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 B-0 --> eta K-S(0)gamma; for B --> eta K gamma we also measure the branching fractions and for B+ --> K+gamma the time-integrated charge asymmetry A(ch). The data, collected with the BABAR detector at the Stanford Linear Accelerator Center, represent 465 x 10(6) B (B) over bar pairs produced in e(+)e(-) annihilation. The results are S = -0.18(-0.46)(+0.49) +/- 0.12, C = -0.32(-0.39)(+0.40) +/- 0.07, B(B-0 --> eta K-0 gamma) = (7.1(-2.0)(+2.1) +/- 0.4) x 10(-6), B(B+ --> eta K+gamma) = (7.7 +/- 1.0 +/- 0.4) x 10(-6), and A(ch) = (-9.0(-9.8)(+10.4)) x 10(-2). The first error quoted is statistical and the second systematic.