Neutron electric dipole moment from lattice QCD

Journal Article · Fri Jul 01 00:00:00 EDT 2005 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PhysRevD.72.014504· OSTI ID:20711064

Shintani, E; Kanaya, K ^[1]; Aoki, S ^[1]; Ishizuka, N; Kuramashi, Y; Taniguchi, Y; Ukawa, A; Yoshie, T ^[1]; Kikukawa, Y ^[2]; Okawa, M ^[3]

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1. Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571 (Japan)
2. Department of Physics, Nagoya University, Nagoya 464-8602 (Japan)
3. Department of Physics, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan)

We carry out a feasibility study for the lattice QCD calculation of the neutron electric dipole moment (NEDM) in the presence of the {theta} term. We develop the strategy to obtain the nucleon EDM from the CP-odd electromagnetic form factor F{sub 3} at small {theta}, in which NEDM is given by lim{sub q{sup 2}}{sub {yields}}{sub 0}{theta}F{sub 3}(q{sup 2})/(2m{sub N}), where q is the momentum transfer and m{sub N} is the nucleon mass. We first derive a formula which relates F{sub 3}, a matrix element of the electromagnetic current between nucleon states, with vacuum expectation values of nucleons and/or the current. In the expansion of {theta}, the parity-odd part of the nucleon-current-nucleon three-point function contains contributions not only from the parity-odd form factors but also from the parity-even form factors multiplied by the parity-odd part of the nucleon two-point function, and, therefore, the latter contribution must be subtracted to extract F{sub 3}. We then perform an explicit lattice calculation employing the domain-wall quark action with the renormalization group improved gauge action in quenched QCD at a{sup -1}{approx_equal}2 GeV on a 16{sup 3}x32x16 lattice. At the quark mass m{sub f}a=0.03, corresponding to m{sub {pi}}/m{sub {rho}}{approx_equal}0.63, we accumulate 730 configurations, which allow us to extract the parity-odd part in both two- and three-point functions. Employing two different Dirac {gamma} matrix projections, we show that a consistent value for F{sub 3} cannot be obtained without the subtraction described above. We obtain F{sub 3}(q{sup 2}{approx_equal}0.58 GeV{sup 2})/(2m{sub N})=-0.024(5)e{center_dot}fm for the neutron and F{sub 3}(q{sup 2}{approx_equal}0.58 GeV{sup 2})/(2m{sub N})=0.021(6)e{center_dot}fm for the proton.

• OSTI ID: 20711064
• Journal Information: Physical Review. D, Particles Fields, Vol. 72, Issue 1; Other Information: DOI: 10.1103/PhysRevD.72.014504; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA). CP-PACS Collaboration; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ALGEBRAIC CURRENTS
CP INVARIANCE
CURRENT ALGEBRA
ELECTRIC DIPOLE MOMENTS
ELECTROMAGNETIC FORM FACTORS
FEASIBILITY STUDIES
GEV RANGE
LATTICE FIELD THEORY
MATRIX ELEMENTS
MOMENTUM TRANSFER
NEUTRONS
P INVARIANCE
PARITY
PROTONS
QUANTUM CHROMODYNAMICS
QUARKS
RENORMALIZATION
REST MASS