Correlated, Precision Measurements of \theta_{23} and $\delta$ using only the Electron Neutrino Appearance Experiments

TL;DR

This paper proposes a new method to simultaneously measure the leptonic CP phase δ and the mixing angle θ_{23} using only electron neutrino appearance data, significantly improving the precision of θ_{23} determination.

Contribution

The paper introduces a novel approach that uses spectral information to resolve a new degeneracy, enabling more accurate simultaneous measurement of θ_{23} and δ.

Findings

θ_{23} can be determined with six times higher accuracy than δ.

Spectral information around oscillation maxima effectively resolves the degeneracy.

The method achieves high-precision measurements using only electron neutrino appearance channels.

Abstract

Precision measurement of the leptonic CP violating phase $\delta$ will suffer from the, then surviving, large uncertainty of sin^2 \theta_{23} of 10-20% in the experimentally interesting region near maximal mixing of \theta_{23}. We advocate a new method for determination of both \theta_{23} and $\delta$ at the same time using only the \nu_e and \bar{\nu}_e appearance channels, and show that sin^2 \theta_{23} can be determined automatically with much higher accuracy, approximately a factor of six, than \sin \delta. In this method, we identify a new degeneracy for the simultaneous determination of \theta_{23} and \delta, the \theta_{23} intrinsic degeneracy, which must be resolved in order to achieve precision measurement of these two parameters. Spectral information around the vacuum oscillation maxima is shown to be the best way to resolve this degeneracy.