A Lattice Study of Spin and Flavour Symmetry in Heavy Quark Physics

TL;DR

This paper tests heavy quark spin-flavour symmetries in semi-leptonic B decays using lattice QCD, finding small corrections near charm mass for some form factors but significant deviations for others.

Contribution

First lattice QCD analysis of heavy quark symmetry effects in semi-leptonic B decays, quantifying 1/m_Q corrections at charm mass.

Findings

Small 1/m_Q corrections for protected form factors near charm

30-40% corrections for h_V and h_V/h_{A_{1}}

Supports validity of heavy quark symmetry at charm scale

Abstract

We present a first test of heavy quark spin-flavour symmetries in matrix elements for semi-leptonic decays \bar B to D l\bar\nu and \bar B to D^* l\bar\nu. We show that O(1/m_Q) corrections are small at masses around the charm for form factors protected by Luke's Theorem, but are of order 30-40 \% for h_V and h_V/h_{A_{1}}.