magnet "training"|"training"]] the superconducting magnets, it was decided to start the second run with a lower energy of 6.5&nbsp;TeV per beam, corresponding to a current in the magnet of 11,000 [[ampere]]s. The first of the main LHC magnets were reported to have been successfully trained by 9&nbsp;December 2014, while training the other magnet sectors was finished in March 2015.<ref>{{cite web|url=http://lhc-commissioning.web.cern.ch/lhc-commissioning/news-2015/LHC-latest-news.html|title=LHC 2015 – latest news|website=cern.ch|access-date=19 January 2016}}</ref>

=== Run 2: second operational run (2015–2018) ===

On 5 April 2015, the LHC restarted after a two-year break, during which the electrical connectors between the bending magnets were upgraded to safely handle the current required for 7&nbsp;TeV per beam (14&nbsp;TeV collision energy).<ref name="BBC">{{cite web | url =https://www.bbc.com/news/science-environment-32160755|title=Large Hadron collider restarts after pause|publisher=BBC| author=Jonathan Webb|date=5 April 2015| access-date =5 April 2015}}</ref><ref name="splices">{{cite web | url=https://home.cern/about/updates/2013/03/lhc-consolidations-step-step-guide| title=LHC consolidations: A step-by-step guide| date=10 April 2024|publisher=CERN}}</ref> However, the bending magnets were only [[Superconducting magnet#Magnet "training"|trained]] to handle up to 6.5&nbsp;TeV per beam (13&nbsp;TeV collision energy), which became the operating energy for 2015 to 2018.<ref name="why13tev"/> The energy was first reached on 10 April 2015.<ref>{{cite web |last1=O'Luanaigh|first1=Cian |title=First successful beam at record energy of 6.5 TeV |url=http://home.web.cern.ch/about/updates/2015/04/first-successful-beam-record-energy-65-tev |publisher=CERN |access-date=24 April 2015}}</ref> The upgrades culminated in colliding protons together with a combined energy of 13&nbsp;TeV.<ref name="13TeVcollisions" /> On 3 June 2015, the LHC started delivering physics data after almost two years offline.<ref name=":0">{{cite web |title= Physicists eager for new high-energy Large Hadron Collider run |url= https://www.sciencedaily.com/releases/2015/06/150603181744.htm |website= Science Daily |date=3 June 2015 |access-date= 4 June 2015}}</ref> In the following months, it was used for proton–proton collisions, while in November, the machine switched to collisions of lead ions and in December, the usual winter shutdown started.

In 2016, the machine operators focused on increasing the luminosity for proton–proton collisions. The design value was first reached 29&nbsp;June,<ref name="designlumireached" /> and further improvements increased the collision rate to 40% above the design value.<ref name="2016lumi">{{cite web|url=https://home.cern/cern-people/updates/2016/10/lhc-report-end-2016-proton-proton-operation |title=LHC Report: end of 2016 proton–proton operation|date=31 October 2016|access-date=27 January 2017}}</ref> The total number of collisions in 2016 exceeded the number from Run 1 – at a higher energy per collision. The proton–proton run was followed by four weeks of proton–lead collisions.<ref name="2016summary">{{cite web|url=https://home.cern/cern-people/updates/2016/12/lhc-report-far-beyond-expectations |title=LHC Report: far beyond expectations|date=13 December 2016|access-date=27 January 2017}}</ref>

In 2017, the luminosity was increased further and reached twice the design value. The total number of collisions was higher than in 2016 as well.<ref name="endof2017" />

The 2018 physics run began on 17&nbsp;April and stopped on 3&nbsp;December, including four weeks of lead–lead collisions.<ref>{{Cite web|url=https://beams.web.cern.ch/sites/beams.web.cern.ch/files/schedules/LHC_Schedule_2018.pdf|title=LHC Schedule 2018}}</ref>

===Long Shutdown 2 (2018–2022)===

Long Shutdown 2 (LS2) started on 10 December 2018. The LHC and the whole CERN accelerator complex was maintained and upgraded. The goal of the upgrades was to implement the [[High Luminosity Large Hadron Collider]] (HL-LHC) project that will increase the luminosity by a factor of 10. LS2 ended in April 2022. The Long Shutdown 3 (LS3) in the 2020s will take place before the HL-LHC project is done.

===Run 3: third operational run (2022)===

LHC became operational again on 22 April 2022 with a new maximum beam energy of 6.8&nbsp;TeV (13.6&nbsp;TeV collision energy), which was first achieved on 25&nbsp;April.<ref name="Askanews118">{{cite web|url=https://www.askanews.it/scienza-e-innovazione/2022/04/22/al-cern-riavviato-lhc-il-pi%c3%b9-grande-acceleratore-di-particelle-pn_20220422_00118/|title=Al Cern riavviato LHC, il più grande acceleratore di particelle|language=it|trans-title=LHC, the largest particle accelerator, restarted at CERN|website=[[ASCA (news agency)|Askanews]]|date=22 April 2022|access-date=22 April 2022}}</ref><ref name="CnetRestarts">{{cite news |first=Sean |last=Keane |title=CERN's Large Hadron Collider Restarts After Three-Year Upgrade |url=https://www.cnet.com/science/cerns-large-hadron-collider-restarts-after-three-year-upgrade/ |website=[[CNET]]|date=22 April 2022 |access-date=22 April 2022}}</ref> It officially commenced its run 3 physics season on 5&nbsp;July 2022.<ref>{{cite web |date=2022-06-24 |title= Run 3 physics season announced  |url= https://home.web.cern.ch/news/news/cern/join-cern-historic-week-particle-physics |access-date=2022-06-24 |website=CERN |language=en}}</ref> This round is expected to continue until 2026.<ref>{{cite web |date=2022-04-22 |title=World's biggest particle collider restarts after long break |url=https://www.ctvnews.ca/sci-tech/world-s-biggest-particle-collider-restarts-after-long-break-1.5872039 |access-date=2022-04-22 |website=CERN |language=en}}</ref> In addition to a higher energy the LHC is expected to reach a higher luminosity, which is expected to increase even further with the upgrade to the HL-LHC after Run 3.<ref name="autogenerated1">{{cite web|url=https://home.cern/science/accelerators/new-technologies-high-luminosity-lhc |title=New technologies for the High-Luminosity LHC &#124; CERN |publisher=Home.cern |date= |accessdate=2022-08-01}}</ref>

