Precise determinations of the decay constants of B and D mesons

Abstract

Recently we studied the B, Bs, D and Ds meson decay constants using various treatments for the heavy quark. For B mesons, we determined fB, fBs , and fBs/ fB with NRQCD bottom quarks. We then combined the ratio fBs/ fB and another very precise determination from HPQCD for fBs using heavy HISQ quarks, and extracted fB with 2% total errors. We also calculated fD, fDs , and fDs/ fD using HISQ charm quarks. Here we review our results and briefly discuss their implications for the determination of the CKM matrix elements |Vcd| and |Vcs|.