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It has a rest mass of 3096.9 MeV/ c² and a half life of only 8×10^{-21 s.}

It was discovered in 1974 independently by two research groups, one at the Stanford Linear Accelerator Center, headed by Burton Richter, and one at the Brookhaven National Laboratory, headed by Samuel Ting. These two scientists were both rewarded for their discovery with the 1976 Nobel Prize in PhysicsList of Nobel Prize laureates in Physics from 1901 to the present day. 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s 2000s 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s 2000s External links Official site (source for all citatio.

The significance of the discovery of the J/Ψ was that it confirmed the quark model of elementary particle physics, which says that protonFor alternative meanings see proton (disambiguation). Proton Classification Subatomic particle Fermion Hadron Baryon Nucleon Proton Properties Mass: 938 MeV/ c2 Electric Charge: 1. 6 × 10−19 C Spin: 1/2 In physics, the proton is a subatomic particles, neutronNeutron Classification Subatomic particle Fermion Hadron Baryon Nucleon Neutron Properties Mass: 940 MeV/ c 2 Electric Charge: 0 C Spin: 1/2 In physics, the neutron is a subatomic particle with no net electric charge and a mass of 940 MeV/ c 2 ( kg; verys and all the other baryonIn particle physics, the baryons are a family of subatomic particles including the proton and the neutron (collectively called nucleons), as well as a number of unstable, heavier particles (called hyperons). The term "baryon" is derived from the Greek bars are made up from a fundamental substance, namely the quark fields, which comes in 3 "colors" and 6 "flavors". At that time, 3 flavors were known (called up, down and strange) and the important point of the model was the claim that the flavors come in pairs: Up and down form the pair of the "first generation", and the "second generation" is a heavier and instable copy of the first. The "strange quark", was suspected to be behind the strange behavior of the kaonThe neutral Kaons represent symmetric and antisymmetric mixtures of the quark combinations down-antistrange and antidown-strange. The charged kaons are mesons which have a quark composition of up-antistrange for the positive kaon and antiup-strange for ths and took in the second generation the place corresponding to the down quark in first generation. For this to be true, one should be able to find particles, which indicate by the products into which they decay, that they contain a second generation quark, that corresponded to the up quark, and was given the name "charm quark" in the theory.

This all sounded nice, but in order to make it also convincing, the high energy theorists awaited with suspense whether their experimental collegues would find such a particle. The discovery of the J/Ψ was hence the triumph of the quark model as suggested before by Murray Gell-MannMurray Gell-Mann (born September 15, 1929) is an American physicist. Murray Gell-Mann received the 1969 Nobel Prize in physics for his work on the theory of elementary particles. He introduced the " eightfold way" as a means to coherently organize the gre and others.

The J/Ψ is the only elementary particle to have two letters assigned. The story behind is this: Richter and his coworkers observed the decay of an excited J/Ψ (just created in the SLAC particle accelerator) into the ground state J/Ψ, emitting two low-energy pions in the process, which left curved traces in their

Ting, at about the same time, assigned the name J to it (without as obvious reasons, though rumor has it, because his Chinese name Ting (丁) looks like a letter J in Chinese writing.)

As the discoveries were about simultaenous, and the scientific community considered it unjust to give one of the two discoverors priority, most subsequent publications refered to the particle as the "J/Ψ".

The name charmonium is occasionally used for the J/Ψ. This is by analogy with positronium, which also consists of a particle (a positron in the case of positronium) and its antiparticle.

Also, when refering to excited states of the J/Ψ (i.e. bound states of a charm quark and a charm antiquark with higher rest mass 3096.9 MeV, the mass in MeV is appended to the "J/Ψ" in parantheses.