Measurement of the direct $CP$ asymmetry in $\bar{B}\to X_{s+d}{\hat{I}}^3$ decays with a lepton tag

Abstract

We report the measurement of the direct $CP$ asymmetry in the radiative $\bar{B}\to X_{s+d}{\hat{I}}^3$ decay using a data sample of $(772\pm 11)\times 10^6$ $B\bar{B}$ pairs collected at the $\hat{I}\yen (4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. The $CP$ asymmetry is measured as a function of the photon energy threshold. For $E_{\hat{I}}^3\ge 2.1\mathrm{GeV}$, where $E_{\hat{I}}^3$ is the photon energy in the center-of-mass frame, we obtain ${\mathcal{A}}_{CP}(\bar{B}\to X_{s+d}{\hat{I}}^3)=(2.2\pm 3.9\pm 0.9)\%$, consistent with the Standard Model prediction.

Published at PRL