View source for Top quark

{{Short description|Type of quark}}
{{use dmy dates|date=February 2023}}
{{Infobox Particle
 |bgcolour    =
 |name        = Top quark
 |image       = Top antitop quark event.svg
 |image_size  = 250px
 |caption     = A collision event involving top quarks
 |num_types   = 
 |composition = [[elementary particle]]
 |statistics  = [[fermionic]]
 |group       = [[quark]]
 |generation  = third 
 |interaction = [[Strong interaction|strong]], [[Weak interaction|weak]], [[Electromagnetic interaction|electromagnetic]], [[gravity]]
 |particle    = 
 |antiparticle= top antiquark ({{SubatomicParticle|Top antiquark}})
 |theorized   = [[Makoto Kobayashi (physicist)|Makoto Kobayashi]] and [[Toshihide Maskawa]] (1973)
 |discovered  = [[Collider Detector at Fermilab|CDF]] and [[D0 experiment|DØ]] collaborations (1995)
 |symbol      = {{SubatomicParticle|Top quark}}
 |mass        = {{val|172.76|0.3|ul=GeV/c2}}<ref name=PDG2020/>
 |mean_lifetime   = {{val|5|e=-25|u=s}}
 |decay_particle  = {{nowrap|[[bottom quark]] (99.8%)}}<br/>{{nowrap|[[strange quark]] (0.17%)}}<br/>{{nowrap|[[down quark]] (0.007%)}}
 |electric_charge = +{{sfrac| 2 |3}} [[Elementary charge|''e'']]
 |color_charge    = yes
 |spin            = {{sfrac| 1 |2}}&nbsp;[[reduced Planck constant|''ħ'']]
 |topness         = 1
 |weak_isospin    = {{nowrap|[[Chirality (physics)|LH]]: +{{sfrac| 1 |2}}, [[Chirality (physics)|RH]]: 0}}
 |weak_hypercharge= {{nowrap|[[Chirality (physics)|LH]]: +{{sfrac| 1 |3}}, [[Chirality (physics)|RH]]: +{{sfrac| 4 |3}}}}
}} 
The '''top quark''', sometimes also referred to as the '''truth quark''', (symbol: t) is the most massive of all observed [[elementary particle]]s. It derives its mass from its coupling to the [[Higgs field]]. This coupling {{math|''y''}}{{sub|t}} is very close to unity; in the [[Standard Model]] of [[particle physics]], it is the largest (strongest) coupling at the scale of the weak interactions and above. The top quark was discovered in 1995 by the [[Collider Detector at Fermilab|CDF]]<ref name=CDF-1995/> and [[DØ experiment|DØ]]<ref name=D0-1995/> experiments at [[Fermilab]].

Like all other [[quark]]s, the top quark is a [[fermion]] with [[spin-1/2]] and participates in all four [[fundamental interaction]]s: [[gravitation]], [[electromagnetism]], [[weak interaction]]s, and [[strong interaction]]s. It has an [[electric charge]] of +{{sfrac| 2 |3}}&nbsp;[[elementary charge|''e'']]. It has a [[Quark#Mass|mass]] of {{val|172.76|0.3|ul=GeV/c2}},<ref name=PDG2020/> which is close to the [[rhenium]] atom mass.<ref name=Hypertextbook/>{{Verify source|date=December 2024}}<!-- 173.0 GeV/c^2 * 0.931494 u/GeV/c^2 = 185.723 u. --> The [[antiparticle]] of the top quark is the '''top antiquark''' (symbol: {{overline|t}}, sometimes called ''antitop quark'' or simply ''antitop''), which differs from it only in that some of its properties have [[charge conjugation|equal magnitude but opposite sign]].