== Timeline of operations ==
{{update|date=August 2023}}
{{Beyond the Standard Model|expanded=Experiments}}
{|class="wikitable" style="font-size: 0.9em;"
|-
! style="width: 7em;" | Date
! Event
|-
| style="text-align: right; padding-right: 0.9em;" | 10 Sep 2008
|[[CERN]] successfully fired the first protons around the entire tunnel circuit in stages.
|-
| style="text-align: right; padding-right: 0.9em;" | 19 Sep 2008
|[[Magnet quench|Magnetic quench]] occurred in about 100 bending [[magnet]]s in sectors 3 and 4, causing a loss of about 6 tonnes of liquid [[helium]].
|-
| style="text-align: right; padding-right: 0.9em;" | 30 Sep 2008
|First "modest" [[high-energy physics|high-energy]] collisions planned but postponed due to accident.<ref name="LHC 2008-20013"/>
|-
| style="text-align: right; padding-right: 0.9em;" | 16 Oct 2008
|CERN released a preliminary analysis of the accident.
|-
| style="text-align: right; padding-right: 0.9em;" | 21 Oct 2008
|Official inauguration.
|-
| style="text-align: right; padding-right: 0.9em;" | 5 Dec 2008
|CERN released detailed analysis.
|-
| style="text-align: right; padding-right: 0.9em;" | 20 Nov 2009
|Low-energy beams circulated in the tunnel for the first time since the accident.<ref name="LHC-is-back" />
|-
| style="text-align: right; padding-right: 0.9em;" | 23 Nov 2009
|First particle collisions in all four detectors at 450&nbsp;GeV.
|-
| style="text-align: right; padding-right: 0.9em;" | 30 Nov 2009
|LHC becomes the world's highest-energy particle accelerator achieving 1.18&nbsp;TeV per beam, beating the [[Tevatron]]'s previous record of 0.98&nbsp;TeV per beam held for eight years.<ref name="30 nov press">{{cite press release |date=30 November 2009|url=http://press.cern/press-releases/2009/11/lhc-sets-new-world-record|title=LHC sets new world record |website=Media and Press Relations |publisher=CERN |access-date=2016-11-13}}</ref>
|-
| style="text-align: right; padding-right: 0.9em;" | 15 Dec 2009
|First scientific results, covering 284 collisions in the ALICE detector.<ref name="first science 2009">[http://news.softpedia.com/news/First-Science-Produced-at-LHC-129833.shtml First Science Produced at LHC] 2009-12-15</ref>
|-
| style="text-align: right; padding-right: 0.9em;" | 30 Mar 2010
|The two beams collided at 7&nbsp;TeV (3.5&nbsp;TeV per beam) in the LHC at 13:06 CEST, marking the start of the LHC research programme.
|-
| style="text-align: right; padding-right: 0.9em;" | 8 Nov 2010
|Start of the first run with lead ions.
|-
| style="text-align: right; padding-right: 0.9em;" | 6 Dec 2010
|End of the run with lead ions. Shutdown until early 2011.
|-
| style="text-align: right; padding-right: 0.9em;" | 13 Mar 2011
|Beginning of the 2011 run with proton beams.<ref>
{{cite news|date=13 March 2011|title=LHC sees first stable-beam 3.5 TeV collisions of 2011|url=http://www.symmetrymagazine.org/breaking/2011/03/13/lhc-sees-first-3-5-tev-collisions-of-2011/|publisher=symmetry breaking|access-date=2011-03-15}}</ref>
|-
| style="text-align: right; padding-right: 0.9em;" | 21 Apr 2011
|LHC becomes the world's highest-luminosity hadron accelerator achieving a peak luminosity of 4.67·10<sup>32</sup>&nbsp;cm<sup>−2</sup>s<sup>−1</sup>, beating the Tevatron's previous record of 4·10<sup>32</sup>&nbsp;cm<sup>−2</sup>s<sup>−1</sup> held for one year.<ref>{{cite press release |url=http://press.cern/press-releases/2011/04/lhc-sets-world-record-beam-intensity|title=LHC sets world record beam intensity |website=Media and Press Relations |publisher=CERN |date=22 April 2011|access-date=2016-11-13}}</ref>
|-
| style="text-align: right; padding-right: 0.9em;" | 24 May 2011
|ALICE reports that a Quark–gluon plasma has been achieved with earlier lead collisions.<ref name="plasma">{{cite web|url=https://www.nationalgeographic.com/science/article/110524-densest-matter-created-lhc-alice-big-bang-space-science|title=Densest Matter Created in Big-Bang Machine|website=National Geographic |date=2011-05-26 |first1=Ker |last1=Than |url-status=dead |archive-url=https://web.archive.org/web/20230607063520/https://www.nationalgeographic.com/science/article/110524-densest-matter-created-lhc-alice-big-bang-space-science |archive-date= Jun 7, 2023 }}</ref>
|-
| style="text-align: right; padding-right: 0.9em;" | 17 Jun 2011
|The high-luminosity experiments ATLAS and CMS reach 1 [[Inverse femtobarn|fb<sup>−1</sup>]] of collected data.<ref>{{cite press release |url=http://press.cern/press-releases/2011/06/lhc-achieves-2011-data-milestone|title=LHC achieves 2011 data milestone |website=Media and Press Relations |publisher=CERN |date=17 June 2011|access-date=2011-06-20}}</ref>
|-
| style="text-align: right; padding-right: 0.9em;" | 14 Oct 2011
|LHCb reaches 1 fb<sup>−1</sup> of collected data.<ref>{{cite web |url=http://www.quantumdiaries.org/2011/10/18/one-recorded-inverse-femtobarn/ |title=One Recorded Inverse Femtobarn!!! |author=Anna Phan |website=Quantum Diaries }}</ref>
|-
| style="text-align: right; padding-right: 0.9em;" | 23 Oct 2011
|The high-luminosity experiments ATLAS and CMS reach 5 fb<sup>−1</sup> of collected data.
|-
| style="text-align: right; padding-right: 0.9em;" | Nov 2011
|Second run with lead ions.
|-
| style="text-align: right; padding-right: 0.9em;" | 22 Dec 2011
|First new composite particle discovery, the χ<sub>b</sub> (3P) [[bottomonium]] meson, observed with proton–proton collisions in 2011.<ref name="dec 2011 particle">{{cite news|author=Jonathan Amos|url=https://www.bbc.co.uk/news/science-environment-16301908|title=LHC reports discovery of its first new particle|work=BBC News|date=22 December 2011}}</ref>
|-
| style="text-align: right; padding-right: 0.9em;" | 5 Apr 2012
|First collisions with stable beams in 2012 after the winter shutdown. The energy is increased to 4&nbsp;TeV per beam (8&nbsp;TeV in collisions).<ref>{{cite press release |url=http://press.cern/press-releases/2012/04/lhc-physics-data-taking-gets-underway-new-record-collision-energy-8tev|title=LHC physics data taking gets underway at new record collision energy of 8TeV |website=Media and Press Relations |publisher=CERN |date=5 April 2012|access-date=2016-11-13}}</ref>
|-
| style="text-align: right; padding-right: 0.9em;" | 4 Jul 2012
