Suppression of flavor symmetry breaking in B decay sum rules

While flavor symmetries are useful for studying hadronic B decays, symmetry relations for amplitudes and decay rates are usually violated by first order symmetry breaking corrections. We point out two cases in which first order symmetry breaking is suppressed by a small ratio of amplitudes: (1) An isospin sum rule for four B -> K pi decays, where isospin breaking is shown to be negligible. (2) An SU(3) sum rule for pairs of B -> K pi and B -> K eta(8), generalized to pairs of B -> K pi, B -> K eta and B -> K eta'. (c) 2006 Elsevier B.V. All rights reserved.