Learning about the CP phase in the next 10 years

TL;DR

This paper evaluates the future sensitivity of accelerator and reactor experiments to the lepton CP phase, using a global measure to quantify the fraction of the phase space that can be excluded.

Contribution

It introduces the CP exclusion fraction measure to assess how well upcoming experiments can constrain the CP phase in neutrino oscillations.

Findings

T2K and NOvA can exclude 30-40% of the CP phase space at 3σ after 5 years.

Mass hierarchy determination is feasible for a limited parameter space at 3σ.

The combined experiments improve sensitivity to the CP phase and mass hierarchy.

Abstract

We assess the sensitivity to the lepton CP phase by accelerator and reactor experiments in the near future, characterizing it globally by means of the CP exclusion fraction measure. Such measure quantifies what fraction of the $\delta_{\rm CP}$ space can be excluded at given input values of $\theta_{23}$ and $\delta_{\rm CP}$. For some region of the parameter space, we find that T2K and NO$\nu$A combined can exclude about $30\%-40\%$ of the $\delta_{\rm CP}$ space at $3\sigma$ with a 5 years running in each neutrino and antineutrino modes. A determination of the mass hierarchy would be possible for a modest portion of the parameter space at $3\sigma$.