T violation at a future neutrino factory

Abstract

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, $\grave{a}la$ the CPT theorem, provides us with a non-trivial check of the three neutrino paradigm based on the quantum field theory.

Comments: 25 pages, 10 figures, version accepted in JHEP