n.
Any member of a family of subatomic particles composed of a quark and an antiquark (see antimatter ).
Mesons are sensitive to the strong force , have integral spin , and vary widely in mass . Though unstable, many mesons last a few billionths of a second, long enough to be observed with particle detectors. They are readily produced in the collisions of high-energy subatomic particles (e.g., in cosmic rays ).