A high-statistics study of the nucleon EM form factors, axial charge and quark momentum fraction

B. Jäger*, T. D. Rae, S. Capitani, M. Della Morte, D. Djukanovic, G. von Hippel, B. Knippschild, H. B. Meyer, H. Wittig

*Corresponding author for this work

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Abstract

We present updated results for the nucleon axial charge and electromagnetic (EM) form factors, which include a significant increase in statistics for all ensembles (up to 4000 measurements), as well as the addition of ensembles with pion masses down to $m_\pi\sim195$ MeV. We also present results for the average quark momentum fraction. The new data allows us to perform a thorough study of the systematic effects encountered in the lattice extraction. We concentrate on systematic effects due to excited-state contaminations for each of the quantities, which we check using several different time separations between the operators at the source and sink through a comparison of plateau fits and the summed operator insertion method (which provides a mechanism to suppress the excited-state contamination). We confirm our earlier finding that a reliable extraction of the axial charge must be based on a method which eliminates excited-state contaminations. Similar conclusions apply to our EM form factor calculations . The measurements are calculated using the CLS ensembles with non-perturbatively O(a) improved Wilson fermions in $N_f=2$ QCD.
Original languageEnglish
JournalP o S - Proceedings of Science
Number of pages13
ISSN1824-8039
Publication statusPublished - 22. Nov 2013
Externally publishedYes
Event31st International Symposium on Lattice Field Theory LATTICE 2013: LATTICE 2013 - Mainz, Germany
Duration: 29. Jul 20133. Aug 2013

Conference

Conference31st International Symposium on Lattice Field Theory LATTICE 2013
CountryGermany
CityMainz
Period29/07/201303/08/2013

Bibliographical note

13 pages, 7 figures; talk presented at the 31st International Symposium on Lattice Field Theory (Lattice 2013), 29 July - 3 August 2013, Mainz, Germany; typos corrected, plots relabelled, conclusions unchanged

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