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

Jeremy Green, Nesreen Hasan, Stefan Meinel, Michael Engelhardt, Stefan Krieg, Jesse Laeuchli, John Negele, Kostas Orginos, Andrew Pochinsky, and Sergey Syritsyn
Phys. Rev. D 95, 114502 – Published 14 June 2017

Abstract

We report a calculation of the nucleon axial form factors GAq(Q2) and GPq(Q2) for all three light quark flavors q{u,d,s} in the range 0Q21.2GeV2 using lattice QCD. This work was done using a single ensemble with pion mass 317 MeV and 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 GAq(Q2), we determine the quark contributions to the nucleon spin and axial radii. By extrapolating the isovector GPud(Q2), we obtain the induced pseudoscalar coupling relevant for ordinary muon capture and the pion-nucleon coupling constant. We find that the disconnected contributions to GP form factors are large, and give an interpretation based on the dominant influence of the pseudoscalar poles in these form factors.

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  • Received 28 March 2017

DOI:https://doi.org/10.1103/PhysRevD.95.114502

© 2017 American Physical Society

Physics Subject Headings (PhySH)

  1. Research Areas
Nuclear PhysicsParticles & Fields

Authors & Affiliations

Jeremy Green1,*, Nesreen Hasan2,3,†, Stefan Meinel4,5,‡, Michael Engelhardt6, Stefan Krieg2,3, Jesse Laeuchli7, John Negele8, Kostas Orginos9,10, Andrew Pochinsky8, and Sergey Syritsyn10

  • 1NIC, Deutsches Elektronen-Synchrotron, 15738 Zeuthen, Germany
  • 2Bergische Universität Wuppertal, 42119 Wuppertal, Germany
  • 3IAS, Jülich Supercomputing Centre, Forschungszentrum Jülich, 52425 Jülich, Germany
  • 4Department of Physics, University of Arizona, Tucson, Arizona 85721, USA
  • 5RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973, USA
  • 6Department of Physics, New Mexico State University, Las Cruces, New Mexico 88003-8001, USA
  • 7Department of Computer Science, College of William and Mary, Williamsburg, Virginia 23187, USA
  • 8Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
  • 9Physics Department, College of William and Mary, Williamsburg, Virginia 23187, USA
  • 10Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA

  • *jeremy.green@desy.de
  • n.hasan@fz-juelich.de
  • smeinel@email.arizona.edu

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Issue

Vol. 95, Iss. 11 — 1 June 2017

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