Nucleon form factors from quenched lattice QCD with domain wall fermions

Journal Article · Tue Jul 01 04:00:00 EDT 2008 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PHYSREVD.78.014510· OSTI ID:21250249

Sasaki, Shoichi ^[1]; Yamazaki, Takeshi ^[2]

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1. Department of Physics, University of Tokyo, Hongo 7-3-1, Tokyo 113-0033 (Japan)
2. Physics Department, University of Connecticut, Storrs, Connecticut 06269-3046 (United States)

We present a quenched lattice calculation of the weak nucleon form factors: vector [F{sub V}(q{sup 2})], induced tensor [F{sub T}(q{sup 2})], axial vector [F{sub A}(q{sup 2})] and induced pseudoscalar [F{sub P}(q{sup 2})] form factors. Our simulations are performed on three different lattice sizes L{sup 3}xT=24{sup 3}x32, 16{sup 3}x32, and 12{sup 3}x32 with a lattice cutoff of a{sup -1}{approx_equal}1.3 GeV and light quark masses down to about 1/4 the strange quark mass (m{sub {pi}}{approx_equal}390 MeV) using a combination of the DBW2 gauge action and domain wall fermions. The physical volume of our largest lattice is about (3.6 fm){sup 3}, where the finite volume effects on form factors become negligible and the lower momentum transfers (q{sup 2}{approx_equal}0.1 GeV{sup 2}) are accessible. The q{sup 2} dependences of form factors in the low q{sup 2} region are examined. It is found that the vector, induced tensor, and axial-vector form factors are well described by the dipole form, while the induced pseudoscalar form factor is consistent with pion-pole dominance. We obtain the ratio of axial to vector coupling g{sub A}/g{sub V}=F{sub A}(0)/F{sub V}(0)=1.219(38) and the pseudoscalar coupling g{sub P}=m{sub {mu}}F{sub P}(0.88m{sub {mu}}{sup 2})=8.15(54), where the errors are statistical errors only. These values agree with experimental values from neutron {beta} decay and muon capture on the proton. However, the root mean-squared radii of the vector, induced tensor, and axial vector underestimate the known experimental values by about 20%. We also calculate the pseudoscalar nucleon matrix element in order to verify the axial Ward-Takahashi identity in terms of the nucleon matrix elements, which may be called as the generalized Goldberger-Treiman relation.

• OSTI ID: 21250249
• Journal Information: Physical Review. D, Particles Fields, Journal Name: Physical Review. D, Particles Fields Journal Issue: 1 Vol. 78; ISSN PRVDAQ; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
BETA DECAY
CAPTURE
COUPLING
D QUARKS
DIPOLES
FORM FACTORS
GEV RANGE 01-10
GOLDBERGER-TREIMAN RELATION
LATTICE FIELD THEORY
MASS
MATRIX ELEMENTS
MEV RANGE 100-1000
MOMENTUM TRANSFER
MUONS
NEUTRONS
PIONS
PROTONS
QUANTUM CHROMODYNAMICS
S QUARKS
SIMULATION
U QUARKS