出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：We report on a direct lattice calculation of the neutron EDM(NEDM) using the external electric
field method in both quenched and full QCD. In quenched QCD, we use a 243
32 lattice at
b
2
6 with the Iwasaki gauge action and the clover fermion action to examine the viability of
this method. In particular we investigate possible effects of violation of the periodic boundary
condition of the external electric field on the NEDM signal. We also study the quark mass dependence
of NEDM in quenched QCD, and observe that NEDM seems to remain non-zero toward
the chiral limit because of the quenched artifact. In 2-flavor full QCD we employ configurations
generated by the CP-PACS collaboration on a 243
48 lattice at b
2
1 with the same gluon
and quark actions as in the quenched case. Since the number of configurations is limited, we
employ 8 different source points per one configuration and take an average over them. Our preliminary
result at three quark masses (mPS mV
0
81
0
76
0
69) indicates that non-zero value
for NEDM can be obtained in full QCD. Statistical errors, however, are still too large to show the
theoretically expected behaviour for NEDM in full QCD that it vanishes in the chiral limit.
