Laboratory for Particle Properties (Phi-lab)
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Experiment of CP violation in compound nucleus

In the initial universe, matters and anti-matters are generated, but now there are matters. It is thought that it is due to the difference between matters and anti-matters. This difference arise from "CP violation" and is confirmed by experiments. However, the amplitude of CP violation in the experiments is greatly different from estimation in standerd model. This is one of unresolved issues in moderm physics.

We appriach CP violation by searching Tviolation in compound nucleus resonance absorption reaction. Time reversal symmetry means "Physical law is not changed by time reversal." This symmetry is same as CP symmetry in CPT theorem. So we can know about CP violation in detail by measuring T violation precisely.

When nucleus absorb neutron, become intermediate state called "compound nucleus" and move to final state. Cross section of this reaction become large at specific energy and it called"compound nucleus resonance." In compound nucleus resonance absorption reaction, P violation is known to be amplified (compound nucleus model.) Now, it is theoretically suggested that T violation is amplified by same mechanism in P violation.

We plan mesurment of T violation by this theory. T violation can be measured by observing the change of the cross section due to the polarization direction in the compound nucleus resonance absorption reaction between polarized nuclei and polarized neutrons.

Now, we varidate the compound neucleus model and evaluate mesurment sensitivity for T violation by mesuring γ ray emitted when neucleus catch neutron.
Neutron spin polarization filter at BL04 in J-PARC.

Also, for high precision and efficiency of experiment, we deverop some technique as shown below,