Search for Solar Flare Neutrinos with the KamLAND detector

TL;DR

This study searched for neutrinos associated with solar flares using KamLAND data from 2002 to 2019, setting new upper limits on neutrino fluence but detecting no significant signals.

Contribution

It provides the first constraints on solar flare neutrino fluence over a large dataset, exploring previously unconstrained parameter space.

Findings

No statistically significant neutrino excess detected.

Established upper limits on electron anti-neutrino and neutrino fluence.

Expanded the parameter space for solar flare neutrino searches.

Abstract

We report the result of a search for neutrinos in coincidence with solar flares from the GOES flare database. The search was performed on a 10.8 kton-year exposure of KamLAND collected from 2002 to 2019. This large exposure allows us to explore previously unconstrained parameter space for solar flare neutrinos. We found no statistical excess of neutrinos and established 90% confidence level upper limits of $8.4 \times 10^7$ cm$^{-2}$ ($3.0 \times 10^{9}$ cm$^{-2}$) on electron anti-neutrino (electron neutrino) fluence at 20 MeV normalized to the X12 flare, assuming that the neutrino fluence is proportional to the X-ray intensity.