|First new elementary particle discovery, a new boson observed that is "consistent with" the theorized Higgs boson. (This has now been confirmed as the Higgs boson itself.<ref name="CERN 03-14-2013">{{cite news | url=http://home.web.cern.ch/about/updates/2013/03/new-results-indicate-new-particle-higgs-boson | title=New results indicate that new particle is a Higgs boson|publisher=CERN|date=14 March 2013|access-date=14 March 2013}}</ref>)
|-
| style="text-align: right; padding-right: 0.9em;" | 8 Nov 2012
| First observation of the very rare decay of the B<sub>s</sub> [[meson]] into two [[muon]]s (B<sub>s</sub><sup>0</sup> → μ<sup>+</sup>μ<sup>−</sup>), a major test of supersymmetry theories,<ref name="LCHb Nov 2012">{{cite news|last=Ghosh|first=Pallab|title=Popular physics theory running out of hiding places|url=https://www.bbc.co.uk/news/science-environment-20300100|access-date=14 November 2012|newspaper=BBC News|date=12 Nov 2012}}</ref> shows results at 3.5 sigma that match the Standard Model rather than many of its super-symmetrical variants.
|-
| style="text-align: right; padding-right: 0.9em;" | 20 Jan 2013
|Start of the first run colliding protons with lead ions.
|-
| style="text-align: right; padding-right: 0.9em;" | 11 Feb 2013
|End of the first run colliding protons with lead ions.
|-
| style="text-align: right; padding-right: 0.9em;" | 14 Feb 2013
|Beginning of the first long shutdown to prepare the collider for a higher energy and luminosity.<ref>{{cite press release |url=http://press.cern/press-releases/2012/12/first-lhc-protons-run-ends-new-milestone|title=The first LHC protons run ends with new milestone |website=Media and Press Relations |publisher=CERN |date=17 December 2012|access-date=10 March 2014}}</ref>
|-
! colspan="2"|Long Shutdown 1
|-
| style="text-align: right; padding-right: 0.9em;" | 7 Mar 2015
|Injection tests for Run 2 send protons towards LHCb & ALICE
|-
| style="text-align: right; padding-right: 0.9em;" | 5 Apr 2015
|Both beams circulated in the collider.<ref name="BBC" /> Four days later, a new record energy of 6.5&nbsp;TeV per proton was achieved.<ref>{{cite web|url=http://home.web.cern.ch/about/updates/2015/04/first-successful-beam-record-energy-65-tev|title=First successful beam at record energy of 6.5 TeV|publisher=CERN|date=10 April 2015|access-date=5 May 2015}}</ref>
|-
| style="text-align: right; padding-right: 0.9em;" | 20 May 2015
|Protons collided in the LHC at the record-breaking collision energy of 13&nbsp;TeV.<ref name="13TeVcollisions">{{cite web |url=https://home.cern/about/updates/2015/05/first-images-collisions-13-tev |title=First images of collisions at 13 TeV |first=Cian |last=O'Luanaigh |date=21 May 2015 |publisher=CERN}}</ref>
|-
| style="text-align: right; padding-right: 0.9em;" | 3 Jun 2015
|Start of delivering the physics data after almost two years offline for recommissioning.<ref name=":0" />
|-
| style="text-align: right; padding-right: 0.9em;" | 4 Nov 2015
|End of proton collisions in 2015, start of preparations for ion collisions.
|-
| style="text-align: right; padding-right: 0.9em;" | Nov 2015
|Ion collisions at a record-breaking energy of more than 1&nbsp;PeV (10<sup>15</sup> eV)<ref>{{cite web|url=https://home.cern/news/opinion/physics/new-energy-frontier-heavy-ions|title=A new energy frontier for heavy ions|access-date=2 April 2021}}</ref>
|-
| style="text-align: right; padding-right: 0.9em;" | 13 Dec 2015
|End of ion collisions in 2015
|-
| style="text-align: right; padding-right: 0.9em;" | 23 Apr 2016
|Data-taking in 2016 begins
|-
| style="text-align: right; padding-right: 0.9em; white-space: nowrap;" | 29 June 2016
|The LHC achieves a luminosity of 1.0 · 10<sup>34</sup>&nbsp;cm<sup>−2</sup>s<sup>−1</sup>, its design value.<ref name="designlumireached" /> Further improvements over the year increased the luminosity to 40% above the design value.<ref name="2016lumi" />
|-
| style="text-align: right; padding-right: 0.9em;" | 26 Oct 2016
|End of 2016 proton–proton collisions
|-
| style="text-align: right; padding-right: 0.9em;" | 10 Nov 2016
|Beginning of 2016 proton–lead collisions
|-
| style="text-align: right; padding-right: 0.9em;" | 3 Dec 2016
|End of 2016 proton–lead collisions
|-
| style="text-align: right; padding-right: 0.9em;" | 24 May 2017
|Start of 2017 proton–proton collisions. During 2017, the luminosity increased to twice its design value.<ref name="endof2017" />
|-
| style="text-align: right; padding-right: 0.9em;" | 10 Nov 2017
|End of regular 2017 proton–proton collision mode.<ref name="endof2017">{{cite news|url=https://home.cern/about/updates/2017/11/record-luminosity-well-done-lhc|title=Record luminosity: well done LHC|date=15 Nov 2017|access-date=2 Dec 2017}}</ref>
|-
| style="text-align: right; padding-right: 0.9em;" | 17 Apr 2018
|Start of 2018 proton–proton collisions.
|-
| style="text-align: right; padding-right: 0.9em;" | 12 Nov 2018
|End of 2018 proton operations at CERN.<ref name="endof2018">{{cite web|url=https://home.cern/news/news/accelerators/lhc-report-another-run-over-and-ls2-has-just-begun|title=LHC Report: Another run is over and LS2 has just begun…|website=CERN|date=10 April 2024 }}</ref>
|-
| style="text-align: right; padding-right: 0.9em;" | 3 Dec 2018
|End of 2018 lead-ion run.<ref name="endof2018"/>
|-
| style="text-align: right; padding-right: 0.9em;" | 10 Dec 2018
|End of 2018 physics operation and start of Long Shutdown 2.<ref name="endof2018"/>
|-
! colspan="2"|Long Shutdown 2
|-
| style="text-align: right; padding-right: 0.9em;" | 22 Apr 2022
|LHC becomes operational again.<ref>{{cite press release |url=https://home.cern/news/news/accelerators/large-hadron-collider-restarts|title=Large Hadron Collider restarts |website=Media and Press Relations |publisher=CERN |date=22 April 2022|access-date=8 November 2022}}</ref>
|-
|20 Mar 2023
|For the first time in 5 years, the scientists are observing lead ions.<ref>{{Cite web |date=2024-07-18 |title=CERN highlights in 2023 |url=https://home.cern/news/news/cern/cern-highlights-2023 |access-date=2024-07-25 |website=CERN |language=en}}</ref>
|-
|5 Apr 2024
|LHC reaches its first stable beams in 2024.<ref>{{Cite web |date=2024-07-18 |title=Large Hadron Collider reaches its first stable beams in 2024 |url=https://home.cern/news/news/accelerators/large-hadron-collider-reaches-its-first-stable-beams-2024 |access-date=2024-07-25 |website=CERN |language=en}}</ref>
|}

