Lattice HQET with exponentially improved statistical precision

TL;DR

This paper presents a new lattice discretization for static quarks that significantly improves statistical precision, enabling accurate B-meson property calculations at large Euclidean times.

Contribution

It introduces an alternative static quark discretization with exponential error reduction, allowing precise B-meson correlation functions and decay constants computation.

Findings

Statistical fluctuations are reduced exponentially with Euclidean time.

B-meson decay constants are determined with good precision at multiple lattice spacings.

Finite b-quark mass effects are estimated by combining static results with D_s meson data.

Abstract

We introduce an alternative discretization for static quarks on the lattice retaining the O(a) improvement properties of the Eichten-Hill action. In this formulation, statistical fluctuations are reduced by a factor which grows exponentially with Euclidean time, x_0. For the first time, B-meson correlation functions are computed with good statistical precision in the static approximation for x_0>1 fm. At lattice spacings a \approx 0.1 fm, a \approx 0.08 fm and a \approx 0.07 fm the B_s-meson decay constant is determined in static and quenched approximations. A correction due to the finite mass of the b-quark is estimated by combining these static results with a recent determination of F_Ds.