Multi-particle contribution to hadronic correlation functions using Chiral Perturbation Theory

Current and future lattice QCD simulations with physically light pion masses face new challenges. Multi-particle states with one or more pions are expected to cause sizable multi-particle-state contaminations in hadronic correlation functions, leading to possibly large systematic uncertainties in the observables computed by numerical simulations. Chiral perturbation theory, a low-energy effective theory for QCD, can be used to compute analytically these multi-particle-state contaminations. In this project we perform these perturbative calculations at leading order for various hadronic structure observables (e.g. the axial and the tensor charge of the nucleon, the quark momentum fraction in the nucleon and the axial and electromagnetic form factors). Our final results can be used to analytically remove the multi-particle-state contaminations for these observables in the analysis of numerical lattice data, thus removing an uncertainty that otherwise would result in a systematic error that is hard to quantify.