Behavior of Neutron Spin in Polarized Nuclear Target for the T-violation Search in Compound Nuclei

Small admixture of the weak interaction in the effective nucleon-nucleon interaction is extremely enhanced in the parity violating asymmetry in some of p-wave compound nuclear states induced by epithermal neutrons. Recent measurements of the spectroscopic factors in the entrance channel to the compound states support that the enhancement is caused as the result of the interference between the p-wave compound state and neighboring s-wave states. The fact suggests a new type of the extremely sensitive search for T-violation in the meson-nucleon coupling. The new search would be experimentally realized as the observation of neutron spin behavior on transmission through a polarized nuclear target. The behavior of neutron spin has been discussed at the lowest order approximation by employing the neutron forward scattering amplitude f defined as
f=A+Bσ·I+Cσ·k+Dσ·(k×I)
where σ, k, I are unit vectors parallel to the neutron spin, neutron momentum and nuclear spin, respectively, and the non-zero D signals the T-violation. In this formalism, I is assumed completely perpendicular to k.
In this paper, we discuss practical case involving misalignment and next leading terms for the experimental design under discussion for a possible installation at the J-PARC (program number KEK-2018S12).