Branching Fractions and CP-Violating Asymmetries in Radiative B Decays to eta K gamma

Abstract

We present measurements of the CP-violation parameters S and C for the radiative decay B0 -> eta K0s gamma; for B -> eta K gamma we also measure the branching fractions and for B+ -> eta K+ gamma the time-integrated charge asymmetry Ach. The data, collected with the BaBar detector at the Stanford Linear Accelerator Center, represent $465\times 10^6$ BBbar pairs produced in $e^{+}{e}^{-}$ annihilation. The results are $S=-0.18_{-0.46}^{+0.49}\pm 0.12$, $C=-0.32_{-0.39}^{+0.40}\pm 0.07$, BF(B0 -> eta K0 gamma) = $(7.1_{-2.0}^{+2.1}\pm 0.4)\times 10^{-6}$, BF(B+ -> eta K+ gamma) = $(7.7+-1.0\pm 0.4)\times 10^{-6}$, and Ach = $(-9.0_{-9.8}^{+10.4}\pm 1.4)\times 10^{-2}$. The first error quoted is statistical and the second systematic.

7 pages, 4 postscript figures, submitted to Phys. Rev. Letters