PoS - Proceedings of Science
Volume 396 - The 38th International Symposium on Lattice Field Theory (LATTICE2021) - Oral presentation
Nucleon-pion-state contamination in lattice computations of the nucleon electromagnetic form factors
O. Baer* and H. Colic
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Pre-published on: May 16, 2022
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The nucleon-pion-state contributions to QCD two-point and three-point functions relevant for lattice calculations of the nucleon electromagnetic form factors are studied in chiral perturbation theory.
To leading order the results depend on a few experimentally known low-energy constants only, and the nucleon-pion-state contribution to the form factors can be estimated. The nucleon-pion-state contribution to the electric form factor $G_{\rm E}(Q^2)$ is at the +5 percent level for a source-sink separation of 2 fm, and it increases with increasing momentum transfer $Q^2$. For the magnetic form factor the nucleon-pion-state contribution leads to an underestimation of $G_{\rm M}(Q^2)$ by about $-5$ percent that decreases with increasing $Q^2$.
For smaller source-sink separations that are accessible in present-day lattice simulations the impact is larger. Although the ChPT results may not be applicable for these time separations a comparison with recent lattice data works reasonably well.
DOI: https://doi.org/10.22323/1.396.0455
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