The charm quark, charmed quark or c quark (from its symbol, c) is the third-most massive of all

quark A quark () is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. All commonly o ...

s, a type of

elementary particle In particle physics, an elementary particle or fundamental particle is a subatomic particle that is not composed of other particles. Particles currently thought to be elementary include electrons, the fundamental fermions ( quarks, leptons, an ...

. Charm quarks are found in

hadron In particle physics, a hadron (; grc, ἁδρός, hadrós; "stout, thick") is a composite subatomic particle made of two or more quarks held together by the strong interaction. They are analogous to molecules that are held together by the ele ...

s, which are

subatomic particle In physical sciences, a subatomic particle is a particle that composes an atom. According to the Standard Model of particle physics, a subatomic particle can be either a composite particle, which is composed of other particles (for example, a pr ...

s made of quarks. Examples of hadrons containing charm quarks include the J/ψ meson (),

D meson The D mesons are the lightest particle containing charm quarks. They are often studied to gain knowledge on the weak interaction. The strange D mesons (Ds) were called "F mesons" prior to 1986. Overview The D mesons were discove ...

s (),

charmed Sigma baryon ''Charmed'' is an American fantasy drama television series created by Constance M. Burge and produced by Aaron Spelling and his production company Spelling Television, with Brad Kern serving as showrunner. The series was originally broadcas ...

s (), and other charmed particles. It, along with the strange quark, is part of the second generation of matter, and has an

electric charge Electric charge is the physical property of matter that causes charged matter to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative'' (commonly carried by protons and electrons respe ...

of + ''e'' and a

bare mass In quantum field theory, specifically the theory of renormalization, the bare mass of an elementary particle is the limit of its mass as the scale of distance approaches zero or, equivalently, as the energy of a particle collision approaches infin ...

of . Like all

s, the charm quark is an

elementary Elementary may refer to: Arts, entertainment, and media Music * ''Elementary'' (Cindy Morgan album), 2001 * ''Elementary'' (The End album), 2007 * ''Elementary'', a Melvin "Wah-Wah Watson" Ragin album, 1977 Other uses in arts, entertainment, a ...

fermion In particle physics, a fermion is a particle that follows Fermi–Dirac statistics. Generally, it has a half-odd-integer spin: spin , spin , etc. In addition, these particles obey the Pauli exclusion principle. Fermions include all quarks an ...

with spin , and experiences all four

fundamental interaction In physics, the fundamental interactions, also known as fundamental forces, are the interactions that do not appear to be reducible to more basic interactions. There are four fundamental interactions known to exist: the gravitational and electrom ...

gravitation In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stron ...

electromagnetism In physics, electromagnetism is an interaction that occurs between particles with electric charge. It is the second-strongest of the four fundamental interactions, after the strong force, and it is the dominant force in the interactions of a ...

weak interaction In nuclear physics and particle physics, the weak interaction, which is also often called the weak force or weak nuclear force, is one of the four known fundamental interactions, with the others being electromagnetism, the strong interaction, ...

s, and

strong interaction The strong interaction or strong force is a fundamental interaction that confines quarks into proton, neutron, and other hadron particles. The strong interaction also binds neutrons and protons to create atomic nuclei, where it is called the n ...

s. The

antiparticle In particle physics, every type of particle is associated with an antiparticle with the same mass but with opposite physical charges (such as electric charge). For example, the antiparticle of the electron is the positron (also known as an antie ...

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 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 James Daniel "BJ" Bjorken (born 1934) is an American theoretical physicist. He was a Putnam Fellow in 1954, received a BS in physics from MIT in 1956, and obtained his PhD from Stanford University in 1959. He was a visiting scholar at the Inst ...

and

Sheldon Glashow Sheldon Lee Glashow (, ; born December 5, 1932) is a Nobel Prize-winning American theoretical physicist. He is the Metcalf Professor of Mathematics and Physics at Boston University and Eugene Higgins Professor of Physics, Emeritus, at Harvard U ...

), but its prediction is usually credited to

John Iliopoulos John (Jean) Iliopoulos (Greek: Ιωάννης Ηλιόπουλος; 1940, Kalamata, Greece) is a Greek physicist. He is the first person to present the Standard Model of particle physics in a single report. He is best known for his prediction of ...

and

Luciano Maiani Luciano Maiani (born 16 July 1941, in Rome) is a Sammarinese physicist best known for his prediction of the charm quark with Sheldon Glashow and John Iliopoulos (the " GIM mechanism"). Academic history In 1964 Luciano Maiani received his degree ...

in 1970 (see

GIM mechanism In particle physics, the GIM mechanism (or Glashow–Iliopoulos–Maiani mechanism) is the mechanism through which flavour-changing neutral currents (FCNCs) are suppressed in loop diagrams. It also explains why weak interactions that change strang ...

). 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." 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 National Accelerator Laboratory, originally named the Stanford Linear Accelerator Center, is a United States Department of Energy National Laboratory operated by Stanford University under the programmatic direction of the U.S. Departme ...

(SLAC), led by

Burton Richter Burton Richter (March 22, 1931 – July 18, 2018) was an American physicist. He led the Stanford Linear Accelerator Center (SLAC) team which co-discovered the J/ψ meson in 1974, alongside the Brookhaven National Laboratory (BNL) team led by S ...

, and one at the

Brookhaven National Laboratory Brookhaven National Laboratory (BNL) is a United States Department of Energy national laboratory located in Upton, Long Island, and was formally established in 1947 at the site of Camp Upton, a former U.S. Army base and Japanese internment c ...

(BNL), led by Samuel Ting. The 1974 discovery of the (and thus the charm quark) ushered in a series of breakthroughs which are collectively known as the '' November Revolution''.

Hadrons containing charm quarks

Some of the

s containing charm quarks include: *

s contain a charm quark (or its

) and an up or

down quark The down quark or d quark (symbol: d) is the second-lightest of all quarks, a type of elementary particle, and a major constituent of matter. Together with the up quark, it forms the neutrons (one up quark, two down quarks) and protons (two up ...

. * mesons contain a charm quark and a strange quark. * There are many

charmonium In particle physics, quarkonium (from quark and -onium, pl. quarkonia) is a flavorless meson whose constituents are a heavy quark and its own antiquark, making it both a neutral particle and its own antiparticle. Light quarks Light quarks ( up ...

states, for example the particle. These consist of a charm quark and its antiparticle. * Charmed baryons have been observed, and are named in analogy with strange baryons (e.g. ).

Hadrons containing charm quarks

See also

References

Further reading