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{{Short description|Type of quark}}
{{Redirect|Charm (physics)||Charm (disambiguation)#Science and technology}}
{{Infobox Particle
 |bgcolour        =
 |name            = Charm quark 
 |image           =[[FILE:Charm quark.svg|150px]]
 |caption         =
 |num_types       =
 |composition     = [[Elementary particle]]
 |statistics      = [[Fermionic]]
 |group           = [[Quark]]
 |generation      = Second
 |interaction = [[Strong interaction|strong]], [[Weak interaction|weak]], [[electromagnetic force]], [[gravity]]
 |particle        =
 |antiparticle    = Charm antiquark ({{SubatomicParticle|Charm antiquark}})
 |theorized       = [[Sheldon Lee Glashow|Sheldon Glashow]],<br> [[John Iliopoulos]],<br> [[Luciano Maiani]] (1970)
 |discovered      =  {{plainlist|
*[[Burton Richter]] ''et al.'' ([[SLAC]], 1974)
*[[Samuel C. C. Ting|Samuel Ting]] ''et al.'' ([[Brookhaven National Laboratory|BNL]], 1974)}}
 |symbol          = {{SubatomicParticle|Charm quark}}
 |mass            = {{val|1.275|+0.025|-0.035|ul=GeV/c2}}<ref name="PDG2018">
{{cite journal
 |author=M. Tanabashi et al. (Particle Data Group)
 |title=Review of Particle Physics
 |year= 2018
 |doi=10.1103/PhysRevD.98.030001
 |volume=98
 |issue=3
 |pages=030001
 |journal=Physical Review D
 |url=http://pdglive.lbl.gov/DataBlock.action?node=Q004M
 |doi-access=free
 |bibcode=2018PhRvD..98c0001T
 }}</ref>
 |decay_time      =
 |decay_particle  = [[Strange quark]] (~95%), [[down quark]] (~5%)<ref name="hyperphysics">
{{cite web
 |quote=The c quark has about 5% probability of decaying into a d quark instead of an s quark.
 |author=R. Nave
 |url=http://hyperphysics.phy-astr.gsu.edu/hbase/particles/qrkdec.html
 |title=Transformation of Quark Flavors by the Weak Interaction
 |access-date=2010-12-06
}}</ref><ref name="PDG2010_CKM">
{{cite journal
 |author=K. Nakamura ''et al.'' ([[Particle Data Group]])
 |year=2010
 |title=Review of Particles Physics: The CKM Quark-Mixing Matrix
 |url=http://pdg.lbl.gov/2010/reviews/rpp2010-rev-ckm-matrix.pdf
 |journal=[[Journal of Physics G]]
 |volume=37 |issue=75021 |page=150
 |doi=10.1088/0954-3899/37/7a/075021
|display-authors=etal 
 |bibcode=2010JPhG...37g5021N}}</ref>
 |electric_charge = +{{sfrac|2|3}} [[Elementary charge|''e'']]
 |color_charge    = Yes
 |spin            = {{sfrac|1|2}}
 |num_spin_states =
 |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 '''charm quark''', '''charmed quark''' or '''c quark''' (from its symbol, c) is the third most massive of all [[quark]]s, a type of [[elementary particle]]. Charm quarks are found in [[hadron]]s, which are [[subatomic particle]]s made of quarks. Examples of hadrons containing charm quarks include the [[J/ψ]] meson ({{SubatomicParticle|J/Psi}}), [[D meson]]s ({{SubatomicParticle|D}}), [[charmed Sigma baryon]]s ({{SubatomicParticle|charmed Sigma}}), and other charmed particles.

It, along with the [[strange quark]], is part of the [[generation (particle physics)|second generation]] of matter, and has an [[electric charge]] of +{{sfrac|2|3}}&nbsp;[[elementary charge|''e'']] and a [[Quark#Mass|bare mass]] of {{val|1.275|+0.025|-0.035|ul=GeV/c2}}.<ref name="PDG2018"/> Like all [[quark]]s, the charm quark is an [[elementary particle|elementary]] [[fermion]] with [[spin (physics)|spin]] [[spin-1/2|{{sfrac|1|2}}]], and experiences all four [[fundamental interaction]]s: [[gravitation]], [[electromagnetism]], [[weak interaction]]s, and [[strong interaction]]s. The [[antiparticle]] of the charm quark is the '''charm antiquark''' (sometimes called ''anticharm quark'' or simply ''anticharm''), which differs from it only in that some of its properties have [[additive inverse|equal magnitude but opposite sign]].

