High-Precision f_{Bs} and HQET from Relativistic Lattice QCD

by Nilmani Mathur

Friday 28 Oct 2011, 11:30 → 12:30 Asia/Kolkata

A-304 (Colaba Campus)

C. McNeile, C. T. H. Davies, E. Follana, K. Hornbostel, G. P. Lepage We present a new determination of the $B_s$ leptonic decay constant from lattice QCD simulations that use gluon configurations from MILC and a highly improved discretization of the relativistic quark action for both valence quarks. Our result, $f_{B_s} = 0.225(4)$\,GeV, is almost three times more accurate than previous determinations. We analyze the dependence of the decay constant on the heavy quark's mass and obtain the first empirical evidence for the leading $1/\sqrt{m_h}$ dependence predicted by Heavy Quark Effective Theory (HQET). As a check, we use our analysis technique to calculate the $m_{B_s}-m_{\eta_b}/2$ mass difference. Our result agrees with experiment to within errors of $11\,\mathrm{MeV}$ (better than 2%). We discuss how to extend our analysis to other quantities in $B_s$ and $B$ physics, making 2%-precision possible for the first time.

Paper http://arxiv.org/abs/arXiv:1110.4510