Sign of theKL−KSMass Difference

Abstract

The sign of the (${K_L}^0-{K_S}^0$) mass difference has been measured by studying the time distribution of scattered neutral $K$ mesons, using $K^0\text{'}\mathrm{s}$ from the reaction $K^{+}+d\to K^0+p+p$. We obtain $m\left(K_L\right)>m\left(K_S\right)$.