cry-EDM測定:結晶内電場を利用したEDM測定
The permanent electric dipole moment(EDM) of fundamental particles such as neutrons signals the violation of time-reversal invariance. Time-reversal invariance is a good prove for CP violation search by CPT theorem(CPT=1).
Currently, the upper limit of neutron EDM is 3.0×10^(-26)[e・cm]. Then, some theories beyond the Standard Model(such like SUSY) predict that the magnitude of neutron EDM is 10^(-26)〜10^(-28). Because of that, we are challenging to measure it more precisely and to open the door for new physics.
The sensitivity of neutron EDM measurements depend on the magnitude of the applying electric field. Existence of EDM makes neutron spin precess around the electric field, so we measure it. There are two major methods of neutron EDM measurement, UCN storage method and crystal diffraction method. Now, we are working on the latter of these. In the UCN storage method, polarized UCN is confined in a vessel and strong voltage is applied there. On the other hand, we use the electric field in certain crystals which is extremely large compared with an artificial electric field in crystal diffraction method. As a first step, we are challenging to measure the internal electric field of crystals.
