On Possibility of Determining Neutrino Mass Hierarchy by the Charged-Current and Neutral-Current Events of Supernova Neutrinos in Scintillation Detectors

TL;DR

This paper proposes a new method to determine the neutrino mass hierarchy by comparing inverse beta decay and neutral current event ratios of supernova neutrinos in scintillation detectors, analyzing phase-dependent flavor conversions.

Contribution

It introduces a novel approach using event ratio changes between accretion and cooling phases to identify the neutrino mass hierarchy based on flavor conversion effects.

Findings

The event ratio differs significantly between hierarchies during supernova phases.

The method can distinguish hierarchies by analyzing phase-dependent event ratio changes.

Flavor conversion effects are key to determining the hierarchy in scintillation detectors.

Abstract

One of the unresolved mysteries in neutrino physics is the neutrino mass hierarchy. We present a new method to determine neutrino mass hierarchy by comparing the events of inverse beta decays (IBD), $\bar{\nu}_e + p\rightarrow n + e^+$, and neutral current (NC) interactions, $\nu(\overline{\nu}) + p\rightarrow\nu(\overline{\nu}) + p$, of supernova neutrinos from accretion and cooling phases in scintillation detectors. Supernova neutrino flavor conversions depend on the neutrino mass hierarchy. On account of Mikheyev-Smirnov-Wolfenstein effects, the full swap of $\bar{\nu}_e$ flux with the $\bar{\nu}_x$ ($x=\mu,~\tau$) one occurs in the inverted hierarchy, while such a swap does not occur in the normal hierarchy. In consequence, the ratio of high energy IBD events to NC events for the inverted hierarchy is higher than in the normal hierarchy. Since the luminosity of $\bar{\nu}_e$ is larger than that of $\nu_x$ in accretion phase while the luminosity of $\bar{\nu}_e$ becomes smaller than that of $\nu_x$ in cooling phase, we calculate this ratio for both accretion and cooling phases. By analyzing the change of this event ratio from accretion phase to cooling phase, one can determine the neutrino mass hierarchy.