Branching Fraction Measurements of B ->etac K Decays

Abstract

We study the decays B+ -> etac K+ and B0 -> etac K0, where the etac is reconstructed in the Ks K+ pi- and K+ K- pi0 decay modes. Results are based on a sample of 86 million BBbar pairs collected with the BaBar detector at the SLAC e+e- B Factory. We measure the branching fractions BR(B+ -> etac K+) = (1.34 +/- 0.09 +/- 0.13 +/- 0.41) x 10^{-3} and BR(B0 -> etac K0) = (1.18 +/- 0.16 +/- 0.13 +/- 0.37) x 10^{-3}, where the first error is statistical, the second is systematic, and the third reflects the etac branching fraction uncertainty. In addition, we search for B -> etac K events with etac -> 2(K+K-) and etac -> phi phi and determine the etac decay branching fraction ratios BR(etac -> 2(K+K-))/BR(etac -> K Kbar pi) = (2.3 +/- 0.7 +/- 0.6) x 10^{-2} and BR(etac -> phi phi)/BR(etac -> K Kbar pi) = (5.5 +/- 1.4 +/- 0.5) x 10^{-2}.