Branching fractions and CP-violating asymmetries in radiative B decays to ηKγ

Abstract

We present measurements of the C P -violation parameters S and C for the radiative decay B 0 → η K 0 S γ ; for B → η K γ we also measure the branching fractions and for B + → η K + γ the time-integrated charge asymmetry A c h . The data, collected with the BABAR detector at the Stanford Linear Accelerator Center, represent 465 × 10 6 B ¯¯¯ B pairs produced in e + e − annihilation. The results are S = − 0.18 + 0.49 − 0.46 ± 0.12 , C = − 0.32 + 0.40 − 0.39 ± 0.07 , B ( B 0 → η K 0 γ ) = ( 7.1 + 2.1 − 2.0 ± 0.4 ) × 10 − 6 , B ( B + → η K + γ ) = ( 7.7 ± 1.0 ± 0.4 ) × 10 − 6 , and A c h = ( − 9.0 + 10.4 − 9.8 ± 1.4 ) × 10 − 2 . The first error quoted is statistical and the second systematic.