Multiparticle contribution to hadronic correlation functions using Chiral Perturbation Theory
Current and future lattice QCD simulations with physically light pion masses face new challenges. Multiparticle states with one or more pions are expected to cause sizable multiparticlestate contaminations in hadronic correlation functions, leading to possibly large systematic uncertainties in the observables computed by numerical simulations. Chiral perturbation theory, a lowenergy effective theory for QCD, can be used to compute analytically these multiparticlestate 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 multiparticlestate 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.
Principal Investigators
Bär, Oliver PD Dr. (Details) (Theoretical Physics / Phenomenology of Elementary Particles beyond the Standard Model) 

Financer
DFG: Eigene Stelle (Sachbeihilfe) 

Duration of Project
Start date: 02/2017
End date: 02/2020Research Areas
Particles, Nuclei and Fields Research Areas
Elementarteilchenphysik
Publications
Peerreviewed publications:
Nπstate contamination in lattice calculations of the nucleon pseudoscalar
form factors,
O. Bär, Phys. Rev. D 100, 054507 (2019).
Nπstate contamination in lattice calculations of the nucleon axial form factors,
O. Bär, Phys. Rev. D 99, 054506 (2019).
Threeparticle Nππstate contribution to the nucleon 2point function in lattice QCD,
O. Bär, Phys. Rev. D 97, 094507 (2018).
Chiral perturbation theory and nucleonpionstate contaminatons in lattice QCD,
O. Bär, International Journal of Modern Physics A, Vol. 32, 1730011 (2017).
Nucleonpionstate contribution in lattice calculations of moments of parton distribution functions,
O. Bär, Phys. Rev. D 95, no. 3, 034506 (2017).
Nucleonpionstate contribution in lattice calculations of the nucleon charges gA , gT and gS,
O. Bär, Phys. Rev. D 94, no. 5, 054505 (2016).
Conference proceedings:
Nucleonpionstate contamination in the lattice determination of the axial form factors of the nucleon,
O. Bär, PoS LAT2018 (2018) 061.
Multihadronstate contamination in nucleon observables from chiral perturbation theory,
O. Bär, EPJ Web Conf. 175 (2018) 01007.