Isospin Violating Hadronic Mass Splittings using Lattice QCD+QED

Abstract

The composition and structure of matter has excited scientific thought for millennia. One of the highlights of the previous century was the development of the theories of quantum chromodynamics (QCD) and quantum electrodynamics (QED), which reveal an even deeper layer of structure than the atom and the nucleon. We use the non-perturbative method of lattice QCD+QED to make precision estimates of the masses and mass splittings of the light ground state hadron spectrum, including pseudoscalar mesons, octet baryons and decuplet baryons. We replicate this same analysis for ground state charmed hadrons. In these studies the QED component is necessary for two reasons. Firstly, it is necessary when attempting to obtain mass results with sub-percent precision. While secondly, it is essential in determining mass splittings between hadrons, QED is a substantial component of the mass splittings within an isospin multiplet, such as the baryons. Our ndings provide new insight into these splittings by separating the contributions arising from strong and electromagnetic e ects. We use lattice QCD+QED to determine the avour-neutral pseudoscalar meson masses, which incorporate disconnected quark line diagrams. We provide estimates of the absolute mass and mass splitting of the lowest two states, near a point of quark mass degeneracy. We show that QED plays an important role in the avour composition of states around points of approximate quark mass degeneracy, which is important at the physical quark mass and charge.