The top quark interacts with [[gluons]] of the [[strong interaction]] and is typically produced in hadron colliders via this interaction. However, once produced, the top (or antitop) can decay only through the [[weak force]]. It decays to a [[W boson]] and either a [[bottom quark]] (most frequently), a [[strange quark]], or, on the rarest of occasions, a [[down quark]].{{efn|name=predominantly_decays_to_bottom}}

The Standard Model determines the top quark's [[mean lifetime]] to be roughly {{val|5|e=-25|u=s}}.<ref name=Quadt/> This is about a twentieth of the timescale for strong interactions,{{efn|name=exceptionally_fast_weak_interaction}} and therefore it does not [[Hadronization|form hadrons]], giving physicists a unique opportunity to study a "bare" quark (all other quarks [[Hadronization|hadronize]], meaning that they combine with other quarks to form [[hadron]]s and can only be observed as such).

Because the top quark is so massive, its properties allowed indirect determination of the mass of the [[Higgs boson]] (see ''{{slink||Mass and coupling to the Higgs boson}}'' below). As such, the top quark's properties are extensively studied as a means to discriminate between competing theories of new physics beyond the Standard Model. The top quark is the only quark that has been directly observed due to its decay time being shorter than the hadronization time.{{efn|name=exceptionally_fast_weak_interaction}}<ref>{{cite book |last1=Aubert |first1=Jean-Jacques |last2=Gastmans |first2=Raymond |last3=Gérard |first3=Jean-Marc |date=6 December 2012 |title=Particle Physics: Ideas and recent developments |publisher=Springer, Dordrecht |isbn=978-0-7923-6436-8 |pages=69 |url=https://books.google.com/books?id=46bnCAAAQBAJ&q=top+quark+has+been+observed+directly&pg=PA69 |access-date=11 June 2020}}</ref>

== History ==
In 1973, [[Makoto Kobayashi (physicist)|Makoto Kobayashi]] and [[Toshihide Maskawa]] predicted the existence of a third generation of quarks to explain observed [[CP violation]]s in [[kaon]] [[particle decay|decay]]. The names top and [[bottom quark|bottom]] were introduced by [[Haim Harari]] in 1975,<ref name=Harari/><ref name=Staley/> to match the names of the first generation of quarks ([[up quark|up]] and [[down quark|down]]) reflecting the fact that the two were the "up" and "down" component of a [[weak isospin]] [[Doublet (physics)|doublet]].<ref name=Perkins/><ref name=Close/>

The proposal of Kobayashi and Maskawa heavily relied on the [[GIM mechanism]] put forward by [[Sheldon Glashow]], [[John Iliopoulos]] and [[Luciano Maiani]],<ref name=Glashow/> which predicted the existence of the then still unobserved [[charm quark]]. (Direct evidence for the existence of quarks, including the other [[Generation (physics)|second generation]] quark, the [[strange quark]], was obtained in 1968; strange particles were discovered back in 1947.) When in [[November Revolution (physics)|November 1974]] teams at [[Brookhaven National Laboratory]] (BNL) and the [[Stanford Linear Accelerator Center]] (SLAC) simultaneously announced the discovery of the [[J/ψ meson]], it was soon after identified as a bound state of the missing charm quark with its antiquark. This discovery allowed the GIM mechanism to become part of the Standard Model.<ref name=Pickering/> With the acceptance of the GIM mechanism, Kobayashi and Maskawa's prediction also gained in credibility. Their case was further strengthened by the discovery of the [[tau (particle)|tau]] by [[Martin Lewis Perl]]'s team at SLAC between 1974 and 1978.<ref name=Perl/> The tau announced a third generation of [[leptons]], breaking the new [[symmetry (physics)|symmetry]] between leptons and quarks introduced by the GIM mechanism. Restoration of the symmetry implied the existence of a fifth and sixth quark.

It was in fact not long until a fifth quark, the bottom, was discovered by the [[E288 experiment]] team, led by [[Leon Lederman]] at [[Fermilab]] in 1977.<ref name=Fermilab/><ref name=Lederman/><ref name=Herb/> This strongly suggested that there must also be a sixth quark, the top, to complete the pair. It was known that this quark would be heavier than the bottom, requiring more energy to create in particle collisions, but the general expectation was that the sixth quark would soon be found. However, it took another 18&nbsp;years before the existence of the top was confirmed.<ref name=LissTipton1997/>

