On detecting CP violation in a single neutrino oscillation channel at very long baselines

TL;DR

This paper proposes a method to detect CP violation in a single neutrino oscillation channel at very long baselines by observing shifts in the oscillation peak, with matter effects enhancing the signal.

Contribution

It introduces a novel approach to identify CP violation through peak shifts in neutrino oscillations at long baselines, considering both vacuum and matter effects.

Findings

CP violation causes a shift in the oscillation peak in the $ u_e$--$ u_$ appearance channel.

Matter effects amplify the peak shift, aiding detection.

Detection is feasible with accurate flux knowledge or known mixing angles.

Abstract

We propose a way of detecting CP violation in a single neutrino oscillation channel at very long baselines (on the order of several thousands of kilometers), given precise knowledge of the smallest mass-squared difference. It is shown that CP violation can be characterized by a shift in $L/E$ of the peak oscillation in the $\nu_e$--$\nu_\mu$ appearance channel, both in vacuum and in matter. In fact, matter effects enhance the shift at a fixed energy. We consider the case in which sub-GeV neutrinos are measured with varying baseline and also the case of a fixed baseline. For the varied baseline, accurate knowledge of the absolute neutrino flux would not be necessary; however, neutrinos must be distinguishable from antineutrinos. For the fixed baseline, it is shown that CP violation can be distinguished if the mixing angle $\theta_{13}$ were known.