Measurement of the time-dependentCP-violating asymmetry inB0→KS0π0γdecays

Abstract

We present a measurement of the time-dependent CP-violating asymmetry in $B^0 \to K^{*}_0\gamma$ decays with $K^{*}_0\to K^{0}_s\pi^0$ based on 232 million $\Upsilon(4\mathrm{S})\to B\bar{B}$ decays collected with the BaBar detector at the PEP-II asymmetric-energy $e^{+}e^{-}$ collider at SLAC. In a sample containing $157\pm 16$ signal decays, we measure $S_{K^{*}_0\gamma} = -0.21 \pm 0.40 \pm 0.05$ and $C_{K^{*}_0\gamma}= -0.40 \pm 0.23 \pm 0.03$, where the first error is statistical and the second systematic. We also explore $B^0 \to K^{0}_s\pi^0\gamma$ decays with $1.1<m_{K^{0}_s\pi^0}<1.8$ GeV$/c^2$ and find $59\pm13$ signal events with $S_{K^{0}_s\pi^0} = 0.9 \pm 1.0 \pm 0.2$ and $C_{K^{0}_s\pi^0} = -1.0 \pm 0.5 \pm 0.2$.