Partially connected contributions to baryon masses in QCD+QED

TL;DR

This paper investigates the impact of partially connected contributions in lattice QCD+QED simulations on baryon mass calculations, proposing a method to compute these effects using stochastic sources.

Contribution

It introduces a novel approach to evaluate partially connected contributions to baryon masses in lattice QCD+QED with C-periodic boundary conditions.

Findings

Partially connected contributions are significant in finite volume simulations.

A combined point and stochastic source method effectively computes these contributions.

Results help improve the accuracy of baryon mass calculations in lattice QCD+QED.

Abstract

Full QCD+QED simulations allow to evaluate isospin breaking corrections to hadron masses. With the openQxD code, we are able to perform these simulations employing C-periodic boundary conditions, implemented through a doubling of the physical lattice along one spatial direction. The use of these boundary conditions introduces non-zero Wick contractions between two quark or two antiquark fields, that, in the case of the computation of baryon masses, lead to partially connected additional contributions that we expect to vanish in the infinite volume limit. These contributions are challenging because they involve an all-to-all propagator connecting one point in the physical lattice and one in the mirror lattice. We present a way to compute these corrections to the $\Omega^-$ baryon mass using a combination of point and stochastic source inversions. This work is part of the program of the RC* collaboration.