Proton and neutron electromagnetic form factors using $N_f$=2+1+1 twisted-mass fermions with physical values of the quark masses

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Auteurs principaux: Alexandrou, Constantia, Bacchio, Simone, Koutsou, Giannis, Prasad, Bhavna, Spanoudes, Gregoris
Format: Preprint
Publié: 2025
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author Alexandrou, Constantia
Bacchio, Simone
Koutsou, Giannis
Prasad, Bhavna
Spanoudes, Gregoris
author_facet Alexandrou, Constantia
Bacchio, Simone
Koutsou, Giannis
Prasad, Bhavna
Spanoudes, Gregoris
contents We compute the electromagnetic form factors of the proton and neutron using lattice QCD with $N_f = 2 + 1 + 1$ twisted mass clover-improved fermions and quark masses tuned to their physical values. Three ensembles with lattice spacings of $a$=0.080 fm, 0.068 fm, and 0.057 fm, and approximately the same physical volume allow us to obtain the continuum limit directly at the physical pion mass. Several values of the source-sink time separation ranging from 0.5 fm to 1.5 fm are used, enabling a thorough analysis of excited state effects via multi-state fits. The disconnected contributions are analyzed using high statistics for the two-point functions combined with low-mode deflation and hierarchical probing for the fermion loop estimation. We study the momentum dependence of the form factors using the z-expansion and dipole Ansaetze, thereby enabling the extraction of the electric and magnetic radii, as well as the magnetic moments in the continuum limit, for which we provide preliminary results.
format Preprint
id arxiv_https___arxiv_org_abs_2502_11301
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Proton and neutron electromagnetic form factors using $N_f$=2+1+1 twisted-mass fermions with physical values of the quark masses
Alexandrou, Constantia
Bacchio, Simone
Koutsou, Giannis
Prasad, Bhavna
Spanoudes, Gregoris
High Energy Physics - Lattice
We compute the electromagnetic form factors of the proton and neutron using lattice QCD with $N_f = 2 + 1 + 1$ twisted mass clover-improved fermions and quark masses tuned to their physical values. Three ensembles with lattice spacings of $a$=0.080 fm, 0.068 fm, and 0.057 fm, and approximately the same physical volume allow us to obtain the continuum limit directly at the physical pion mass. Several values of the source-sink time separation ranging from 0.5 fm to 1.5 fm are used, enabling a thorough analysis of excited state effects via multi-state fits. The disconnected contributions are analyzed using high statistics for the two-point functions combined with low-mode deflation and hierarchical probing for the fermion loop estimation. We study the momentum dependence of the form factors using the z-expansion and dipole Ansaetze, thereby enabling the extraction of the electric and magnetic radii, as well as the magnetic moments in the continuum limit, for which we provide preliminary results.
title Proton and neutron electromagnetic form factors using $N_f$=2+1+1 twisted-mass fermions with physical values of the quark masses
topic High Energy Physics - Lattice
url https://arxiv.org/abs/2502.11301