Suppression of flavor symmetry breaking in B decay sum rules

Abstract 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 π decays, where isospin breaking is shown to be negligible. (2) An SU ( 3 ) sum rule for pairs of B → K π and B → K η 8 , generalized to pairs of B → K π , B → K η and B → K η ′ .