Abstract
We present a high statistics study of the isovector nucleon charges and form factors using seven ensembles of 2+1-flavor Wilson-clover fermions. The axial vector and pseudoscalar form factors obtained on each of these ensembles satisfy the partially conserved axial current relation between them once the lowest energy Nπ excited state is included in the spectral decomposition of the correlation functions used for extracting the ground state matrix elements. Similarly, we find evidence that the Nππ excited state contributes to the correlation functions with the insertion of the vector current, consistent with the vector meson dominance model. The resulting form factors are consistent with the Kelly parametrization of the experimental electric and magnetic data. Our final estimates for the isovector charges are gAu-d=1.32(6)(5)sys, gSu-d=1.06(9)(6)sys, and gTu-d=0.97(3)(2)sys, where the first error is the overall analysis uncertainty and the second is an additional combined systematic uncertainty. The form factors yield: (i) the axial charge radius squared, «rA2»u-d=0.428(53)(30)sys fm2; (ii) the induced pseudoscalar charge, gP∗=7.9(7)(9)sys; (iii) the pion-nucleon coupling, gπNN=12.4(1.2); (iv) the electric charge radius squared, «rE2»u-d=0.85(12)(19)sys fm2; (v) the magnetic charge radius squared, «rM2»u-d=0.71(19)(23)sys fm2; and (vi) the magnetic moment, μu-d=4.15(22)(10)sys. All our results are consistent with phenomenological/experimental values but with larger errors. Last, we present a Padé parametrization of the axial, electric, and magnetic form factors over the range 0.04<Q2<1 GeV2 for phenomenological studies.
| Original language | English |
|---|---|
| Article number | 054505 |
| Journal | Physical Review D |
| Volume | 105 |
| Issue number | 5 |
| DOIs | |
| State | Published - Mar 1 2022 |
Funding
We thank V. Cirigliano and E. Mereghetti for many helpful discussions, and E. Ruiz Arriola for informing us of the current results for the pion-nucleon coupling. The calculations used the chroma software suite , the multigrid invertor for generating quark propagators , the QUDA library , and the multigrid with QUDA . This research used resources at (i) the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231; (ii) the Oak Ridge Leadership Computing Facility, which is a DOE Office of Science User Facility supported under Contract No. DE-AC05-00OR22725, and was awarded through the INCITE Program Projects No. PHY138 and No. HEP133, and ALCC Program Project No. LGT107; (iii) the USQCD Collaboration, which is funded by the Office of Science of the U.S. Department of Energy; and (iv) Institutional Computing at Los Alamos National Laboratory. T. B. and R. G. were partly supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Contract No. DE-AC52-06NA25396. B. J. is supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC05-06OR22725. F. W. is supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under Contract No. DE-AC05-06OR23177. We acknowledge support from the U.S. Department of Energy, Office of Science, Office of Advanced Scientific Computing Research and Office of Nuclear Physics, Scientific Discovery through Advanced Computing (SciDAC) program, and of the U.S. Department of Energy Exascale Computing Project. T. B., R. G., S. M., S. P., and B. Y. were partly supported by the LANL LDRD program, and S. P. by the Center for Nonlinear Studies.