resonance, in particle physics, an extremely short-lived phenomenon associated with subatomic particles called hadrons that decay via the strong nuclear force. This force is so powerful that it allows resonances to exist only for the amount of time it takes light to cross each such “object.” A resonance occurs when the net energy of the colliding subatomic particles is just enough to produce its rest mass, which the strong force then causes to disintegrate within 10-23 second.