The J/ψ (J/psi) meson / ˈ dʒ eɪ ˈ s aɪ ˈ m iː z ɒ n / is a subatomic particle, a flavor -neutral meson consisting of a charm quark and a charm antiquark. Mesons formed by a bound state of a charm quark and a charm anti-quark are generally known as " charmonium " or psions. The J/ψ is the most common form of charmonium, due to its spin of 1 and its low rest mass. The J/ψ has a rest mass of 3.0969 GeV/ c, just above that of the η c (2.9836 GeV/ c), and a mean lifetime of 7.2 × 10 s. This lifetime was about a thousand times longer than expected.