The existence of a fourth quark had been speculated by a number of authors around 1964 (for instance by [[James Bjorken]] and [[Sheldon Lee Glashow|Sheldon Glashow]]<ref>
{{cite journal
 |author=B.J. Bjorken, S.L. Glashow
 |year=1964
 |title=Elementary particles and SU(4)
 |journal=[[Physics Letters]]
 |volume=11 |pages=255–257
 |doi=10.1016/0031-9163(64)90433-0
|bibcode = 1964PhL....11..255B
 |issue=3 |last2=Glashow
 }}</ref>), but its prediction is usually credited to [[Sheldon Lee Glashow|Sheldon Glashow]], [[John Iliopoulos]] and [[Luciano Maiani]] in 1970 (see [[GIM mechanism]]).<ref>
{{cite journal
 |author=S.L. Glashow, J. Iliopoulos, L. Maiani
 |year=1970
 |title=Weak Interactions with Lepton–Hadron Symmetry
 |journal=[[Physical Review D]]
 |volume=2 |pages=1285–1292
 |doi=10.1103/PhysRevD.2.1285
|bibcode = 1970PhRvD...2.1285G
 |issue=7 |last2=Iliopoulos
 |last3=Maiani
 }}</ref> Glashow is quoted as saying, "We called our construct the 'charmed quark', for we were fascinated and pleased by the symmetry it brought to the subnuclear world."<ref>
{{cite book
 |author=M. Riordan
 |title=The Hunting of the Quark: A True Story of Modern Physics
 |page=[https://archive.org/details/huntingofquarktr00mich/page/210 210]
 |publisher=[[Simon & Schuster]]
 |year=1987
 |isbn=978-0-671-50466-3
 |url=https://archive.org/details/huntingofquarktr00mich/page/210
 }}</ref> The first charmed particle (a particle containing a charm quark) to be discovered was the [[J/ψ meson]]. It was discovered in 1974 by a team at the [[Stanford Linear Accelerator Center]] (SLAC), led by [[Burton Richter]],<ref>
{{cite journal
 |author=J.-E. Augustin
 |year=1974
 |title=Discovery of a Narrow Resonance in ''e''<sup>+</sup>''e''<sup>−</sup> Annihilation
 |journal=[[Physical Review Letters]]
 |volume=33 |issue=23 |page=1406
 |bibcode=1974PhRvL..33.1406A
 |doi=10.1103/PhysRevLett.33.1406
|display-authors=etal|doi-access=free
 }}</ref> and one at the [[Brookhaven National Laboratory]] (BNL), led by [[Samuel C. C. Ting|Samuel Ting]].<ref>
{{cite journal
 |author=J.J. Aubert
 |year=1974
 |title=Experimental Observation of a Heavy Particle ''J''
 |journal=[[Physical Review Letters]]
 |volume=33 |issue=23 |page=1404
 |bibcode=1974PhRvL..33.1404A
 |doi=10.1103/PhysRevLett.33.1404
|display-authors=etal|doi-access=free
 }}</ref>

The 1974 discovery of the {{SubatomicParticle|J/Psi}} (and thus the charm quark) ushered in a series of breakthroughs which are collectively known as the ''[[November Revolution (physics)|November Revolution]]''.

== Hadrons containing charm quarks ==
{{Main list|List of baryons|list of mesons}}

Some of the [[hadron]]s containing charm quarks include:
* [[D meson]]s contain a charm quark (or its [[antiparticle]]) and an [[up quark|up]] or [[down quark]].
* {{SubatomicParticle|Strange D}} mesons contain a charm quark and a [[strange quark]].
* There are many [[charmonium]] states, for example the {{SubatomicParticle|J/Psi}} particle. These consist of a charm quark and its antiparticle.
* [[Charmed baryon]]s have been observed, and are named in analogy with strange baryons (e.g. {{SubatomicParticle|Charmed Lambda+}}).

==See also==
*[[Quark model]]

== References ==
{{Reflist}}

==Further reading==
*{{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
}}

{{Particles}}
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[[Category:Quarks]]
[[Category:Elementary particles]]