T violation at a future neutrino factory

Wednesday 5 Nov 2025, 13:00 → 15:00 Asia/Tokyo

A228 (U. Toyama, Faculty of Science, Department of Physics)

We study the possibility of measuring T (time reversal) violation in a future long baseline neutrino oscillation experiment. By assuming a neutrino factory as a staging scenario of a muon collider at the J-PARC site, we find that the \nu_e \to \nu_\mu oscillation probabilities can be measured with a good accuracy at the Hyper-Kamiokande detector. By comparing with the probability of the time-reversal process, \nu_\mu \to \nu_e, measured at the T2K/T2HK experiments, one can determine the CP phase \delta in the neutrino mixing matrix if |\sin(\delta)| is large enough. The determination of \delta can be made with poor knowledge of the matter density of the earth as T violation is almost insensitive to the matter effects. The comparison of CP and T-violation measurements, {\it \`a la} the CPT theorem, provides us with a non-trivial check of the three neutrino paradigm based on the quantum field theory.