== Findings and discoveries ==

An initial focus of research was to investigate the possible existence of the [[Higgs boson]], a key part of the [[Standard Model]] of physics which was predicted by theory, but had not yet been observed before due to its high mass and elusive nature. CERN scientists estimated that, if the Standard Model was correct, the LHC would produce several Higgs bosons every minute, allowing physicists to finally confirm or disprove the Higgs boson's existence. In addition, the LHC allowed the search for [[Superpartner|supersymmetric particles]] and other hypothetical particles as possible unknown areas of physics.<ref name="LHCbooklet"/> Some extensions of the Standard Model predict additional particles, such as the heavy [[W' and Z' bosons|W' and Z' gauge bosons]], which are also estimated to be within reach of the LHC to discover.<ref>{{cite news| author=P. Rincon| url=http://news.bbc.co.uk/1/hi/sci/tech/8685541.stm| title=LHC particle search 'nearing', says physicist| publisher=BBC News| date=17 May 2010}}</ref>

=== First run (data taken 2009–2013) ===

The first physics results from the LHC, involving 284 collisions which took place in the ALICE detector, were reported on 15&nbsp;December 2009.<ref name="first science 2009" /> The results of the first proton–proton collisions at energies higher than Fermilab's Tevatron proton–antiproton collisions were published by the CMS collaboration in early February 2010, yielding greater-than-predicted charged-hadron production.<ref name="first proton-proton 2010">{{cite journal|author=V. Khachatryan ''et al.'' (CMS collaboration)|year=2010|title=Transverse momentum and pseudorapidity distributions of charged hadrons in pp collisions at {{radical|s}}&nbsp;=&nbsp;0.9 and 2.36&nbsp;TeV|journal=[[Journal of High Energy Physics]]|volume=2010|issue=2|pages=1–35|arxiv=1002.0621|bibcode=2010JHEP...02..041K|doi=10.1007/JHEP02(2010)041|doi-access=free}}</ref>

After the first year of data collection, the LHC experimental collaborations started to release their preliminary results concerning searches for new physics beyond the Standard Model in proton–proton collisions.<ref name="CMS-XD">{{cite journal|author=V. Khachatryan ''et al.'' (CMS collaboration)|year=2011|title=Search for Microscopic Black Hole Signatures at the Large Hadron Collider|journal=[[Physics Letters B]]|volume=697|issue=5|pages=434–453 |arxiv=1012.3375 |bibcode= 2011PhLB..697..434C|doi=10.1016/j.physletb.2011.02.032|doi-access=free}}</ref><ref name="CMS-SUSY">{{cite journal|author=V. Khachatryan ''et al.'' (CMS collaboration)|year=2011|title=Search for Supersymmetry in pp Collisions at 7 TeV in Events with Jets and Missing Transverse Energy|journal=[[Physics Letters B]]|volume=698|issue=3|pages=196–218 |arxiv=1101.1628 |bibcode=2011PhLB..698..196C |doi=10.1016/j.physletb.2011.03.021 |doi-access=free}}</ref><ref name="ATLAS-SUSY1">{{cite journal|author=G. Aad ''et al.'' ([[ATLAS experiment|ATLAS collaboration]])|year=2011|title=Search for supersymmetry using final states with one lepton, jets, and missing transverse momentum with the ATLAS detector in {{radical|s}}&nbsp;=&nbsp;7 TeV pp|journal=[[Physical Review Letters]]|volume=106|issue=13|pages=131802|arxiv=1102.2357|bibcode= 2011PhRvL.106m1802A|doi=10.1103/PhysRevLett.106.131802|pmid=21517374|doi-access=free}}</ref><ref name="ATLAS-SUSY2">{{cite journal|author=G. Aad ''et al.'' (ATLAS collaboration)|year=2011|title=Search for squarks and gluinos using final states with jets and missing transverse momentum with the ATLAS detector in {{radical|s}}&nbsp;=&nbsp;7&nbsp;TeV proton–proton collisions|journal=[[Physics Letters B]]|volume=701|issue=2|pages=186–203|arxiv=1102.5290|bibcode= 2011PhLB..701..186A|doi=10.1016/j.physletb.2011.05.061|doi-access=free}}</ref> No evidence of new particles was detected in the 2010 data. As a result, bounds were set on the allowed parameter space of various extensions of the Standard Model, such as models with [[large extra dimensions]], constrained versions of the [[Minimal Supersymmetric Standard Model]], and others.<ref>Chalmers, M. [http://physicsworld.com/cws/article/indepth/44805 Reality check at the LHC], [http://physicsworld.com/ physicsworld.com], 18 January 2011</ref><ref>McAlpine, K. [http://physicsworld.com/cws/article/news/45182 Will the LHC find supersymmetry?] {{Webarchive|url=https://web.archive.org/web/20110225101256/http://physicsworld.com/cws/article/news/45182 |date=25 February 2011 }}, [http://physicsworld.com/ physicsworld.com], 22 February 2011</ref><ref>{{cite journal|author=Geoff Brumfiel|year=2011|title=Beautiful theory collides with smashing particle data|journal=[[Nature (journal)|Nature]]|volume=471|issue=7336|pages=13–14|bibcode=2011Natur.471...13B|doi=10.1038/471013a|pmid=21368793|doi-access=free}}</ref>

On 24 May 2011, it was reported that quark–gluon plasma (the densest matter thought to exist besides [[black hole]]s) had been created in the LHC.<ref name="plasma" />

[[File:BosonFusion-Higgs.svg|thumb|right|A [[Feynman diagram]] of one way the Higgs boson may be produced at the LHC. Here, two quarks each emit a [[W and Z bosons|W or Z boson]], which combine to make a neutral Higgs.]]
Between July and August 2011, results of searches for the [[Higgs boson]] and for exotic particles, based on the data collected during the first half of the 2011 run, were presented in conferences in Grenoble<ref>{{cite press release |url=http://press.cern/press-releases/2011/07/lhc-experiments-present-their-latest-results-europhysics-conference-high|title=LHC experiments present their latest results at Europhysics Conference on High Energy Physics |website=Media and Press Relations |publisher=CERN |date=21 July 2011|access-date=13 November 2016}}</ref> and Mumbai.<ref>{{cite press release |url=http://press.cern/press-releases/2011/08/lhc-experiments-present-latest-results-mumbai-conference|title=LHC experiments present latest results at Mumbai conference |website=Media and Press Relations |publisher=CERN |date=22 August 2011|access-date=13 November 2016}}</ref> In the latter conference, it was reported that, despite hints of a Higgs signal in earlier data, ATLAS and CMS exclude with 95% confidence level (using the [[CLs upper limits|CLs]] method) the existence of a Higgs boson with the properties predicted by the Standard Model over most of the mass region between 145 and 466&nbsp;GeV.<ref>{{cite news|author=Pallab Ghosh|url=https://www.bbc.co.uk/news/science-environment-14596367|title=Higgs boson range narrows at European collider|publisher=BBC News|date=22 August 2011}}</ref> The searches for new particles did not yield signals either, allowing to further constrain the parameter space of various extensions of the Standard Model, including its supersymmetric extensions.<ref>{{cite news|author=Pallab Ghosh|url=https://www.bbc.co.uk/news/science-environment-14680570|title=LHC results put supersymmetry theory 'on the spot'|publisher=BBC News|date=27 August 2011}}</ref><ref>{{cite web |url=http://www.symmetrymagazine.org/breaking/2011/08/29/lhcb-experiment-sees-standard-model-physics/ |title=LHCb experiment sees Standard Model physics |publisher=SLAC/Fermilab |website=Symmetry Magazine |date=29 August 2011 |access-date=1 September 2011}}</ref>

On 13 December 2011, CERN reported that the Standard Model Higgs boson, if it exists, is most likely to have a mass constrained to the range 115–130&nbsp;GeV.
Both the CMS and ATLAS detectors have also shown intensity peaks in the 124–125&nbsp;GeV range, consistent with either background noise or the observation of the Higgs boson.<ref>{{cite press release |url=http://press.cern/press-releases/2011/12/atlas-and-cms-experiments-present-higgs-search-status|title=ATLAS and CMS experiments present Higgs search status |website=Media and Press Relations |publisher=CERN |date=13 December 2011|access-date=13 November 2016}}</ref>

On 22 December 2011, it was reported that a new composite particle had been observed, the χ<sub>b</sub> (3P) bottomonium state.<ref name="dec 2011 particle" />

