Ratios of B and D meson decay constants with heavy quark symmetry

Abstract

SU(3) flavor symmetry allows the decay constants fDs and fDd as well as fBs and fBd to be equal. But due to SU(3) flavor symmetry breaking the ratios fBs/fBd and fDs/fDd are deviated from unity. We have estimated these ratios in the heavy quark effective theory and obtained fBs/fBd = 0·93, fDs/fDd = 0·94 and the double ratio (fBs/fBd)/(fDs/fDd) = 0·99.