Search for directCPviolation inB→Kπdecays

We search for direct $\mathrm{CP}$ violation in flavor specific $\overrightarrow{B}K\pi$ decays by measuring the rate asymmetry between charge conjugate modes.The search is performed on a data sample of $11.1\times {10}^6$ $B\overline{B}$ events recorded on the ${\rm Y}\mathrm{}\left(4S\right)\mathrm{}$ resonance by the Belle experiment at KEKB. We measure $90\%$ confidence intervals in the partial rate asymmetry ${\mathcal{A}}_{\mathrm{CP}}$ of $-0.25<\mathrm{}{\mathcal{A}}_{\mathrm{CP}}{(K}^{\mp }{\pi }^{\pm })<\mathrm{}0.37,$ $-0.40<\mathrm{}{\mathcal{A}}_{\mathrm{CP}}{(K}^{\mp }{\pi }^0)<\mathrm{}0.36,$ and $-0.53<\mathrm{}{\mathcal{A}}_{\mathrm{CP}}{(K}^0{\pi }^{\mp })<\mathrm{}\mathrm{0.82.}\mathrm{}$ By combining the $K^{\mp }{\pi }^{\pm }$ and $K^{\mp }{\pi }^0$ final states, we conclude that $-0.22<\mathrm{}{\mathcal{A}}_{\mathrm{CP}}\left(K^{\mp }\right({\pi }^{\pm }+{\pi }^0\left)\right)<0.25\mathrm{}$ at the $90\%$ confidence level.