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.

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.

Duration of project

Start date: 02/2017

End date: 02/2020

Research Areas

Research Areas

Publications

Peer-reviewed publications:

Nπ-state contamination in lattice calculations of the nucleon pseudoscalar form factors,

O. Bär, Phys. Rev. D 100, 054507 (2019).

Nπ-state contamination in lattice calculations of the nucleon axial form factors,

O. Bär, Phys. Rev. D 99, 054506 (2019).

Three-particle Nππ-state contribution to the nucleon 2-point function in lattice QCD,

O. Bär, Phys. Rev. D 97, 094507 (2018).

Chiral perturbation theory and nucleon-pion-state contaminatons in lattice QCD,

O. Bär, International Journal of Modern Physics A, Vol. 32, 1730011 (2017).

Nucleon-pion-state contribution in lattice calculations of moments of parton distribution functions,

O. Bär, Phys. Rev. D 95, no. 3, 034506 (2017).

Nucleon-pion-state contribution in lattice calculations of the nucleon charges gA , gT and gS,

O. Bär, Phys. Rev. D 94, no. 5, 054505 (2016).

Conference proceedings:

Nucleon-pion-state contamination in the lattice determination of the axial form factors of the nucleon,

O. Bär, PoS LAT2018 (2018) 061.

Multi-hadron-state contamination in nucleon observables from chiral perturbation theory,

O. Bär, EPJ Web Conf. 175 (2018) 01007.