Probing mass orderings in presence of a very light sterile neutrino in a liquid argon detector

TL;DR

This paper investigates how the presence of a light sterile neutrino affects the determination of neutrino mass orderings using a liquid argon detector with beam and atmospheric neutrinos, considering different sterile mass ranges.

Contribution

It provides a detailed analysis of mass ordering sensitivity in the presence of a sterile neutrino across a broad mass squared difference range, including combined source studies for enhanced sensitivity.

Findings

Sterile neutrinos can obscure active neutrino mass ordering determination.

Resonant matter effects enhance sensitivity to sterile neutrino parameters.

Combined beam and atmospheric data improve mass ordering resolution.

Abstract

Results from experiments like LSND and MiniBooNE hint towards the possible presence of an extra eV scale sterile neutrino. The addition of such a neutrino will significantly impact the standard three flavour neutrino oscillations. In particular, it can give rise to additional degeneracies due to additional sterile parameters. For an eV scale sterile neutrino, the cosmological constraints dictate that the sterile state is heavier than the three active states. However, for lower masses of sterile neutrinos, it can be lighter than one and/or more of the three states. In such cases, the mass ordering of the sterile neutrinos also becomes unknown along with the mass ordering of the active states. In this paper, we explore the mass ordering sensitivity in the presence of a sterile neutrino assuming the mass squared difference $|\Delta_{41}|$ to be in the range $10^{-4} - 1$ eV$^2$. We study (i) how the ordering of the active states, i.e. the determination of the sign of $\Delta_{31}$ gets affected by the presence of a sterile neutrino in the above mass range, (ii) the possible determination of the sign of $\Delta_{41}$ for $\Delta_{41}$ in the range $10^{-4} - 0.1$ eV$^2$. This analysis is done in the context of a liquid argon detector using both beam neutrinos traveling a distance of 1300 km and atmospheric neutrinos which propagates through a distance ranging from 10 - 10000 km allowing resonant matter effects. Apart from presenting separate results from these sources, we also do a combined study and probe the synergy between these two in giving an enhanced sensitivity.