Lattice HQET with exponentially improved statistical precision

AbstractWe 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, x0. For the first time, B-meson correlation functions are computed with good statistical precision in the static approximation for x0>1 fm. At lattice spacings a≈0.1, 0.08, 0.07 fm, the Bs-meson decay constant is determined in the combined static and quenched approximation. A correction due to the finite mass of the b-quark is estimated by interpolating between the static result and a recent determination of FDs