Up, down, and strange nucleon axial form factors from lattice QCD

We report a calculation of the nucleon axial form factors G(A)(q)(Q(2)) and G(A)(q)(Q(2)) for all three light quark flavors q is an element of{u, d, s} in the range 0 <= Q(2) less than or similar to 1.2 GeV2 using lattice QCD. This work was done using a single ensemble with pion mass 317 MeVand made use of the hierarchical probing technique to efficiently evaluate the required disconnected loops. We perform nonperturbative renormalization of the axial current, including a nonperturbative treatment of the mixing between light and strange currents due to the singlet-nonsinglet difference caused by the axial anomaly. The form factor shapes are fit using the model-independent z expansion. From G(A)(q)(Q(2)), we determine the quark contributions to the nucleon spin and axial radii. By extrapolating the isovector G(P)(u-d)(Q(2)), we obtain the induced pseudoscalar coupling relevant for ordinary muon capture and the pion-nucleon coupling constant. We find that the disconnected contributions to G(P) form factors are large, and give an interpretation based on the dominant influence of the pseudoscalar poles in these form factors.Office of Science of the U.S. Department of Energy; National Science Foundation [ACI-1053575, CCF-121834, PHY-1520996]; Forschungszentrum Julich; U.S. Department of Energy Office of Nuclear Physics [DE-FG02-94ER40818, DE-SC-0011090, DE-FG02-96ER40965, DE-FC02-12ER41890, DE-FG02-04ER41302, DE-AC02-05HC11231, DE-AC05-06OR23177]; RIKEN Foreign Postdoctoral Researcher program; RIKENBNL Research Center; Deutsche Forschungsgemeinschaft [SFB-TRR 55]; PRISMA Cluster of Excellence at the University of MainzThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu