Transverse Polarization of Muons in K⁺ --> π⁰ μ⁺ ν Decay as a test of Time Reversal Invariance

Time Reversal Invariance (T) , with its origins in microscopic reversibility, has received renewed interest in modern physics as a constituent of CPT symmetry. CP symmetry and T symmetry also play a role in the models of primordial synthesis. So far, CP and T violations are found only in neutral meson sectors (K0 and B0 decays) and the amount of CP violation, while accounted for by the Standard Model (SM), is not enough to describe baryogenesis. This situation, along with other unsatisfactory features of the SM, makes it necessary that we find additional sources of CP (T) violation.  
   Following the suggestion by Sakurai, transverse polarization measurements in K-decays were carried out over several years as a test of the T-invariance. The latest measurement was the E-246 experiment at the 12 GeV proton synchrotron of the National High Energy Accelerator Research Organization (KEK), Tsukuba, Japan. I will present the measurement details and the final results of this experiment.
   The construction of a high intensity 50 GeV proton accelerator (J-PARC), a joint project of Japan Atomic Energy Research Institute and KEK, gives us an opportunity to do an experiment with at least about 20-fold increase in sensitivity. A proposal to perform such an experiment with an upgraded E246 detector is being prepared. I will present these details and anticipated physics outcomes.