K10−K20Mass Difference

A measurement of the magnitude of the ${K_1}^0-{K_2}^0$ mass difference yields $\frac{(1.5\mathrm{}\pm 0.2)\hslash }{{\tau }_1{c}^2}$. The method employed consisted of measuring the time dependence of the ${\overline{K}}^0$ intensity, in a beam which was initially in a pure $K^0$ state. The ${\overline{K}}^0$ intensity was measured by observing nuclear interactions. The $K^0$ mesons were produced by the charge exchange of $K^{+}$ mesons of 800-MeV/c momentum.