Long baseline neutrino experiments, mass hierarchy and delta(CP)

TL;DR

This paper evaluates the potential of long baseline neutrino experiments like T2K, NOvA, LBNE, and LAGUNA to determine neutrino mass hierarchy and CP violation, highlighting LAGUNA's superior sensitivity at specific energies.

Contribution

It provides a comparative analysis of multiple experiments' capabilities in identifying neutrino mass hierarchy and CP phase, including the potential for discovering nonstandard interactions.

Findings

LAGUNA offers the clearest distinction of mass hierarchy at 0.5 GeV.

LBNE can distinguish hierarchy at around 1 GeV, but less clearly.

NOvA's ability to determine hierarchy is less certain.

Abstract

We investigate the possibilities offered by the long baseline experiments T2K, No$\nu$a, LBNE and LAGUNA for the evaluation of the neutrino mass hierarchy and CP violating phase $\delta_{CP}$. We consider a neutrino and antineutrino energy in the interval [0.5,12] GeV. It is found that the clearest possible distinction between the two hierarchy signatures is provided by LAGUNA for an (anti)neutrino energy $E_{(\bar\nu)\nu}\simeq 0.5$ GeV in the $(\bar\nu_{\mu} \rightarrow \bar\nu_{\mu}) \nu_{\mu}\rightarrow \nu_{\mu}$ disappearance channel. For LBNE at $E_{\bar\nu}\simeq 1$ GeV the $\bar\nu_{\mu}\rightarrow \bar\nu_{\mu}$ channel may also provide a distinction, although not so clear, and for No$\nu$a this may be even less clear. These results are essentially the same for the $\theta_{23}$ first and second octant solutions. As for $\delta_{CP}$ determination, LAGUNA also offers the best chances at $E_{\bar\nu}\simeq 0.5$ GeV in the $\bar\nu_{\mu}\rightarrow \bar\nu_{e}$ channel with $\theta_{23}$ in either octant. Regarding nonstandard interactions, the best possibility for their investigation resides in No$\nu$a whose source-far detector distance can become a magic baseline if the hierarchy is normal for channels $\nu_{\mu}\rightarrow \nu_{\mu}$, $\bar\nu_{\mu}\rightarrow \bar\nu_{e}$, $\bar\nu_{\mu}\rightarrow \bar\nu_{\mu}$ with energy (8.9-9.1) GeV, (11.6-12) GeV, (8.8-12) GeV. If the hierarchy is inverse, magic baselines for No$\nu$a occur for $\nu_{\mu}\rightarrow \nu_{e}$, $\nu_{\mu}\rightarrow \nu_{\mu}$, and $\bar\nu_{\mu}\rightarrow \bar\nu_{\mu}$ with energy (11.8-12) GeV, (8.9-12.3) GeV, (8.8-8.9) GeV. For LAGUNA a magic baseline appears for the $\bar\nu_{\mu}\rightarrow \bar\nu_{\mu}$ channel only at (4.7-5.0) GeV in inverse hierarchy. We have also investigated a possible complementarity between T2K and No$\nu$a.