On 4 July 2012, both the CMS and ATLAS teams announced the discovery of a boson in the mass region around 125–126&nbsp;GeV, with a statistical significance at the level of 5 [[Standard deviation|sigma]] each. This meets the formal level required to announce a new particle. The observed properties were consistent with the Higgs boson, but scientists were cautious as to whether it is formally identified as actually being the Higgs boson, pending further analysis.<ref name=cern1207>{{cite press release |url=http://press.cern/press-releases/2012/07/cern-experiments-observe-particle-consistent-long-sought-higgs-boson |title=CERN experiments observe particle consistent with long-sought Higgs boson |website=Media and Press Relations |publisher=CERN |date=4 July 2012 |access-date=9 November 2016 |df=dmy }}</ref> On 14 March 2013, CERN announced confirmation that the observed particle was indeed the predicted Higgs boson.<ref>{{cite web |date=14 March 2013 |title=Now confident: CERN physicists say new particle is Higgs boson (Update 3) |url=https://phys.org/news/2013-03-confident-cern-physicists-higgs-boson.html |publisher=Phys Org |access-date=4 December 2019}}</ref>

On 8 November 2012, the LHCb team reported on an experiment seen as a "golden" test of [[supersymmetry]] theories in physics,<ref name="LCHb Nov 2012" /> by measuring the very rare decay of the <math>B_s</math> meson into two muons (<math>B_s^0\rightarrow\mu^+\mu^-</math>). The results, which match those predicted by the non-supersymmetrical Standard Model rather than the predictions of many branches of supersymmetry, show the decays are less common than some forms of supersymmetry predict, though could still match the predictions of other versions of supersymmetry theory. The results as initially drafted are stated to be short of proof but at a relatively high 3.5 sigma level of significance.<ref>{{cite journal |doi=10.1103/PhysRevLett.110.021801 | pmid=23383888 | bibcode=2013PhRvL.110b1801A | volume=110 | issue=2 | title=First Evidence for the Decay <math>B_s^0\rightarrow\mu^+\mu^-</math> |author=LHCb Collaboration |page=021801 |date=7 January 2013 | journal=Physical Review Letters| arxiv=1211.2674 | s2cid=13103388 }}</ref> The result was later confirmed by the CMS collaboration.<ref name="cmsbsmumu">{{cite journal |author=CMS collaboration |date=5 September 2013 |title= Measurement of the <math>B_s^0\rightarrow\mu^+\mu^-</math> Branching Fraction and Search for <math>B^0\rightarrow\mu^+\mu^-</math> with the CMS Experiment |journal= Physical Review Letters|volume= 111|issue= 10|page= 101804|doi=10.1103/PhysRevLett.111.101804 |doi-access=free |arxiv = 1307.5025 |bibcode = 2013PhRvL.111j1804C |pmid=25166654}}</ref>

In August 2013, the LHCb team revealed an anomaly in the angular distribution of [[B meson]] decay products which could not be predicted by the Standard Model; this anomaly had a statistical certainty of 4.5 sigma, just short of the 5 sigma needed to be officially recognized as a discovery. It is unknown what the cause of this anomaly would be, although the [[Z' boson]] has been suggested as a possible candidate.<ref name="newphysics">{{cite web|url=http://news.discovery.com/space/hints-of-new-physics-detected-in-the-lhc-130802.htm|title=Hints of New Physics Detected in the LHC?|date=10 May 2017}}</ref>

On 19 November 2014, the LHCb experiment announced the discovery of two new heavy subatomic particles, {{Subatomic particle|bottom xi'-}} and {{Subatomic particle|bottom xi*-}}. Both of them are baryons that are composed of one bottom, one down, and one strange quark. They are excited states of the bottom [[Xi baryon]].<ref>[http://www.cbc.ca/news/technology/new-subatomic-particles-predicted-by-canadians-found-at-cern-1.2840199 New subatomic particles predicted by Canadians found at CERN], 19 November 2014</ref><ref>{{cite press release |url=http://press.cern/press-releases/2014/11/lhcb-experiment-observes-two-new-baryon-particles-never-seen |title=LHCb experiment observes two new baryon particles never seen before |date=19 November 2014 |website=Media and Press Relations |publisher=CERN |access-date=19 November 2014}}</ref>

The [[LHCb|LHCb collaboration]] has observed multiple exotic hadrons, possibly [[pentaquarks]] or [[tetraquarks]], in the Run 1 data.
On 4 April 2014, the collaboration confirmed the existence of the tetraquark candidate [[Z(4430)]] with a significance of over 13.9 sigma.<ref>{{cite web|first=Cian|last=O'Luanaigh|date=9 April 2014|title=LHCb confirms existence of exotic hadrons|url=http://home.web.cern.ch/about/updates/2014/04/lhcb-confirms-existence-exotic-hadrons|publisher=CERN|access-date=4 April 2016}}</ref><ref name="LHCb">{{cite journal|first=R.|last=Aaij|display-authors=etal|collaboration=LHCb collaboration|date=4 June 2014|title=Observation of the resonant character of the Z(4430)− state|journal=[[Physical Review Letters]]|volume=112 |issue=21 |page=222002|arxiv=1404.1903|bibcode=2014PhRvL.112v2002A|doi=10.1103/PhysRevLett.112.222002|doi-access=free|pmid=24949760}}</ref> On 13&nbsp;July 2015, results consistent with pentaquark states in the decay of [[bottom Lambda baryon]]s (Λ{{su|p=0|b=b}}) were reported.<ref name="LHCb2015">{{cite journal|first=R.|last=Aaij|display-authors=etal|collaboration=[[LHCb|LHCb collaboration]]|date=12 August 2015|title=Observation of J/ψp resonances consistent with pentaquark states in Λ{{su|p=0|b=b}}→J/ψK<sup>−</sup>p decays|journal=[[Physical Review Letters]]|volume=115 |issue=7|pages=072001|doi=10.1103/PhysRevLett.115.072001|pmid=26317714|doi-access=free|arxiv = 1507.03414|bibcode = 2015PhRvL.115g2001A}}</ref><ref>{{cite press release |url=http://press.cern/press-releases/2015/07/cerns-lhcb-experiment-reports-observation-exotic-pentaquark-particles |title=CERN's LHCb experiment reports observation of exotic pentaquark particles |website=Media and Press Relations |publisher=CERN |access-date=28 August 2015}}</ref><ref>{{cite news |last=Rincon |first=Paul |url=https://www.bbc.com/news/science-environment-33517492 |title=Large Hadron Collider discovers new pentaquark particle |work=BBC News |date=1 July 2015 |access-date=14 July 2015 }}</ref>

On 28 June 2016, the collaboration announced four tetraquark-like particles decaying into a J/ψ and a φ meson, only one of which was well established before (X(4274), X(4500) and X(4700) and [[Y(4140)|X(4140)]]).<ref>{{cite journal |last=Aaij |first=R. |display-authors=etal |collaboration=LHCb collaboration |year=2017 |title=Observation of J/ψφ structures consistent with exotic states from amplitude analysis of B<sup>+</sup>→J/ψφK<sup>+</sup> decays |arxiv=1606.07895 |doi=10.1103/PhysRevLett.118.022003 |pmid=28128595 |bibcode=2017PhRvL.118b2003A |volume=118 |issue=2 |page=022003 |journal=Physical Review Letters|s2cid=206284149 }}</ref><ref>{{cite journal |last=Aaij |first=R. |display-authors=etal |collaboration=LHCb collaboration |year=2017 |title=Amplitude analysis of B<sup>+</sup>→J/ψφK<sup>+</sup> decays  |arxiv=1606.07898 |doi=10.1103/PhysRevD.95.012002 |volume=95 |issue=1 |page=012002 |journal=Physical Review D|bibcode=2017PhRvD..95a2002A|s2cid=73689011 }}</ref>

In December 2016, ATLAS presented a measurement of the W boson mass, researching the precision of analyses done at the Tevatron.<ref name="wmass">{{cite web|url=http://atlas.cern/updates/physics-briefing/measuring-w-boson-mass |title=ATLAS releases first measurement of the W mass using LHC data|date=13 December 2016|access-date=27 January 2017}}</ref>

=== Second run (2015–2018) ===
<!-- Please only put here results that use Run II (13 TeV) data. Check the reported centre of mass energy sqrt(s). If it's 7 and/or 8 TeV, it belongs in Run I. Don't put the pentaquarks here, for example. -->
At the conference EPS-HEP 2015 in July, the collaborations presented first cross-section measurements of several particles at the higher collision energy.

