Search for CP Violation at a Neutrino Factory in a Four-Neutrino Model

TL;DR

This paper investigates CP violation in long baseline neutrino oscillations within a four-neutrino framework, highlighting the small matter effects compared to genuine CP violation, and providing analytic expressions for probability differences.

Contribution

It introduces an analytic approach to study CP violation effects in a four-neutrino model, including matter effects, which differ from the three-neutrino case.

Findings

Matter effects are small compared to genuine CP violation.

Analytic expressions for probability differences are derived.

CP violation effects are studied in a four-neutrino scenario.

Abstract

The CP violation effects in long baseline neutrino oscillations are studied in the framework of a four-neutrino model (three active neutrinos and one sterile neutrino). It is assumed that neutrino masses are devided into two nearly degenerate pairs, as indicated by the oscillation data. Approximative analytic expressions are derived for the probability differences $\Delta P_{\a\b} \equiv P(\nu_\alpha \to \nu_\beta)- P(\bar\nu_\alpha \to \bar\nu_\beta)$ taking into account the CP violation effect of the Earth's crust. The matter effect is found to be small compared with the genuine CP violation term, in contrast with the three-neutrino model.