Neutron electric dipole moment using $N_{f} =2+1+1$ twisted mass fermions

We evaluate the neutron electric dipole moment |d→N| using lattice QCD techniques. The gauge configurations analyzed are produced by the European Twisted Mass Collaboration using Nf=2+1+1 twisted mass fermions at one value of the lattice spacing of a≃0.082 fm and a light quark mass corresponding to mπ≃373 MeV. Our approach to extract the neutron electric dipole moment is based on the calculation of the CP-odd electromagnetic form factor F3(Q2) for small values of the vacuum angle θ in the limit of zero Euclidean momentum transfer Q2. The limit Q2→0 is realized either by adopting a parametrization of the momentum dependence of F3(Q2) and performing a fit or by employing new position space methods, which involve the elimination of the kinematical momentum factor in front of F3(Q2). The computation in the presence of a CP-violating term requires the evaluation of the topological charge Q. This is computed by applying the cooling technique and the gradient flow with three different actions, namely the Wilson, the Symanzik tree-level improved and the Iwasaki action. We demonstrate that cooling and gradient flow give equivalent results for the neutron electric dipole moment. Our analysis yields a value of |d→N|=0.045(6)(1)θ¯e·fm for the ensemble with mπ=373 MeV considered.

Note:

Version accepted for publication in Phys. Rev. D.: 33 pages, 13 Figures

n: electric moment
quark: mass: twist
quark: mass dependence
form factor: electromagnetic
charge: topological
flow: Yang-Mills
lattice field theory
quantum chromodynamics
momentum dependence
tree approximation

References(67)

Figures(17)

[1]

The Neutron EDM in the SM: A Review

Shahida Dar
(
- ICTP, Trieste
)

e-Print:
- hep-ph/0008248

[2]

Electric dipole moments as probes of new physics

Maxim Pospelov
(
- Guelph U. and
- Perimeter Inst. Theor. Phys. and
- IPP, Canada
)
,
Adam Ritz
(
- CERN
)

- Annals Phys. 318 (2005) 119-169
•
e-Print:
- hep-ph/0504231
•
DOI:
- 10.1016/j.aop.2005.04.002

[3]

The neutron Electric Dipole Moment experiment at the Paul Scherrer Institute

nEDM

Collaboration

•

V. Helaine
(
- Caen U. and
- PSI, Villigen
)

for the collaboration.

- EPJ Web Conf. 73 (2014) 07003
•
DOI:
- 10.1051/epjconf/20147307003

[4]

An Improved experimental limit on the electric dipole moment of the neutron

C.A. Baker
(
- Rutherford and
- Sussex U. and
- Laue-Langevin Inst.
)
,
D.D. Doyle
(
- Rutherford and
- Sussex U. and
- Laue-Langevin Inst.
)
,
P. Geltenbort
(
- Rutherford and
- Sussex U. and
- Laue-Langevin Inst.
)
,
K. Green
(
- Rutherford and
- Sussex U. and
- Laue-Langevin Inst.
)
,
M.G.D. van der Grinten
(
- Rutherford and
- Sussex U. and
- Laue-Langevin Inst.
)

et al.

- Phys.Rev.Lett. 97 (2006) 131801
•
e-Print:
- hep-ex/0602020
•
DOI:
- 10.1103/PhysRevLett.97.131801

[5]

Reply to comment on `An Improved experimental limit on the electric dipole moment of the neutron'

C.A. Baker
(
- Rutherford and
- Sussex U. and
- Laue-Langevin Inst.
)
,
D.D. Doyle
(
- Rutherford and
- Sussex U. and
- Laue-Langevin Inst.
)
,
P. Geltenbort
(
- Rutherford and
- Sussex U. and
- Laue-Langevin Inst.
)
,
K. Green
(
- Rutherford and
- Sussex U. and
- Laue-Langevin Inst.
)
,
M.G.D. van der Grinten
(
- Rutherford and
- Sussex U. and
- Laue-Langevin Inst.
)

et al.

- Phys.Rev.Lett. 98 (2007) 149102
•
e-Print:
- 0704.1354
•
DOI:
- 10.1103/PhysRevLett.98.149102

[6]

CP Violating Effects in QCD

Varouzhan Baluni
(
- MIT, LNS
)

- Phys.Rev.D 19 (1979) 2227-2230
•
DOI:
- 10.1103/PhysRevD.19.2227

[7]

Chiral Estimate of the Electric Dipole Moment of the Neutron in Quantum Chromodynamics

- Phys.Lett.B 88 (1979) 123,
- Phys.Lett.B 91 (1980) 487 (erratum)
•
DOI:
- 10.1016/0370-2693(79)90128-X

[8]

Can Confinement Ensure Natural CP Invariance of Strong Interactions?

- Nucl.Phys.B 166 (1980) 493-506
•
DOI:
- 10.1016/0550-3213(80)90209-6

[9]

The Soft Pion Skyrmion Lagrangian and Strong {CP} Violation

Howard J. Schnitzer
(
- Harvard U. and
- Brandeis U.
)

- Phys.Lett.B 139 (1984) 217-222
•
DOI:
- 10.1016/0370-2693(84)91248-6

[10]

THE ELECTRIC DIPOLE MOMENT OF THE NEUTRON IN A GAUGE THEORY

E.P. Shabalin
(
- Moscow, ITEP
)

- Sov.Phys.Usp. 26 (1983) 297,
- Usp.Fiz.Nauk 139 (1983) 561-585,
- Moscow Inst. Theor. Exp. Phys. Gkae - ITPF-82-065 (82,REC. JUL. ) 60 P. (208317
•
DOI:
- 10.1070/PU1983v026n04ABEH004331