Form factors for Lambda_b to Lambda transitions from lattice QCD

Abstract

The rare baryonic decays Lb !Lm+m? and Lb !Lg can complement rare B meson decays in constraining models of new physics. In this work, we calculate the relevant Lb ! L transition form factors at leading order in heavy-quark effective theory using lattice QCD. Our analysis is based on RBC/UKQCD gauge field ensembles with 2+1 flavors of domain-wall fermions, and with lattice spacings of a?0:11 fm and a?0:08 fm. We compute appropriate ratios of three-point and two-point correlation functions for a wide range of source-sink separations, and extrapolate to infinite separation in order to eliminate excited-state contamination. We then extrapolate the form factors to the continuum limit and to the physical values of the light-quark masses.