The neutrino signal at HALO: learning about the primary supernova neutrino fluxes and neutrino properties

TL;DR

This paper analyzes supernova neutrino fluxes and their detection at HALO, showing how event ratios can reveal properties of neutrino fluxes and supernova core processes, despite uncertainties in neutrino physics.

Contribution

It provides analytical predictions of supernova neutrino signals at HALO, highlighting the sensitivity of event ratios to flux parameters and supernova neutrino transport.

Findings

Event ratios are sensitive to neutrino flux pinching parameters.

HALO can constrain supernova neutrino flux characteristics.

Event ratios provide insights into neutrino transport in supernovae.

Abstract

Core-collapse supernova neutrinos undergo a variety of phenomena when they travel from the high neutrino density region and large matter densities to the Earth. We perform analytical calculations of the supernova neutrino fluxes including collective effects due to the neutrino-neutrino interactions, the Mikheev-Smirnov-Wolfenstein (MSW) effect due to the neutrino interactions with the background matter and decoherence of the wave packets as they propagate in space. We predict the numbers of one- and two-neutron charged and neutral-current electron-neutrino scattering on lead events. We show that, due to the energy thresholds, the ratios of one- to two-neutron events are sensitive to the pinching parameters of neutrino fluxes at the neutrinosphere, almost independently of the presently unknown neutrino properties. Besides, such events have an interesting sensitivity to the spectral split features that depend upon the presence/absence of energy equipartition among neutrino flavors. Our calculations show that a lead-based observatory like the Helium And Lead Observatory (HALO) has the potential to pin down important characteristics of the neutrino fluxes at the neutrinosphere, and provide us with information on the neutrino transport in the supernova core.