Lattice QCD calculation of form factors describing the rare decays $B \to K^* \ell^+ \ell^-$ and $B_s \to ϕ\ell^+ \ell^-$

Abstract

The rare decays $B^0 \to K^{*0} μ^+ μ^-$ and $B_s \to ϕμ^+ μ^-$ are now being observed with enough precision to test Standard Model predictions. A full understanding of these decays requires accurate determinations of the corresponding hadronic form factors. Here we present results of lattice QCD calculations of the $B \to K^*$ and $B_s \to ϕ$ form factors; we also determine the form factors relevant for the tree-level decays $B_s \to K^* \ell ν$. We use full-QCD configurations including 2+1 flavors of sea quarks using an improved staggered action, and we employ lattice non-relativistic QCD to describe the bottom quark.

23 pages. Version 3 (accepted to Phys. Rev. D) includes interpolations to the physical strange quark mass. Central values shift by less than 1 sigma. Tables and figures updated accordingly