Early searches for the top quark at [[SLAC]] and [[DESY]] (in [[Hamburg]]) came up empty-handed. When, in the early 1980s, the [[Super Proton Synchrotron]] (SPS) at [[CERN]] discovered the [[W&nbsp;boson]] and the [[Z&nbsp;boson]], it was again felt that the discovery of the top was imminent. As the SPS gained competition from the [[Tevatron]] at Fermilab there was still no sign of the missing particle, and it was announced by the group at CERN that the top mass must be at least {{val|41|u=GeV/c2}}. After a race between CERN and Fermilab to discover the top, the accelerator at CERN reached its limits without creating a single top, pushing the lower bound on its mass up to {{val|77|u=GeV/c2}}.<ref name=LissTipton1997/>

The Tevatron was (until the start of [[Large Hadron Collider|LHC]] operation at [[CERN]] in 2009) the only hadron collider powerful enough to produce top quarks. In order to be able to confirm a future discovery, a second detector, the [[DZero experiment|DØ detector]], was added to the complex (in addition to the [[Collider Detector at Fermilab]] (CDF) already present). In October&nbsp;1992, the two groups found their first hint of the top, with a single creation event that appeared to contain the top. In the following years, more evidence was collected and on 22&nbsp;April 1994, the CDF group submitted their article presenting tentative evidence for the existence of a top quark with a mass of about {{val|175|u=GeV/c2}}. In the meantime, DØ had found no more evidence than the suggestive event in 1992. A year later, on 2&nbsp;March 1995, after having gathered more evidence and reanalyzed the DØ data (which had been searched for a much lighter top), the two groups jointly reported the discovery of the top at a mass of {{val|176|18|u=GeV/c2}}.<ref name=CDF-1995/><ref name=D0-1995/><ref name=LissTipton1997/>

In the years leading up to the top-quark discovery, it was realized that certain precision measurements of the electroweak vector boson masses and couplings are very sensitive to the value of the top-quark mass. These effects become much larger for higher values of the top mass and therefore could indirectly see the top quark even if it could not be directly detected in any experiment at the time. The largest effect from the top-quark mass was on the [[S and T parameters|T&nbsp;parameter]], and by 1994 the precision of these indirect measurements had led to a prediction of the top-quark mass to be between {{val|145|u=GeV/c2}} and {{val|185|u=GeV/c2}}.<ref name=LissTipton1997/> It is the development of techniques that ultimately allowed such precision calculations that led to [[Gerardus 't Hooft]] and [[Martinus Veltman]] winning the [[Nobel Prize]] in physics in 1999.<ref name=Nobel-1/><ref name=Nobel-2/>

== Properties ==
* At the final Tevatron energy of 1.96&nbsp;TeV, top–antitop pairs were produced with a [[Cross section (physics)|cross section]] of about 7&nbsp;[[picobarn]]s (pb).<ref name=D0-CDF/> The [[Standard Model]] prediction (at [[leading-order#Next-to-leading order|next-to-leading order]] with {{math|size=120%|''m''}}{{sub|t}} = {{val|175|u=GeV/c2}}) is 6.7–7.5&nbsp;[[picobarn|pb]].
* The W bosons from top quark decays carry polarization from the parent particle, hence pose themselves as a unique probe to top polarization.
* In the Standard Model, the top quark is predicted to have a spin quantum number of {{sfrac| 1 |2}} and electric charge {{sfrac|+| 2 |3}}. A first measurement of the top quark charge has been published, resulting in some confidence that the top quark charge is indeed&nbsp;{{sfrac|+| 2 |3}}.<ref name=Abazov2007a/>

== Production ==
Because top quarks are very massive, large amounts of energy are needed to create one. The only way to achieve such high energies is through high-energy collisions. These occur naturally in the Earth's upper atmosphere as [[cosmic ray]]s collide with particles in the air, or can be created in a [[particle accelerator]]. In 2011, after the [[Tevatron]] ceased operations, the [[Large Hadron Collider]] at [[CERN]] became the only accelerator that generates a beam of sufficient energy to produce top quarks, with a [[center-of-mass frame|center-of-mass energy]] of 7&nbsp;TeV. There are multiple processes that can lead to the production of top quarks, but they can be conceptually divided in two categories: top-pair production, and single-top production.

