Effect of Leptonic CP Phase in nu_mu --> nu_mu Oscillations

TL;DR

This paper explores how to measure the leptonic CP phase using muon neutrino oscillations alone, identifying optimal conditions and experimental setups that can detect CP violation effects independently of electron neutrino data.

Contribution

It demonstrates the feasibility of measuring the leptonic CP phase through muon neutrino oscillations alone, identifying optimal energies, baselines, and experimental configurations.

Findings

CP phase measurable around 0.43 GeV and 5000 km baseline

CP sensitivity persists even after energy averaging

Potential to determine CP phase with combined measurements in T2KK setup

Abstract

In the case of large 1-3 mixing angle as sin^2(2theta13 > 0.03, we investigate the possibility for measuring the leptonic CP phase by using only nu_mu --> nu_mu oscillations independently of nu_mu --> nu_e oscillations. As the result, we find that the CP phase can be measured best around the energy E=0.43 GeV and the baseline length L=5000km without strongly depending on the uncertainties of other parameters. In this region, the CP phase effect remains even after averaging over neutrino energy. We also find that there is the CP sensitivity even in the short baseline length L < 1000 km if Delta m_{31}^2 is determined with the uncertainty of about 0.1 . In the T2KK experiment, we explore the possibility for determining Delta m_{31}^2 by using one baseline from Tokai to Korea and then measuring the CP phase by using the baseline to Kamioka. As the result, we find that some information of the CP phase can be obtained from both measurements.