The ρ radiative decay width from lattice QCD

Abstract

Pion photoproduction constitutes a prototype process, which allows for the study of the electro-weak decay of a QCD-unstable state, the ρ resonance. It is also the most straightforward process to investigate such (resonant) transition matrix elements in lattice QCD. We performed a lattice calculation of the process ππ → ρ → πγ, at presently the lightest pion mass of 317 MeV and in a large box of size (3.6 fm)3. In addition to outlining the method for our calculation, we give account of our analysis of systematic uncertainties, with focus on parametrization dependence of the P−wave phase shift and the analytic continuation of our lattice data to the ρ resonance pole to extract the coupling |Gρπγ | = 0.0802 (38). © Copyright owned by the author(s) under the terms of the Creative Commons.