Abstract

We carry out a feasibility study toward a lattice QCD calculation of the neutron electric dipole moment (NEDM) in the presence of the $\theta$ term using two different approaches. In the first method, we calculate the CP-odd electromagnetic form factor $F_3$, which becomes the NEDM in the zero momentum transfer limit. In the second method we directly extract the NEDM from the energy difference between spin-up and spin-down neutron states in the presence of a constant electric field, without expanding a small but non-zero $\theta$. In this talk we report the results with second approach numerically, employing the domain-wall quark action with the RG improved gauge action in quenched QCD at $a^{-1}\simeq 2$ GeV on a $16^3\times 32\times 16$ lattice, and further applying to the clover quark action at a similar lattice spacing and nucleon mass. We obtain good signals from both approaches. We also investigate size effects and boundary effects in this mehod.

ppt file