J/psi meson

Subatomic particle made of a charm quark and antiquark

The J/ψ (J/psi) meson 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 antiquark 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.

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