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Title: Axial, scalar, and tensor charges of the nucleon from 2 + 1 + 1 -flavor lattice QCD

Here, we present results for the isovector axial, scalar, and tensor charges g u–d A, g u–d S, and g u–d T of the nucleon needed to probe the Standard Model and novel physics. The axial charge is a fundamental parameter describing the weak interactions of nucleons. The scalar and tensor charges probe novel interactions at the TeV scale in neutron and nuclear β-decays, and the flavor-diagonal tensor charges g u T, g d T, and g s T are needed to quantify the contribution of the quark electric dipole moment (EDM) to the neutron EDM. The lattice-QCD calculations were done using nine ensembles of gauge configurations generated by the MILC Collaboration using the highly improved staggered quarks 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 315 MeV. High-statistics estimates on five ensembles using the all-mode-averaging method allow us to quantify all systematic uncertainties and perform a simultaneous extrapolation in the lattice spacing, lattice volume, and light-quark masses for the connected contributions. Our final estimates, in the ¯MS scheme at 2 GeV, of the isovector charges aremore » g u–d A = 1.195(33)(20), g u–d S = 0.97(12)(6), and g u–d T = 0.987(51)(20). The first error includes statistical and all systematic uncertainties except that due to the extrapolation Ansatz, which is given by the second error estimate. Combining our estimate for gu–dS with the difference of light quarks masses (m d–m u) QCD = 2.67(35) MeV given by the Flavor Lattice Average Group, we obtain (M N – M P) QCD = 2.59(49) MeV. Estimates of the connected part of the flavor-diagonal tensor charges of the proton are g u T = 0.792(42) and g d T = –0.194(14). Combining our new estimates with precision low-energy experiments, we present updated constraints on novel scalar and tensor interactions, ε S,T, at the TeV scale.« less
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  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Univ. of Washington, Seattle, WA (United States)
  3. Univ. of California, Berkeley, CA (United States)
Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 2470-0010; PRVDAQ; TRN: US1701629
Grant/Contract Number:
AC52-06NA25396; KA-1401020; AC02-05CH11231; FG02-97ER4014
Accepted Manuscript
Journal Name:
Physical Review D
Additional Journal Information:
Journal Volume: 94; Journal Issue: 5; Journal ID: ISSN 2470-0010
American Physical Society (APS)
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
Contributing Orgs:
Precision Neutron Decay Matrix Elements (PNDME) Collaboration
Country of Publication:
United States