New Constraints on Axion-Like Particles with the NEON Detector at a Nuclear Reactor

TL;DR

This study uses the NEON detector near a nuclear reactor to set new experimental limits on axion-like particles, exploring previously untested parameter regions and demonstrating the potential for future reactor-based searches.

Contribution

It provides the first constraints on ALPs from the NEON experiment, improving existing bounds and exploring new mass and coupling parameter space.

Findings

No significant ALP signal was detected.

Limits on ALP-photon coupling reach 6.24×10⁻⁶ GeV⁻¹ at 3.0 MeV mass.

Limits on ALP-electron coupling reach 4.95×10⁻⁸ at 1.02 MeV mass.

Abstract

We report new constraints on axion-like particles (ALPs) using data from the NEON experiment, which features a 16.7 kg of NaI(Tl) target located 23.7 meters from a 2.8 GW thermal power nuclear reactor. Analyzing a total exposure of 3063 kg$\cdot$days, with 1596 kg$\cdot$days during reactor-on and 1467 kg$\cdot$days during reactor-off periods, we compared energy spectra to search for ALP-induced signals. No significant signal was observed, enabling us to set exclusion limits at the 95\% confidence level. These limits probe previously unexplored regions of the ALP parameter space, particularly for axion mass ($m_a$) near $1$ MeV/c$^2$. For ALP-photon coupling (${g_{a\gamma}}$), limits reach as low as 6.24$\times$ 10$^{-6}$ GeV$^{-1}$ at $m_a$ = 3.0 MeV/c$^2$, while for ALP-electron coupling (${g_{ae}}$), limits reach 4.95$\times$ 10$^{-8}$ at $m_a$ = 1.02 MeV/c$^2$. This work demonstrates the potential for future reactor experiments to probe unexplored ALP parameter space.