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Title: Axial-vector form factors of the nucleon from lattice QCD

Abstract

In this paper, we present results for the form factors of the isovector axial vector current in the nucleon state using large scale simulations of lattice QCD. The calculations were done using eight ensembles of gauge configurations generated by the MILC collaboration using the HISQ action with 2 + 1 + 1 dynamical flavors. These ensembles span three lattice spacings a ≈ 0.06 , 0.09, and 0.12 fm and light-quark masses corresponding to the pion masses M π ≈ 135, 225, and 310 MeV. High-statistics estimates allow us to quantify systematic uncertainties in the extraction of G A (Q 2) and the induced pseudoscalar form factor G P(Q 2) . We perform a simultaneous extrapolation in the lattice spacing, lattice volume and light-quark masses of the axial charge radius r A data to obtain physical estimates. Using the dipole ansatz to fit the Q 2 behavior we obtain r A | dipole = 0.49(3) fm , which corresponds to M A = 1.39(9) GeV , and is consistent with M A = 1.35(17) GeV obtained by the miniBooNE collaboration. The estimate obtained using the z -expansion is r A | z - expansion = 0.46(6) fm, and the combined resultmore » is r A | combined = 0.48(4) fm. Analysis of the induced pseudoscalar form factor G P (Q 2) yields low estimates for g* P and g πNN compared to their phenomenological values. To understand these, we analyze the partially conserved axial current (PCAC) relation by also calculating the pseudoscalar form factor. Lastly, we find that these low values are due to large deviations in the PCAC relation between the three form factors, and in the pion-pole dominance hypothesis.« less

Authors:
ORCiD logo [1];  [1];  [2]; ORCiD logo [1]; ORCiD logo [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Michigan State Univ., East Lansing, MI (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25); USDOE Laboratory Directed Research and Development (LDRD) Program
Contributing Org.:
Precision Neutron Decay Matrix Elements (PNDME) Collaboration
OSTI Identifier:
1415378
Alternate Identifier(s):
OSTI ID: 1411105
Report Number(s):
LA-UR-17-23678
Journal ID: ISSN 2470-0010; PRVDAQ; TRN: US1800780
Grant/Contract Number:  
AC52-06NA25396; AC02-05CH11231; KA-1401020
Resource Type:
Accepted Manuscript
Journal Name:
Physical Review D
Additional Journal Information:
Journal Volume: 96; Journal Issue: 11; Journal ID: ISSN 2470-0010
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Atomic and Nuclear Physics; Axial form factors, nucleons, lattice QCD

Citation Formats

Gupta, Rajan, Jang, Yong-Chull, Lin, Huey-Wen, Yoon, Boram, and Bhattacharya, Tanmoy. Axial-vector form factors of the nucleon from lattice QCD. United States: N. p., 2017. Web. doi:10.1103/PhysRevD.96.114503.
Gupta, Rajan, Jang, Yong-Chull, Lin, Huey-Wen, Yoon, Boram, & Bhattacharya, Tanmoy. Axial-vector form factors of the nucleon from lattice QCD. United States. doi:10.1103/PhysRevD.96.114503.
Gupta, Rajan, Jang, Yong-Chull, Lin, Huey-Wen, Yoon, Boram, and Bhattacharya, Tanmoy. Mon . "Axial-vector form factors of the nucleon from lattice QCD". United States. doi:10.1103/PhysRevD.96.114503. https://www.osti.gov/servlets/purl/1415378.
@article{osti_1415378,
title = {Axial-vector form factors of the nucleon from lattice QCD},
author = {Gupta, Rajan and Jang, Yong-Chull and Lin, Huey-Wen and Yoon, Boram and Bhattacharya, Tanmoy},
abstractNote = {In this paper, we present results for the form factors of the isovector axial vector current in the nucleon state using large scale simulations of lattice QCD. The calculations were done using eight ensembles of gauge configurations generated by the MILC collaboration using the HISQ action with 2 + 1 + 1 dynamical flavors. These ensembles span three lattice spacings a ≈ 0.06 , 0.09, and 0.12 fm and light-quark masses corresponding to the pion masses Mπ ≈ 135, 225, and 310 MeV. High-statistics estimates allow us to quantify systematic uncertainties in the extraction of GA (Q2) and the induced pseudoscalar form factor GP(Q2) . We perform a simultaneous extrapolation in the lattice spacing, lattice volume and light-quark masses of the axial charge radius rA data to obtain physical estimates. Using the dipole ansatz to fit the Q2 behavior we obtain rA |dipole = 0.49(3) fm , which corresponds to MA = 1.39(9) GeV , and is consistent with MA = 1.35(17) GeV obtained by the miniBooNE collaboration. The estimate obtained using the z -expansion is rA |z - expansion = 0.46(6) fm, and the combined result is rA | combined = 0.48(4) fm. Analysis of the induced pseudoscalar form factor GP (Q2) yields low estimates for g*P and gπNN compared to their phenomenological values. To understand these, we analyze the partially conserved axial current (PCAC) relation by also calculating the pseudoscalar form factor. Lastly, we find that these low values are due to large deviations in the PCAC relation between the three form factors, and in the pion-pole dominance hypothesis.},
doi = {10.1103/PhysRevD.96.114503},
journal = {Physical Review D},
number = 11,
volume = 96,
place = {United States},
year = {2017},
month = {12}
}

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