This second-generation particle is the third-most-massive quark, with a mass of 1.27±0.02 GeV/c2 as measured in 2022, and a charge of +⁠2/3⁠ e. The existence of the charm quark was first predicted by James Bjorken and Sheldon Glashow in 1964,[1][2][3] and in 1970, Glashow, John Iliopoulos, and Luciano Maiani showed how its existence would account for experimental and theoretical discrepancies.

[4] In 1974, its existence was confirmed through the independent discoveries of the J/psi meson at Brookhaven National Laboratory and the Stanford Linear Accelerator Center.

According to Sheldon Glashow, the charm quark received its name because of the "symmetry it brought to the subnuclear world".

[5][6] Glashow also justified the name as "a magical device to avert evil", because adding the charm quark would prohibit unwanted and unseen decays in the three-quark theory at the time.

[19] They also suggested the charmed quark could provide a mechanism—the GIM mechanism—to facilitate the unification of the weak and electromagnetic forces.

[20] At the Conference on Experimental Meson Spectroscopy (EMS) in April 1974, Glashow delivered his paper titled "Charm: An Invention Awaits Discovery".

Glashow asserted because neutral currents were likely to exist, a fourth quark was "sorely needed" to explain the rarity of the decays of certain kaons.

In late May 1974, Robert Palmer and Nicholas P. Samios found an event generating a lambda baryon from their bubble chamber at Brookhaven National Laboratory.

[31] In 1974, Samuel C. C. Ting was searching for charmed particles at Brookhaven National Laboratory (BNL).

[35] At the Stanford Linear Accelerator Center (SLAC), Burton Richter's team performed experiments on 9–10 November 1974.

[42] Some other theorists, such as Richard Feynman, initially thought the new particle consisted of an up quark with a charm antiquark.

[43] On 21 November at the SLAC, SPEAR found a resonance of the J/psi particle at 3.7 GeV/c2 as Martin Breidenbach and Terence Goldman had predicted.

Glashow and Alvaro De Rujula also published a paper called "Is Bound Charm Found?

[45] Eventually, on 2 December 1974, Physical Review Letters (PRL) published the discovery papers of J and psi, by Ting[46] and Richter[47] respectively.

[45] Then, on 6 January 1975, PRL published nine theoretical papers on the J/psi particle; according to Michael Riordan, five of them "promoted the charm hypothesis and its variations".

[30] In 1976, Ting and Richter shared the Nobel Prize in Physics for their discovery "of a heavy elementary particle of the new kind".

[49][50] Frank Close wrote a Nature article titled "Iliopoulos won his bet" in the same year, saying the 18th ICHEP was "indeed dominated by that very discovery".

[51][38] In April 1975, E. G. Cazzoli et al., including Palmer and Samios, published their earlier ambiguous evidence for the charmed baryon.

[53] Starting from the fourth quarter of that year, physicists began to look for particles with a net, or "naked", charm.

[54] On 3 May 1976 at SLAC, Gerson Goldhaber and François Pierre identified a 1.87 GeV/c2 peak, which suggested the presence of a neutral charmed D meson according to Glashow's prediction.

[66][67] In the same year, physicists also conducted a direct search for Higgs boson decays into charm quarks using the ATLAS detector of the Large Hadron Collider.

[69] On 7 July 2022, the LHCb experiment announced they had found evidence of direct CP violation in the decay of the D0 meson into pions.

[75] Charmed baryons include Λc, Σc, Ξc, Ωc, with various charges and resonances.

[78] Hadron colliders produce particles that contain charm quarks at a higher cross section.