We compute the axial, scalar, tensor and pseudoscalar isovector couplings of the nucleon as well as the induced tensor and pseudoscalar charges in lattice simulations with Nf=2 mass-degenerate non-perturbatively improved Wilson-Sheikholeslami-Wohlert fermions. The simulations are carried out down to a pion mass of 150 MeV and linear spatial lattice extents of up to 4.6 fm at three different lattice spacings ranging from approximately 0.08 fm to 0.06 fm. Possible excited state contamination is carefully investigated and finite volume effects are studied. The couplings, determined at these lattice spacings, are extrapolated to the physical pion mass. In this limit we find agreement with experimental results, where these exist, with the exception of the magnetic moment. A proper continuum limit could not be performed, due to our limited range of lattice constants, but no significant lattice spacing dependence is detected. Upper limits on discretization effects are estimated and these dominate the error budget.
@article{arxiv.1412.7336,
title = {Nucleon isovector couplings from $N_f=2$ lattice QCD},
author = {Gunnar S. Bali and Sara Collins and Benjamin Glässle and Meinulf Göckeler and Johannes Najjar and Rudolf H. Rödl and Andreas Schäfer and Rainer W. Schiel and Wolfgang Söldner and Andre Sternbeck},
journal= {arXiv preprint arXiv:1412.7336},
year = {2015}
}
Comments
22 pages, 31 Figures, v2: comparison with summation method added, minor typos corrected, legibility of figures improved, references added/updated