Computing the nucleon charge and axial radii directly at ${Q}^{2}=0$ in lattice QCD
We describe a procedure for extracting momentum derivatives of nucleon matrix elements on the lattice directly at Q ^{2} = 0 . This is based on the Rome method for computing momentum derivatives of quark propagators. We apply this procedure to extract the nucleon isovector magnetic moment and charge radius as well as the isovector induced pseudoscalar form factor at Q ^{2} = 0 and the axial radius. For comparison, we also determine these quantities with the traditional approach of computing the corresponding form factors, i.e. G$$v\atop{E}$$ (Q ^{2}) and G$$v\atop{M}$$ (Q ^{2}) for the case of the vector current and G$$v\atop{P}$$ (Q ^{2}) and G$$v\atop{A}$$ (Q ^{2}) for the axial current, at multiple Q ^{2} values followed by zexpansion fits. We perform our calculations at the physical pion mass using a 2HEXsmeared Wilsonclover action. To control the effects of excitedstate contamination, the calculations were done at three sourcesink separations and the summation method was used. The derivative method produces results consistent with those from the traditional approach but with larger statistical uncertainties especially for the isovector charge and axial radii.
 Authors:

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 Bergische Univ. Wuppertal (Germany); Forschungszentrum Julich (Germany)
 Deutsches ElektronenSynchrotron (DESY), Zeuthen (Germany)
 Univ. of Arizona, Tucson, AZ (United States); Brookhaven National Lab. (BNL), Upton, NY (United States)
 New Mexico State Univ., Las Cruces, NM (United States)
 Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
 Brookhaven National Lab. (BNL), Upton, NY (United States); Stony Brook Univ., NY (United States)
 Publication Date:
 Grant/Contract Number:
 FC0206ER41444; FG0296ER40965; SC0011090
 Type:
 Published Article
 Journal Name:
 Physical Review D
 Additional Journal Information:
 Journal Volume: 97; Journal Issue: 3; Journal ID: ISSN 24700010
 Publisher:
 American Physical Society (APS)
 Research Org:
 Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); New Mexico State Univ., Las Cruces, NM (United States)
 Sponsoring Org:
 USDOE Office of Science (SC)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Particles & Fields; Nuclear Physics
 OSTI Identifier:
 1420034
 Alternate Identifier(s):
 OSTI ID: 1501522
Hasan, Nesreen, Green, Jeremy, Meinel, Stefan, Engelhardt, Michael, Krieg, Stefan, Negele, John, Pochinsky, Andrew, and Syritsyn, Sergey. Computing the nucleon charge and axial radii directly at Q2=0 in lattice QCD. United States: N. p.,
Web. doi:10.1103/physrevd.97.034504.
Hasan, Nesreen, Green, Jeremy, Meinel, Stefan, Engelhardt, Michael, Krieg, Stefan, Negele, John, Pochinsky, Andrew, & Syritsyn, Sergey. Computing the nucleon charge and axial radii directly at Q2=0 in lattice QCD. United States. doi:10.1103/physrevd.97.034504.
Hasan, Nesreen, Green, Jeremy, Meinel, Stefan, Engelhardt, Michael, Krieg, Stefan, Negele, John, Pochinsky, Andrew, and Syritsyn, Sergey. 2018.
"Computing the nucleon charge and axial radii directly at Q2=0 in lattice QCD". United States.
doi:10.1103/physrevd.97.034504.
@article{osti_1420034,
title = {Computing the nucleon charge and axial radii directly at Q2=0 in lattice QCD},
author = {Hasan, Nesreen and Green, Jeremy and Meinel, Stefan and Engelhardt, Michael and Krieg, Stefan and Negele, John and Pochinsky, Andrew and Syritsyn, Sergey},
abstractNote = {We describe a procedure for extracting momentum derivatives of nucleon matrix elements on the lattice directly at Q2 = 0 . This is based on the Rome method for computing momentum derivatives of quark propagators. We apply this procedure to extract the nucleon isovector magnetic moment and charge radius as well as the isovector induced pseudoscalar form factor at Q2 = 0 and the axial radius. For comparison, we also determine these quantities with the traditional approach of computing the corresponding form factors, i.e. G$v\atop{E}$ (Q2) and G$v\atop{M}$ (Q2) for the case of the vector current and G$v\atop{P}$ (Q2) and G$v\atop{A}$ (Q2) for the axial current, at multiple Q2 values followed by zexpansion fits. We perform our calculations at the physical pion mass using a 2HEXsmeared Wilsonclover action. To control the effects of excitedstate contamination, the calculations were done at three sourcesink separations and the summation method was used. The derivative method produces results consistent with those from the traditional approach but with larger statistical uncertainties especially for the isovector charge and axial radii.},
doi = {10.1103/physrevd.97.034504},
journal = {Physical Review D},
number = 3,
volume = 97,
place = {United States},
year = {2018},
month = {2}
}