=== Top-quark pairs ===
{{Multiple image
| align = 
| direction = 
| background color = white
| image1 = Ttbar production via gg fusion.png
| width1=187
| caption1 = gluon–gluon fusion
| image2 = Ttbar production (t channel).png
| width2=187
| caption2 = t-channel
| image3 = Ttbar production via qqbar annihilation.png
| width3=187
| caption3 = quark–antiquark annihilation
}}
The most common is [[pair production|production of a top–antitop pair]] via [[strong interaction]]s. In a collision, a highly energetic [[gluon]] is created, which subsequently decays into a top and antitop. This process was responsible for the majority of the top events at Tevatron and was the process observed when the top was first discovered in 1995.<ref name=D0-2009/> It is also possible to produce pairs of top–antitop through the decay of an intermediate [[photon]] or [[Z-boson]]. However, these processes are predicted to be much rarer and have a virtually identical experimental signature in a [[hadron collider]] like Tevatron.

=== Single top quarks ===
{{Multiple image
| align = 
| direction = 
| background color = white
| image1 = Single-top production (s channel).png
| width1=179
| caption1 = s-channel
| image2 = Single-top production (t-channel).png
| width2=195
| caption2 = t-channel
| image3 = Single top production (tW channel).png
| width3=187
| caption3 = tW channel
}}

The production of single top quarks via [[weak interaction]] is a distinctly different process. This can happen in several ways (called channels): Either an intermediate [[W-boson]] decays into a top and antibottom quarks ("s-channel") or a bottom quark (probably created in a pair through the decay of a gluon) transforms to a top quark by exchanging a W&nbsp;boson with an up or down quark ("t-channel"). A single top quark can also be produced in association with a W&nbsp;boson, requiring an initial-state bottom quark ("tW-channel"). The first evidence for these processes was published by the DØ collaboration in December&nbsp;2006,<ref name=Abazov2007b/> and in March&nbsp;2009 the CDF<ref name=Aaltonen2009/> and DØ<ref name=D0-2009/> collaborations released twin articles with the definitive observation of these processes. The main significance of measuring these production processes is that their frequency is directly proportional to the {{math|{{!}}''V''<sub>tb</sub>{{!}}<sup>2</sup>}}&nbsp;component of the [[CKM matrix]].

== Decay ==
[[File:Ttbar decay channels.png|alt=ttbar-decay final states|thumb|upright=1.5|All possible final states of the decay of a top-quark pair]]
The only known way the top quark can decay is through the [[weak interaction]], producing a [[W and Z bosons|W&nbsp;boson]] and a [[bottom quark]].{{efn|
name=predominantly_decays_to_bottom|
The overwhelming majority of top&nbsp;quark decays produce a [[bottom quark]], whose mass is closest to the top's. On very rare occasions it may decay into a [[strange quark]]; ''almost'' never a [[down quark]].
}}
Because of its enormous [[mass]], the top quark is extremely short-lived, with a predicted lifetime of only {{val |5|e=-25|u=s}}.<ref name=Quadt/> As a result, top quarks do not have time before they decay to [[hadronization|form hadrons]] as other quarks do.{{efn|
name=exceptionally_fast_weak_interaction|
Top quark decay is an exceptional example of a [[weak interaction|weak process]] that is faster than a [[strong interaction]].
}}
The absence of a hadron surrounding the top quark provides physicists with the unique opportunity to study the behavior of a "bare" quark.