On 15 December 2015, the [[ATLAS experiment|ATLAS]] and CMS experiments both reported a number of preliminary results for Higgs physics, supersymmetry (SUSY) searches and [[exotic particle|exotics]] searches using 13&nbsp;TeV proton collision data. Both experiments saw a moderate excess around 750&nbsp;GeV in the two-photon [[invariant mass]] spectrum,<ref name="NYT-20151215">{{cite news |last =Overbye |first=Dennis |author-link=Dennis Overbye |title=Physicists in Europe Find Tantalizing Hints of a Mysterious New Particle |url=https://www.nytimes.com/2015/12/16/science/physicists-in-europe-find-tantalizing-hints-of-a-mysterious-new-particle.html |date=15 December 2015 |work=[[New York Times]] |access-date=15 December 2015 }}</ref><ref name="CMS-750GeV">{{cite web |author=CMS Collaboration |title=Search for new physics in high mass diphoton events in proton–proton collisions at 13&nbsp;TeV |url=http://cms-results.web.cern.ch/cms-results/public-results/preliminary-results/EXO-15-004/index.html |date=15 December 2015 |website=[[Compact Muon Solenoid]] |access-date=2 January 2016 }}</ref><ref name="ATLAS-750GeV">{{cite web |title=Search for resonances decaying to photon pairs in 3.2&nbsp;fb<sup>−1</sup> of pp collisions at √s = 13&nbsp;TeV with the ATLAS detector |url=http://cdsweb.cern.ch/record/2114853/files/ATLAS-CONF-2015-081.pdf |date=15 December 2015 |author=ATLAS Collaboration |access-date=2 January 2016 |author-link=ATLAS Collaboration }}</ref> but the experiments did not confirm the existence of [[750 GeV diphoton excess|the hypothetical particle]] in an August 2016 report.<ref>{{cite web |url=https://cds.cern.ch/record/2205245/files/EXO-16-027-pas.pdf |title=CMS Physics Analysis Summary |author=CMS Collaboration |publisher=CERN |access-date=4 August 2016}}</ref><ref name="NYT-20160805">{{cite news |last=Overbye |first=Dennis |author-link=Dennis Overbye |title=The Particle That Wasn't |url=https://www.nytimes.com/2016/08/05/science/cern-large-hadron-collider-particle.html |date=5 August 2016 |work=[[New York Times]] |access-date=5 August 2016 }}</ref><ref>{{cite press release |url=https://press.cern/press-releases/2016/08/chicago-sees-floods-lhc-data-and-new-results-ichep-2016-conference|title=Chicago sees floods of LHC data and new results at the ICHEP 2016 conference |website=Media and Press Relations |publisher=CERN |date=5 August 2015|access-date=5 August 2015}}</ref>

In July 2017, many analyses based on the large dataset collected in 2016 were shown. The properties of the Higgs boson were studied in more detail and the precision of many other results was improved.<ref name="CERN_EPS2017">{{cite press release|url=https://press.cern/update/2017/07/lhc-experiments-delve-deeper-precision|title=LHC experiments delve deeper into precision|date=11 July 2017|website=Media and Press Relations|publisher=CERN|access-date=23 July 2017|archive-date=14 July 2017|archive-url=https://web.archive.org/web/20170714090456/http://press.cern/update/2017/07/lhc-experiments-delve-deeper-precision|url-status=dead}}</ref>

As of March 2021, the LHC experiments have discovered 59 new hadrons in the data collected during the first two runs.<ref>{{cite web |url=https://home.cern/news/news/physics/59-new-hadrons-and-counting |first1=Piotr |last1=Traczyk |title=59 new hadrons and counting |publisher=CERN |date=3 March 2021 |access-date=23 July 2021 }}</ref>

=== Third run (2022 – present) ===
	
The third run of the LHC began in July of 2022, after more than three years of upgrades, and is planned to last until July of 2026.<ref>{{Cite web |date=2024-11-29 |title=New schedule for CERN's accelerators |url=https://home.web.cern.ch/news/news/accelerators/new-schedule-cerns-accelerators |access-date=2024-12-01 |website=CERN |language=en}}</ref><ref>{{Cite web |date=2024-11-29 |title=Run 3: an opportunity to expand the LHC physics programme |url=https://home.cern/press/2022/run-3 |access-date=2024-12-01 |website=CERN |language=en}}</ref>

On 5 July 2022, LHCb reported the discovery of a new type of [[pentaquark]] made up of a charm quark and a charm antiquark and an up, a down and a strange quark, observed in an analysis of decays of charged B mesons.<ref name=":1">{{Cite web |date=2024-11-29 |title=LHCb discovers three new exotic particles |url=https://home.cern/news/news/physics/lhcb-discovers-three-new-exotic-particles |access-date=2024-12-01 |website=CERN |language=en}}</ref><ref>{{cite web|url=https://eandt.theiet.org/content/articles/2022/07/large-hadron-collider-project-discovers-three-new-exotic-particles/ |title=Large Hadron Collider project discovers three new exotic particles  |publisher=E&T Magazine |date=2022-07-05 |accessdate=2022-08-01 |url-status=live |archive-url=https://web.archive.org/web/20220808162016/https://eandt.theiet.org/content/articles/2022/07/large-hadron-collider-project-discovers-three-new-exotic-particles/ |archive-date= Aug 8, 2022 }}</ref> The first ever pair of [[Tetraquark|tetraquarks]] was also reported.<ref name=":1" />

On 18 September 2024, ATLAS reported the first observation of [[quantum entanglement]] between [[Quark|quarks]], with it also being the highest-energy observation of entanglement so far.<ref>{{Cite journal |last1=The ATLAS Collaboration |last2=Aad |first2=G. |last3=Abbott |first3=B. |last4=Abeling |first4=K. |last5=Abicht |first5=N. J. |last6=Abidi |first6=S. H. |last7=Aboulhorma |first7=A. |last8=Abramowicz |first8=H. |last9=Abreu |first9=H. |last10=Abulaiti |first10=Y. |last11=Acharya |first11=B. S. |last12=Bourdarios |first12=C. Adam |last13=Adamczyk |first13=L. |last14=Addepalli |first14=S. V. |last15=Addison |first15=M. J. |date=2024-09-19 |title=Observation of quantum entanglement with top quarks at the ATLAS detector |journal=Nature |language=en |volume=633 |issue=8030 |pages=542–547 |doi=10.1038/s41586-024-07824-z |issn=0028-0836 |pmc=11410654 |pmid=39294352}}</ref><ref>{{Cite journal |last=Garisto |first=Dan |date=2024-09-26 |title=Quantum feat: physicists observe entangled quarks for first time |url=https://www.nature.com/articles/d41586-024-02973-7 |journal=Nature |language=en |volume=633 |issue=8031 |pages=746–747 |doi=10.1038/d41586-024-02973-7 |bibcode=2024Natur.633..746G |issn=0028-0836}}</ref>

