複合核反応における111Cd 4.53 eV p波共鳴由来のγ線角度分布測定

In order to explain our universe, the existence of unknown CP violation is necessary. CP violation is equivalent to time reversal violation by assuming CPT invariance. We are planning to search for a new source of time reversal violation using compound nuclear reactions, in which a nucleus absorbs neutron and emits γ ray. It is experimentally observed that enhancement of parity violation by compound nuclear reactions is amplified by a factor of 10^6 compared to proton-proton scattering. This effect is considered due to s-p mixing, which is interference between tails of s-wave and p-wave. It is theoretically suggested that similarly enhancement mechanism can be applied to time reversal violation. In the theory, the magnitude of the enhancement for time reversal violation depends on a spin factor κ (J,ϕ) which has a different value for each nucleus, whose ϕ is a parameter of partial neutron width with j = 1/2, and j = 3/2. We performed a measurement to determine the κ(J,ϕ) of 111Cd in J-PARC MLF BL04. 111Cd is a strong candidate for a search for time reversal violation since it has a large enhancement factor for parity violation. We can determine κ(J,ϕ) using parameter ϕ, which is only determined by comparing calculation and experiment of shape change of p-wave resonance relying on the angle of emitted γ ray. We studied the shape change using γ ray energy measuring the angular distribution of γ rays emitted by compound nuclear reaction by using germanium detectors, and neutron energy acquired by using time of flight technique. We will present the result of the analysis for the determination of κ(J,ϕ) of 111Cd.