In particular, it is possible to directly determine the [[branching ratio]]:

<math display="block">\operatorname{B}\left(\ \mathrm{t} \to W^{+}\ \mathrm{b}\ \right) \equiv \frac{ \operatorname\Gamma\left(\ \mathrm{t} \to W^{+}\ \mathrm{b}\ \right) }{\ \sum_{ q\ =\ \mathrm{b, s, d} } \operatorname\Gamma\left(\ \mathrm{t} \to W^{+}\ q\ \right)\ } ~.</math>

The best current determination of this ratio is {{val|0.957|0.034}}.<ref name="PDG2020Quarks"/> Since this ratio is equal to {{math|{{!}}''V''<sub>tb</sub>{{!}}<sup>2</sup>}} according to the [[Standard Model]], this gives another way of determining the CKM element&nbsp;{{math|size=120%|{{!}}''V''<sub>tb</sub>{{!}}}}, or in combination with the determination of {{math|{{!}}''V''<sub>tb</sub>{{!}}}} from single top production provides tests for the assumption that the CKM matrix is unitary.<ref name=Abazov2008/>

The Standard Model also allows more exotic decays, but only at one loop level, meaning that they are extremely rare. In particular, it is conceivable that a top quark might decay into another up-type quark (an up or a charm) by emitting a photon or a Z-boson.<ref name=Chekanov2003/> However, searches for these exotic decay modes have produced no evidence that they occur, in accordance with expectations of the Standard Model. The branching ratios for these decays have been determined to be less than 1.8 in 10000 for photonic decay and less than 5 in 10000 for Z&nbsp;boson decay at 95% [[confidence level|confidence]].<ref name=PDG2020Quarks/>

== Mass and coupling to the Higgs boson ==
The Standard Model generates fermion masses through their couplings to the [[Higgs boson]].  This Higgs boson acts as a field that fills space. Fermions interact with this field in proportion to their individual coupling constants {{math|''y''{{sub|''i''}}}}, which generates mass. A low-mass particle, such as the [[electron]] has a minuscule coupling {{nowrap|1={{math|''y''}}{{sub|electron}} = {{val|2|e=-6}}}}, while the top quark has the largest coupling to the Higgs, {{nowrap|{{math|''y''}}{{sub|t}} ≈ 1}}.

In the Standard Model, all of the quark and lepton Higgs–Yukawa couplings are small compared to the top-quark Yukawa coupling. This hierarchy in the fermion masses remains a profound and open problem in theoretical physics. Higgs–Yukawa couplings are not fixed constants of nature, as their values vary slowly as the energy scale (distance scale) at which they are measured. These dynamics of Higgs–Yukawa couplings, called "running coupling constants", are due to a quantum effect called the [[renormalization group]].

The Higgs–Yukawa couplings of the up, down, charm, strange and bottom quarks are hypothesized to have small values at the extremely high energy scale of grand unification, {{val|e=15|u=GeV}}. They increase in value at lower energy scales, at which the quark masses are generated by the Higgs. The slight growth is due to corrections from the [[Quantum chromodynamics|QCD]] coupling. The corrections from the Yukawa couplings are negligible for the lower-mass quarks.

One of the prevailing views in particle physics is that the size of the top-quark Higgs–Yukawa coupling is determined by a unique nonlinear property of the [[renormalization group]] equation that describes the ''running'' of the large Higgs–Yukawa coupling of the top quark. If a quark Higgs–Yukawa coupling has a large value at very high energies, its Yukawa corrections will evolve downward in mass scale and cancel against the QCD corrections. This is known as a (quasi-) [[infrared fixed point]], which was first predicted by B. Pendleton and G.G. Ross,<ref name=PendletonRoss/> and by [[Christopher T. Hill]],<ref name=Hill1981/> No matter what the initial starting value of the coupling is, if sufficiently large, it will reach this fixed-point value. The corresponding quark mass is then predicted.

The top-quark Yukawa coupling lies very near the [[infrared fixed point]] of the Standard Model. The renormalization group equation is:

<math display="block">\mu\ \frac{\ \partial}{\partial\mu}\ y_\mathrm{t} \approx \frac{\ y_\text{t}\ }{16\ \pi^2}\left(\frac{\ 9\ }{2}y_\mathrm{t}^2 - 8 g_3^2- \frac{\ 9\ }{4}g_2^2 - \frac{\ 17\ }{20} g_1^2 \right)\ ,</math>

where {{mvar|g}}{{sub|3}} is the color gauge coupling, {{mvar|g}}{{sub|2}} is the weak isospin gauge coupling, and {{mvar|g}}{{sub|1}} is the weak hypercharge gauge coupling. This equation describes how the Yukawa coupling changes with energy scale&nbsp;{{mvar|μ}}. Solutions to this equation for large initial values {{mvar|y}}{{sub|t}} cause the right-hand side of the equation to quickly approach zero, locking {{mvar|y}}{{sub|t}} to the QCD coupling {{mvar|g}}{{sub|3}}.