== Future plans ==

=== "High-luminosity" upgrade ===
{{Main|High Luminosity Large Hadron Collider}}

After some years of running, any particle physics experiment typically begins to suffer from [[diminishing returns]]: as the key results reachable by the device begin to be completed, later years of operation discover proportionately less than earlier years. A common response is to upgrade the devices involved, typically in collision energy, [[Luminosity (scattering theory)|luminosity]], or improved detectors. In addition to a possible increase to 14&nbsp;TeV collision energy, a luminosity upgrade of the LHC, called the High Luminosity Large Hadron Collider, started in June 2018 that will boost the accelerator's potential for new discoveries in physics, starting in 2027.<ref>{{cite web|url=https://home.cern/news/news/accelerators/new-schedule-lhc-and-its-successor |website=CERN |title=A new schedule for the LHC and its successor|date=13 December 2019 |url-status=live |archive-url=https://web.archive.org/web/20230529053259/https://home.cern/news/news/accelerators/new-schedule-lhc-and-its-successor |archive-date= May 29, 2023 }}</ref> The upgrade aims at increasing the luminosity of the machine by a factor of 10, up to 10<sup>35</sup>&nbsp;cm<sup>−2</sup>s<sup>−1</sup>, providing a better chance to see rare processes and improving statistically marginal measurements.<ref name="autogenerated1"/>

=== Proposed Future Circular Collider ===
CERN has several preliminary designs for a [[Future Circular Collider]] (FCC)—which would be the most powerful particle accelerator ever built—with different types of collider ranging in cost from around €9&nbsp;billion (US$10.2&nbsp;billion) to €21&nbsp;billion. It would use the LHC ring as preaccelerator, similar to how the LHC uses the smaller Super Proton Synchrotron. It is CERN's opening bid in a priority-setting process called the European Strategy for Particle Physics Update, and will affect the field's future well into the second half of the century. As of 2023, no fixed plan exists and it is unknown if the construction will be funded.<ref>{{cite news|url=https://scitechdaily.com/future-circular-collider-the-race-to-build-the-worlds-most-powerful-particle-collider/ |website=SciTechDaily |title=Future Circular Collider: The Race To Build the World's Most Powerful Particle Collider|date=7 April 2023|access-date=11 June 2023}}</ref>

== Safety of particle collisions ==
{{Main|Safety of high-energy particle collision experiments}}

The experiments at the Large Hadron Collider sparked fears that the particle collisions might produce doomsday phenomena, involving the production of stable [[micro black hole|microscopic black holes]] or the creation of hypothetical particles called [[strangelet]]s.<ref name="CosmicLog-2September2008">{{cite web |author=Alan Boyle |date=2 September 2008 |url=http://cosmiclog.nbcnews.com/_news/2008/09/02/4350490-courts-weigh-doomsday-claims |title=Courts weigh doomsday claims |website=Cosmic Log |publisher=[[MSNBC]] |access-date=28 September 2009 |archive-date=18 October 2015 |archive-url=https://web.archive.org/web/20151018133337/http://cosmiclog.nbcnews.com/_news/2008/09/02/4350490-courts-weigh-doomsday-claims |url-status=dead }}</ref> Two CERN-commissioned safety reviews examined these concerns and concluded that the experiments at the LHC present no danger and that there is no reason for concern,<ref name="2003SafetyReport">{{cite web |author1=J.-P. Blaizot |author2=J. Iliopoulos |author3=J. Madsen |author4=G.G. Ross |author5=P. Sonderegger |author6=H.-J. Specht |year=2003 |url=https://cds.cern.ch/record/613175/files/CERN-2003-001.pdf |title=Study of Potentially Dangerous Events During Heavy-Ion Collisions at the LHC |publisher=CERN |access-date=28 September 2009}}</ref><ref name="LSAGreport">{{cite journal |first1=J. |last1=Ellis |first2=G. |last2=Giudice |first3=M.L. |last3=Mangano |first4=T. |last4=Tkachev |first5=U. |last5=Wiedemann |year=2008 |title=Review of the Safety of LHC Collisions |journal=[[Journal of Physics G]]|volume=35 |issue=11 |page=115004 |arxiv=0806.3414 |bibcode=2008JPhG...35k5004E |doi=10.1088/0954-3899/35/11/115004|s2cid=53370175 }}</ref><ref name=SummarySafety>{{cite press release |year=2008 |url=http://press.cern/backgrounders/safety-lhc |title=The safety of the LHC |website=Media and Press Relations |publisher=CERN |access-date=28 September 2009}}</ref> a conclusion endorsed by the [[American Physical Society]].<ref name="APS-Statement">{{cite web |url=http://www.aps.org/units/dpf/governance/reports/upload/lhc_saftey_statement.pdf |title=Statement by the Executive Committee of the DPF on the Safety of Collisions at the Large Hadron Collider |author=Division of Particles & Fields |publisher=[[American Physical Society]] |access-date=28 September 2009 |url-status=dead |archive-url=https://web.archive.org/web/20091024184048/http://www.aps.org/units/dpf/governance/reports/upload/lhc_saftey_statement.pdf |archive-date=24 October 2009 }}</ref>

The reports also noted that the physical conditions and collision events that exist in the LHC and similar experiments occur naturally and routinely in the [[universe]] without hazardous consequences,<ref name="LSAGreport"/> including [[ultra-high-energy cosmic ray]]s observed to impact Earth with energies far higher than those in any human-made collider, like the [[Oh-My-God particle]] which had 320 million TeV of energy, and a collision energy tens of times more than the most energetic collisions produced in the LHC.

== Popular culture ==
<!--
DEAR EDITOR. This is not a trivia list, Please write prose and include notable occurrences. If unsure check the talk page and archives first. Thank you.
-->

The Large Hadron Collider gained a considerable amount of attention from outside the scientific community and its progress is followed by most popular science media. The LHC has also inspired works of fiction including novels, TV series, video games and films.

