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 $S = -0.18^{ +0.49}_{ -0.46} \pm 0.12$, $C = -0.32^{ +0.40}_{ -0.39} \pm 0.07$, BF(B0 -> eta K0 gamma) = $(7.1^{ +2.1}_{ -2.0} \pm 0.4) \times 10^{ -6}$, BF(B+ -> eta K+ gamma) = $(7.7+-1.0 \pm 0.4) \times 10^{ -6}$, and Ach = $(-9.0^{ +10.4}_{ -9.8} \pm 1.4) \times 10^{ -2}$. The first error quoted is statistical and the second systematic.
Categories: hep-ex