An unstable meson produced either in an electrically charged form with a mass966 times that of an electron or in a neutral form with a mass974 times that of an electron as a result of a high-energy particle collision.

• K介子一种不稳定的介子，由于高能粒子碰撞，在带电结构中产生，其质量为一个电子的966倍；或在不带电的结构中产生，其质量为一个电子的974倍