f_B and f_Bs with maximally twisted Wilson fermions

TL;DR

This paper reports a lattice QCD calculation of B and Bs meson decay constants using maximally twisted Wilson fermions, interpolating between charm and bottom quark masses, and validating results with a novel ratio method.

Contribution

It introduces a calculation of heavy-light decay constants with maximally twisted Wilson fermions and employs a new ratio approach to interpolate to the physical b quark mass.

Findings

f_B=191(14) MeV

f_Bs=243(14) MeV

f_Bs/f_B=1.27(5)

Abstract

We present a lattice QCD calculation of the heavy-light decay constants f_B and f_Bs performed with Nf=2 maximally twisted Wilson fermions, at four values of the lattice spacing. The decay constants have been also computed in the static limit and the results are used to interpolate the observables between the charm and the infinite-mass sectors, thus obtaining the value of the decay constants at the physical b quark mass. Our preliminary results are f_B=191(14) MeV, f_Bs=243(14) MeV, f_Bs/f_B=1.27(5). They are in good agreement with those obtained with a novel approach, recently proposed by our Collaboration (ETMC), based on the use of suitable ratios having an exactly known static limit.