Measurements of branching fractions and time-dependent CP-violating asymmetries in B→η′K decays

We present measurements of the B→η′K branching fractions; for B+→η′K+ we measure also the time-integrated charge asymmetry Ach, and for B0→η′KS0 the time-dependent CP-violation parameters S and C. The data sample corresponds to 232×106 BB̄ pairs produced by e+e- annihilation at the Υ(4S). The results are B(B→η′K+)= (68.9±2.0±3.2)×10-6, B(B0→η′K0)=(67. 4±3.3±3.2)×10-6, Ach=0.033±0.028±0.005, S=0.30±0.14±0.02, and C=-0.21±0.10±0.02, where the first error quoted is statistical and the second is systematic.