The value of the top quark fixed point is fairly precisely determined in the Standard Model, leading to a top-quark mass of 220&nbsp;GeV. This is about 25% larger than the observed top mass and may be hinting at new physics at higher energy scales.

The quasi-infrared fixed point subsequently became the basis of [[top quark condensation]] and [[topcolor]] theories of electroweak symmetry breaking, in which the Higgs boson is composed of a pair of top and antitop quarks. The predicted top-quark mass comes into improved agreement with the fixed point if there are additional Higgs scalars beyond the standard model and therefore it may be hinting at a rich spectroscopy of new Higgs fields at energy scales that can be probed with the LHC and its upgrades.<ref name=Hill2019a/><ref name=Hill2019b/>

== See also ==
* [[CDF experiment]]
* [[Quark model]]
* [[Top quark condensate]]
* [[Topcolor]]
* [[Topness]]

== Footnotes ==
{{notelist}}

== References ==
{{reflist|25em|refs=

<ref name=Abazov2007a>
{{cite journal
 |first1=V.M.  |last1=Abazov
 |display-authors=etal
 |collaboration=[[DØ Collaboration]]
 |year=2007
 |title=Experimental discrimination between charge 2''e''/3 top quark and charge 4''e''/3 exotic quark production scenarios
 |journal=[[Physical Review Letters]]
 |volume=98  |issue=4  |page=041801
 |doi=10.1103/PhysRevLett.98.041801  |arxiv=hep-ex/0608044  |pmid=17358756
 |bibcode=2007PhRvL..98d1801A  |hdl=10211.3/194390  |s2cid=1147194
}}
</ref>

<ref name=Abazov2007b>
{{cite journal
 |first1=V.M.  |last1=Abazov
 |display-authors=etal
 |collaboration=[[DØ Collaboration]]
 |year=2007
 |title=Evidence for production of single top quarks and first direct measurement of {{!}}{{mvar|V}}<sub>tb</sub>{{!}}
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 |doi=10.1103/PhysRevLett.98.181802  |arxiv=hep-ex/0612052 |s2cid=14937909
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}}
</ref>

<ref name=Aaltonen2009>
{{cite journal
 |first1=T.  |last1=Aaltonen
 |display-authors=etal
 |collaboration=[[CDF Collaboration]]
 |year=2009
 |title=First observation of electroweak single top quark production
 |journal=[[Physical Review Letters]]
 |volume=103  |issue=9  |page=092002
 |doi=10.1103/PhysRevLett.103.092002  |pmid=19792788  |arxiv=0903.0885
 |bibcode=2009PhRvL.103i2002A  |hdl=1721.1/52314  |s2cid=8029289
}}
</ref>

<ref name=Abazov2008>
{{cite journal
 |first1=V.M.  |last1=Abazov
 |display-authors=etal
 |collaboration=[[DØ Collaboration]]
 |year=2008
 |title=Simultaneous measurement of the ratio ''B''(t&nbsp;→&nbsp;Wb)/''B''(t&nbsp;→&nbsp;Wq) and the top-quark pair production cross section with the DØ detector at {{mvar|{{sqrt|s}}}}&nbsp;=&nbsp;1.96&nbsp;TeV
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}}
</ref>

<ref name=CDF-1995>
{{cite journal
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}}
</ref>

<ref name=Chekanov2003>
{{cite journal
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 |collaboration=[[ZEUS Collaboration]] 
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 |title=Search for single-top production in e-p collisions at HERA
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}}
</ref>

<ref name=Close>
{{cite book
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 |year=2006
 |title=The New Cosmic Onion
 |page=133
 |publisher=[[CRC Press]]
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}}
</ref>

<ref name=D0-1995>
{{cite journal
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</ref>