CERN employee [[Katherine McAlpine]]'s "Large Hadron Rap"<ref>{{cite web|author=Katherine McAlpine|date=28 July 2008|title=Large Hadron Rap| url=https://www.youtube.com/watch?v=j50ZssEojtM | archive-url=https://ghostarchive.org/varchive/youtube/20211030/j50ZssEojtM| archive-date=2021-10-30|publisher=[[YouTube]]| access-date=8 May 2011
}}{{cbignore}}</ref> surpassed 8&nbsp;million [[YouTube]] views as of 2022.<ref name="Telegraph02/09/2008">{{cite news| author=Roger Highfield| date=6 September 2008| title=Rap about world's largest science experiment becomes YouTube hit| url=https://www.telegraph.co.uk/earth/main.jhtml?xml=/earth/2008/08/26/scirap126.xml| archive-url=https://web.archive.org/web/20080828220809/http://www.telegraph.co.uk/earth/main.jhtml?xml=/earth/2008/08/26/scirap126.xml| url-status=dead| archive-date=28 August 2008| work=[[Daily Telegraph]]| access-date=28 September 2009| location=London| author-link=Roger Highfield}}</ref><ref>{{cite web| author=Jennifer Bogo| date=1 August 2008| url=http://www.popularmechanics.com/blogs/science_news/4276090.html| title=Large Hadron Collider rap teaches particle physics in 4 minutes| website=[[Popular Mechanics]]| access-date=28 September 2009| archive-date=17 September 2008| archive-url=https://web.archive.org/web/20080917132230/http://www.popularmechanics.com/blogs/science_news/4276090.html| url-status=dead}}</ref>

The band [[Les Horribles Cernettes]] was founded by women from CERN. The name was chosen so to have the same initials as the LHC.<ref name="CernettesNYT">{{cite news| author=Malcolm W Brown|date=29 December 1998| title=Physicists Discover Another Unifying Force: Doo-Wop| url=http://musiclub.web.cern.ch/MusiClub/bands/cernettes/Press/NYT.pdf| work=[[New York Times]]|access-date=21 September 2010}}</ref><ref name="CernettesWired">{{cite news| author=Heather McCabe| date=10 February 1999|title=Grrl Geeks Rock Out| url=http://musiclub.web.cern.ch/MusiClub/bands/cernettes/Press/Wired.pdf|work=[[Wired News]]|access-date=21 September 2010}}</ref>
<!-- PLEASE NOTE: This is not a trivia list; please see the comment at the top of this section. -->

[[National Geographic Channel]]'s ''[[World's Toughest Fixes]]'', Season 2 (2010), Episode 6 "Atom Smasher" features the replacement of the last superconducting magnet section in the repair of the collider after the 2008 quench incident. The episode includes actual footage from the repair facility to the inside of the collider, and explanations of the function, engineering, and purpose of the LHC.<ref>{{Cite episode |title=Atom Smashers |url=http://natgeotv.com.au/tv/world%27s-toughest-fixes/episode.aspx?id=100 |access-date=15 June 2014 |series=World's Toughest Fixes |series-link=World's Toughest Fixes |network=[[National Geographic Channel]] |season=2 |number=6 |url-status=dead |archive-url=https://web.archive.org/web/20140502010242/http://natgeotv.com.au/tv/world%27s-toughest-fixes/episode.aspx?id=100 |archive-date=2 May 2014 |df=dmy-all }}</ref>

The song "Munich" on the 2012 studio album ''[[Scars & Stories]]'' by [[The Fray]] is inspired by the Large Hadron Collider. Lead singer [[Isaac Slade]] said in an interview with ''[[The Huffington Post]]'', "There's this large particle collider out in Switzerland that is kind of helping scientists peel back the curtain on what creates gravity and mass. Some very big questions are being raised, even some things that Einstein proposed, that have just been accepted for decades are starting to be challenged. They're looking for the God Particle, basically, the particle that holds it all together. That song is really just about the mystery of why we're all here and what's holding it all together, you know?" <ref>{{cite web |url=https://www.huffpost.com/entry/emthe-wayman-tisdale-stor_b_1218849 |title=The Wayman Tisdale Story and Scars & Stories: Conversations with Director Brian Schodorf and The Fray's Isaac Slade |last=Ragogna |first=Mike |date=20 January 2012 |access-date=23 April 2022}}</ref>

The Large Hadron Collider was the focus of the 2012 student film [[Decay (2012 film)|''Decay'']], with the movie being filmed on location in CERN's maintenance tunnels.<ref>{{cite web |url=http://www.popsci.com/science/article/2012-10/physics-students-film-zombie-movie-large-hadron-collider |title=Large Hadron Collider Unleashes Rampaging Zombies |last=Boyle |first=Rebecca |date=31 October 2012 |access-date=22 November 2012}}</ref>

===Fiction===
The novel ''[[Angels & Demons]]'', by [[Dan Brown]], involves [[antimatter]] created at the LHC to be used in a [[antimatter weapon|weapon]] against the Vatican. In response, CERN published a "Fact or Fiction?" page discussing the accuracy of the book's portrayal of the LHC, CERN, and particle physics in general.<ref>{{cite journal|date=2011|title=Angels and Demons|journal=New Scientist|volume=214|issue=2871|page=31|url=http://angelsanddemons.web.cern.ch |publisher=CERN |access-date=2 August 2015|bibcode=2012NewSc.214R..31T|last1=Taylor|first1=Allen|doi=10.1016/S0262-4079(12)61690-X}}</ref> The [[Angels & Demons (film)|movie version]] of the book has footage filmed on-site at one of the experiments at the LHC; the director, [[Ron Howard]], met with CERN experts in an effort to make the science in the story more accurate.<ref>{{cite web|author=Ceri Perkins|date=2 June 2008|title=ATLAS gets the Hollywood treatment|url=http://atlas-service-enews.web.cern.ch/atlas-service-enews/2007-8/news_07-8/news_angelphoto.php|website=ATLAS e-News|access-date=2 August 2015}}</ref>

The novel ''[[Flashforward (novel)|FlashForward]]'', by [[Robert J. Sawyer]], involves the search for the Higgs boson at the LHC. CERN published a "Science and Fiction" page interviewing Sawyer and physicists about the book and the [[FlashForward (2009 TV series)|TV series]] based on it.<ref>{{cite web |date=September 2009 |title=FlashForward |url=http://flashforward.web.cern.ch/flashforward/ |publisher=CERN |access-date=3 October 2009}}</ref>

== See also ==
{{Portal|Engineering|Physics|Science|Technology}}
* [[List of accelerators in particle physics]]
* Accelerator projects
** [[Circular Electron Positron Collider]]
** [[Compact Linear Collider]]
** [[Future Circular Collider]]
** [[International Linear Collider]]
** [[Very Large Hadron Collider]]

== References ==
{{reflist}}

== External links ==
{{Commons}}
* {{Official website}}
* [https://home.web.cern.ch/science/accelerators/large-hadron-collider Overview of the LHC at CERN's public webpage]
* [https://cerncourier.com/ CERN Courier magazine]
* [http://www.lhcportal.com/ LHC Portal] Web portal
* {{cite journal|editor1=Lyndon Evans |editor2=Philip Bryant |year=2008|title=LHC Machine |journal=[[Journal of Instrumentation]]|volume=3|issue=8|page=S08001
|doi=10.1088/1748-0221/3/08/S08001 |doi-access=free |bibcode=2008JInst...3S8001E |last1=Evans |first1=Lyndon |last2=Bryant |first2=Philip }} Full documentation for design and construction of the LHC and its six detectors (2008).

:'''Video'''
* {{YouTube|1sldBwpvGFg|CERN, how LHC works}}
* {{cite web|title=Petabytes at the LHC|url=http://www.sixtysymbols.com/videos/petabyte_LHC.htm|website=Sixty Symbols|publisher=[[Brady Haran]] for the [[University of Nottingham]]}}
* [https://cds.cern.ch/record/2021097 Animation of LHC in collision production mode (June 2015)]

:'''News'''
* [https://www.forbes.com/sites/chadorzel/2015/05/21/things-to-know-as-the-large-hadron-collider-breaks-energy-records/ Eight Things To Know As The Large Hadron Collider Breaks Energy Records]

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{{CERN}}
{{Standard model of physics}}
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