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

Here, we report a calculation of the nucleon axial form factors $$G_A^q(Q^2)$$ and $$G_P^q(Q^2)$$ for all three light quark flavors $$q\in\{u,d,s\}$$ in the range $$0\leq Q^2\lesssim 1.2\text{ GeV}^2$$ using lattice QCD. Our 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 $$G_A^q(Q^2)$$, 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 also found 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.
 [1] ;  [2] ;  [3] ;  [4] ;  [2] ;  [5] ;  [6] ;  [7] ;  [6] ;  [8]
  1. John von Neumann-Institute for Computing (NIC), Zeuthen (Germany)
  2. Bergische Univ., Wuppertal (Germany); Julich Research Centre (Germany). Inst. for Advanced Simulation (IAS)
  3. Univ. of Arizona, Tucson, AZ (United States). Dept. of Physics; Brookhaven National Lab. (BNL), Upton, NY (United States). RIKEN Research Center
  4. New Mexico State Univ., Las Cruces, NM (United States). Dept. of Physics
  5. College of William and Mary, Williamsburg, VA (United States). Dpet. of Computer Science
  6. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Center for Theoretical Physics
  7. College of William and Mary, Williamsburg, VA (United States). Physics Dept. ; Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
  8. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
Publication Date:
Report Number(s):
JLAB-THY-17-2498; DOE/OR/23177-4172; arXiv:1703.06703; RBRC 1232
Journal ID: ISSN 2470-0010; PRVDAQ
Grant/Contract Number:
FG02-94ER40818; SC-0011090; FG02-96ER40965; FC02-12ER41890; FG02-04ER41302; AC02-05HC11231; AC05-06OR23177; ACI-1053575; CCF-121834; PHY-1520996; SFB-TRR 55; FG02–94ER40818; SC–0011090; FG02–96ER40965; FC02–12ER41890; FG02–04ER41302; AC02–05HC11231; AC05–06OR23177
Accepted Manuscript
Journal Name:
Physical Review D
Additional Journal Information:
Journal Volume: 95; Journal Issue: 11; Journal ID: ISSN 2470-0010
American Physical Society (APS)
Research Org:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Country of Publication:
United States
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1363979