Chiral corrections and lattice QCD results for fBs/fBd and ΔmBs/ΔmBd

It has been argued recently that the inclusion of the chiral logarithms in extrapolation of the lattice data can shift the value of the hadronic parameter xi = f(Bs) rootB(Bs) / f(Bd) rootB(Bd), from 1.16(6) to 1.32(10) and even higher. If true, that would considerably change the theoretical estimate for the ratio of oscillation frequencies in the B-s(0)- and B-d(0)-systems, and would affect the standard CKM unitarity triangle analysis. In this Letter we show that f(Bs)/f(Bd) approximate to f(K) / f(pi) and thus the uncertainty due to the missing chiral logs is smaller than previously thought. By combining the NLO chiral expansion with the static heavy quark limit we obtain xi = 1.22(9). (C) 2003 Elsevier Science B.V. All rights reserved.