skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Nucleon Charges from 2+1+1-flavor HISQ and 2+1-flavor clover lattices

Abstract

Precise estimates of the nucleon charges g A, g S and g T are needed in many phenomenological analyses of SM and BSM physics. In this talk, we present results from two sets of calculations using clover fermions on 9 ensembles of 2+1+1-flavor HISQ and 4 ensembles of 2+1-flavor clover lattices. In addition, we show that high statistics can be obtained cost-effectively using the truncated solver method with bias correction and the coherent source sequential propagator technique. By performing simulations at 4–5 values of the source-sink separation t sep, we demonstrate control over excited-state contamination using 2- and 3-state fits. Using the high-precision 2+1+1-flavor data, we perform a simultaneous fit in a, M π and M πL to obtain our final results for the charges.

Authors:
ORCiD logo [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Office of Science (SC); USDOE Laboratory Directed Research and Development (LDRD) Program
OSTI Identifier:
1356141
Report Number(s):
LA-UR-16-29008
Journal ID: ISSN 1824-8039
Grant/Contract Number:
AC52-06NA25396; AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
PoS Proceedings of Science
Additional Journal Information:
Journal Volume: 157; Conference: 34. Annual international symposium on lattice field theory (LATTICE2016), Southampton (United Kingdom), 24-30 Jul 2016; Journal ID: ISSN 1824-8039
Publisher:
SISSA
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Atomic and Nuclear Physics; Nucleon Charges

Citation Formats

Gupta, Rajan. Nucleon Charges from 2+1+1-flavor HISQ and 2+1-flavor clover lattices. United States: N. p., 2016. Web.
Gupta, Rajan. Nucleon Charges from 2+1+1-flavor HISQ and 2+1-flavor clover lattices. United States.
Gupta, Rajan. 2016. "Nucleon Charges from 2+1+1-flavor HISQ and 2+1-flavor clover lattices". United States. doi:. https://www.osti.gov/servlets/purl/1356141.
@article{osti_1356141,
title = {Nucleon Charges from 2+1+1-flavor HISQ and 2+1-flavor clover lattices},
author = {Gupta, Rajan},
abstractNote = {Precise estimates of the nucleon charges gA, gS and gT are needed in many phenomenological analyses of SM and BSM physics. In this talk, we present results from two sets of calculations using clover fermions on 9 ensembles of 2+1+1-flavor HISQ and 4 ensembles of 2+1-flavor clover lattices. In addition, we show that high statistics can be obtained cost-effectively using the truncated solver method with bias correction and the coherent source sequential propagator technique. By performing simulations at 4–5 values of the source-sink separation tsep, we demonstrate control over excited-state contamination using 2- and 3-state fits. Using the high-precision 2+1+1-flavor data, we perform a simultaneous fit in a, Mπ and MπL to obtain our final results for the charges.},
doi = {},
journal = {PoS Proceedings of Science},
number = ,
volume = 157,
place = {United States},
year = 2016,
month = 7
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
The DOI is not currently available

Save / Share:
  • We present high-statistics estimates of the isovector charges of the nucleon from four 2+1-flavor ensembles generated using Wilson-clover fermions with stout smearing and tree-level tadpole improved Symanzik gauge action at lattice spacingsmore » $a=0.114$ and $0.080$ fm and with $$M_\pi \approx 315$$ and 200 MeV. The truncated solver method with bias correction and the coherent source sequential propagator construction are used to cost-effectively achieve $O(10^5)$ measurements on each ensemble. Using these data, the analysis of two-point correlation functions is extended to include four states in the fits and of three-point functions to three states. Control over excited-state contamination in the calculation of the nucleon mass, the mass gaps between excited states, and in the matrix elements is demonstrated by the consistency of estimates using this multistate analysis of the spectral decomposition of the correlation functions and from simulations of the three-point functions at multiple values of the source-sink separation. Lastly, the results for all three charges, $$g_A$$, $$g_S$$ and $$g_T$$, are in good agreement with calculations done using the clover-on-HISQ lattice formulation with similar values of the lattice parameters.« less
    Cited by 1
  • Cited by 1
  • Cited by 1
  • Cited by 8
  • 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 weremore » 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 are 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