Time-Dependent {\boldmath $CP$}-Violating Asymmetry in $B^0\to {\rho }^0\gamma$ Decays

Abstract

We report the first measurement of CP-violation parameters in $B^0\to {\rho }^0\gamma$ decays based on a data sample of $657\times 10^{6}B\bar{B}$ pairs collected with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. The flavor of the $B$ meson is identified from the decay products of the accompanying $B$ meson. We obtain the time-dependent and direct CP-violating parameters, $\cals_{\rhozγ} = -0.83\pm 0.65(stat)\pm 0.18(syst)$ and $\cala_{\rhozγ} = -0.44\pm 0.49(stat)\pm 0.14(syst)$, respectively.

8 pages, 2 figures, published in PRL