The J/ψ (J/psi) meson /ˈdʒeɪ ˈsaɪ ˈmiːzɒn/ or psion ( J/psi ParticleThe J/ψ (J/psi) meson /ˈdʒeɪ ˈsaɪ ˈmiːzɒn/ or psion is a subatomic particle, a neutral pai meson consisting of a charm quark and a charm antiquark. These Pai Mesons formed by a bound state of a charm quark and a charm anti-quark are generally known as “charmonium”.
The J/ψ or J/psi Particle is the most common form of charmonium, due to its spin of 1 and its low rest mass. The J/ψ or J/psi Particle has a rest mass of 3.0969 GeV/c2, just above that of the η c (2.9836 GeV/c2), and a mean lifetime of 7.2×10−21 s. This lifetime of J/psi Particle was about a thousand times longer than expected.
The mass of Pai Meson or J/psi Particle is 274 times to the mass of electron.