Probing high-energy solar axion flux with a large scintillation neutrino detector

TL;DR

This paper explores the potential of the JUNO neutrino detector to detect high-energy solar axions produced in nuclear reactions, forecasting improved sensitivity over current bounds through detailed numerical analysis.

Contribution

It provides the first detailed sensitivity forecast for solar axion detection at JUNO, considering multiple detection channels and axion couplings in a model-independent framework.

Findings

JUNO could improve current axion bounds by about an order of magnitude.

Multiple detection channels enhance the sensitivity to axion couplings.

JUNO has the best sensitivity among neutrino experiments for solar axion detection.

Abstract

We investigate the 5.49 MeV solar axions flux produced in the $p(d,\, ^{3}{\rm He})a$ reaction and analyze the potential to detect it with the forthcoming large underground neutrino oscillation experiment Jiangmen Underground Neutrino Observatory (JUNO). The JUNO detector could reveal axions through various processes such as Compton and inverse Primakoff conversion, as well as through their decay into two photons or electron-positron pairs inside the detector. We perform a detailed numerical analysis in order to forecast the sensitivity on different combinations of the axion-electron ($ g_{ae} $), axion-photon ($g_{a\gamma}$), and isovector axion-nucleon ($ g_{3aN} $) couplings, using the expected JUNO data for different benchmark values of axion mass in a model-independent way. We find that JUNO would improve by approximately one order of magnitude current bounds by Borexino and it has the best sensitivity among neutrino experiments.