Measurement of the branching ratioΓ(KL→π+π−)Γ(KL→all)

We have measured the branching ratio $\frac{\Gamma (K_L\to {\pi }^{+}{\pi }^{-})}{\Gamma (K_L\to \mathrm{all})}$ to be (2.01 ± 0.09) × ${10}^{-3\mathrm{}}$. This value is in good agreement with other recent determinations of this branching ratio and yields a value for the $\mathrm{CP}$-violating parameter $\left|{\eta }_{+-}\right|$ of (2.25 ± 0.05) × ${10}^{-3\mathrm{}}$.