Speaker
Description
Leptonic decay rates are used to extract the elements of the Cabibbo-Kobayashi-Maskawa matrix; reaching sub-per cent precision requires including isospin-breaking effects, i.e., electromagnetic effects and effects from the explicit difference between the up and down quark masses. One of the major sources of systematic error in computing leptonic decay rates in QCD+QED is electromagnetic power-law finite-volume effects, which are expected to be large for a wide class of finite-volume formulations of QED.
In this talk, we present a numerical study of finite-volume effects in the factorizable diagrams for the pion and kaon leptonic decay rates, using ensembles from the BMW Collaboration with N$_{f}=2+1+1$ staggered quarks and stout smearing at the physical pion mass. We focus our study on a single lattice spacing $a=0.1315$ fm and use four spatial extensions ranging from $3.2$ fm to $8.4$ fm.