ISSN - 00319007, EISSN - 10797114, Physical Review Letters, 2007, vol. 99, p. -
Measurements of branching fractions for bâ†KÏ€ and Bâ†Ï€Ï€ decays
We report measurements of branching fractions for Bâ†KÏ € and Bâ†Ï€Ï€ decays based on a data sample of 449Ã-106 BBÂ pairs collected at the Î¥(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. We also measure the ratios of partial widths for Bâ†KÏ€ decays, namely Rcâ‰2Î"(B+â†K+Ï€0) /Î"(B+â† K0Ï€+)=1.08Â±0. 06Â±0.08 and Rnâ‰Î"(B0â† K+Ï€-)/2Î"(B0â† K0Ï€0)=1. 08Â±0.08Â±0.08, where the first and the second errors are statistical and systematic, respectively. These ratios are sensitive to enhanced electroweak penguin contributions from new physics; the new measurements are, however, consistent with standard model expectations. © 2007 The American Physical Society.