There and back again: Solar cycle effects in future measurements of low-energy atmospheric neutrinos

TL;DR

This study analyzes how solar cycle variations influence low-energy atmospheric neutrino measurements at DUNE and Hyper-Kamiokande, revealing significant time-dependent flux variations and their implications for neutrino oscillation studies.

Contribution

It provides the first detailed assessment of solar cycle effects on low-energy atmospheric neutrino fluxes at DUNE and HK, including oscillation impacts and statistical significance estimates.

Findings

Flux variation amplitude of about ±5% at DUNE and ±1% at HK.

Up/down event ratio varies from 0.45 to 0.85 at DUNE and 0.75 to 1.5 at HK.

Statistical significance of observing solar cycle modulation is 4.8σ at DUNE and 2.0σ at HK.

Abstract

We study the impact of time-dependent solar cycles in the atmospheric neutrino rate at DUNE and Hyper-Kamiokande (HK), focusing in particular on the flux below 1 GeV. Including the effect of neutrino oscillations for the upward-going component that travels through the Earth, we find that across the solar cycle the amplitude of time variation is about $\pm5\%$ at DUNE, and $\pm 1\%$ at HK. At DUNE, the ratio of up/down-going events ranges from 0.45 to 0.85, while at HK, it ranges from 0.75 to 1.5. Over the 11-year solar cycle, we find that the estimated statistical significance for observing time modulation of atmospheric neutrinos is $4.8\sigma$ for DUNE and $2.0\sigma$ for HK. Flux measurements at both DUNE and HK will be important for understanding systematics in the low-energy atmospheric flux as well as for understanding the effect of oscillations in low-energy atmospheric neutrinos.