# 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

Research output: Contribution to journalConference articleResearchpeer-review

## 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 language English P o S - Proceedings of Science 13 1824-8039 Published - 22. Nov 2013 Yes 31st International Symposium on Lattice Field Theory LATTICE 2013: LATTICE 2013 - Mainz, GermanyDuration: 29. Jul 2013 → 3. Aug 2013

### Conference

Conference 31st International Symposium on Lattice Field Theory LATTICE 2013 Germany Mainz 29/07/2013 → 03/08/2013

### 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