<ref name=D0-2009>
{{cite journal
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 |collaboration=[[DØ Collaboration]]
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 |title=Observation of Single Top Quark Production
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 |volume=103 |issue=9 |pages=092001
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 |arxiv=0903.0850 |bibcode=2009PhRvL.103i2001A |hdl=10211.3/194327  |s2cid=14919683
}}
</ref>

<ref name=D0-CDF>
{{cite conference
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|arxiv=hep-ex/0212027
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</ref>

<ref name=Fermilab>
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}}
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<ref name=Glashow>
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</ref>

<ref name=Harari>
{{cite journal
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}}
</ref>

<ref name=Herb>
{{cite journal
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</ref>

<ref name=Hill1981>
{{cite journal
 |first1=Christopher T.  |last1=Hill
 |year=1981
 |title=Quark and lepton masses from renormalization group fixed points
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}} <!-- end "refs=" -->

== Further reading ==
* {{cite arXiv
 |date=June 2005
 |title=Top Quark Production and Properties at the Tevatron
 |eprint=hep-ex/0506005
 |author1=Frank Fiedler
 |author2=for the D0
 |author3=CDF Collaborations
}}
* {{cite web
 |author=R. Nave
 |title=Quarks
 |url=http://hyperphysics.phy-astr.gsu.edu/hbase/Particles/quark.html
 |work=[[HyperPhysics]]
 |publisher=[[Georgia State University]], Department of Physics and Astronomy
 |access-date=2008-06-29
}}
* {{cite book
 |author=A. Pickering
 |title=Constructing Quarks
 |pages=114–125
 |publisher=[[University of Chicago Press]]
 |year=1984
 |isbn=978-0-226-66799-7
}}

== External links ==
* {{cite web |title=Script to retrieve "top quark" on arxiv.org |url=http://xstructure.inr.ac.ru/x-bin/theme3.py?level=2&index1=234702 |url-status=dead |access-date=2023-02-19 |archive-date=16 January 2022 |archive-url=https://web.archive.org/web/20220116145702/http://xstructure.inr.ac.ru/x-bin/theme3.py?level=2&index1=234702 }}
* {{cite web |title=Tevatron Electroweak Working Group |website=[[Fermilab]]  |url=http://tevewwg.fnal.gov/top/ }}
* {{cite web |title=Top quark information |website=[[Fermilab]] |url=http://www.fnal.gov/pub/inquiring/physics/discoveries/top_quark.html }}
* {{cite web |title=CDF and DZero collaborations' top quark discovery  |type=discovery logbook pages |magazine=[[Symmetry Magazine]] |url=http://www.symmetrymag.org/cms/?pid=1000085 |url-status=dead <!-- presumed --> |archive-url=https://web.archive.org/web/20061002195520/http://www.symmetrymag.org/cms/?pid=1000085 |archive-date=2006-10-02 }}
* {{cite magazine |title=article on the discovery of the top quark |magazine=[[Scientific American]] |url=http://web.hep.uiuc.edu/home/tml/SciAmTop.pdf }}
* {{cite web |title=Top quark analysis results from DØ Collaboration |type=public homepage |website=[[Fermilab]] |url=http://www-d0.fnal.gov/Run2Physics/top/top_public_web_pages/top_public.html}}
* {{cite web |title=Top quark analysis results from CDF Collaboration |website=[[Fermilab]] |url=http://www-cdf.fnal.gov/physics/new/top/top.html }}
* {{cite magazine |title=article about the 1994 top quark discovery |magazine=[[Harvard Magazine]] |url=http://www.agwright.com/writing/articles/hm_quark.htm |archive-url=https://web.archive.org/web/20060508182322/http://www.agwright.com/writing/articles/hm_quark.htm |archive-date=8 May 2006 }}
* {{cite web |year=1999 |title=Nobel Prize in Physics |url=http://nobelprize.org/physics/laureates/1999/ }}

{{Particles}}
{{Authority control}}

{{DEFAULTSORT:Top Quark}}
[[Category:Elementary particles]]
[[Category:Quarks]]
[[Category:Standard Model]]