Observation of triple J-psi Meson Production
T he J/ψ meson (J/psi meson or psion) is a flavor-neutral meson about three times more massive than a proton. This particle consists of a charm and an anti-charm pair held together tightly via the strong force. It was discovered in two experiments unexpectedly in 1974, in the so-called ‘November Revolution’ of particle physics. This, in turn, led to the discovery of the charm quark, a heavier cousin of the up quark. It fetched the pioneers of the experiments — Burton Richter and Samuel Ting — the Physics Nobel prize in 1976, and, importantly, opened a new window in the field of high-energy physics. ATLAS, CMS and LHCb experiments have previously seen one or two J/ψ particles coming out of a single particle collision, but never before have they seen the simultaneous production of three J/ψ particles — until the new CMS analysis. The rarity of this process is reflected in the number of events found, which is a meager 5, out of almost 100 billion proton-proton interactions t...