$\Delta \mathit S$ = 2 VIA MIXING
Allowed in second-order weak interactions, e.g. mixing.
 ${\mathit m}_{{{\mathit K}_L^0} }–{\mathit m}_{{{\mathit K}_S^0} }$ ($52.81$ $\pm0.09$) $\times 10^{8}$ $\hbar{}$ s${}^{-1}$
 ${\mathit m}_{{{\mathit K}_L^0} }–{\mathit m}_{{{\mathit K}_S^0} }$ ($3.484$ $\pm0.006$) $\times 10^{-12}$ MeV