LAUSR

We report new constraints on axionlike particles (ALPs) using data from the NEON experiment, which features 16.7 kg of NaI(Tl) target located 23.7 m from a 2.8 GW thermal power nuclear reactor. Analyzing a total exposure of 3063  kg·day, with 1596  kg·day during reactor-on and 1467  kg·day 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 masses (m_{a}) near 1  MeV/c^{2}. For ALP-photon coupling (g_{aγ}), limits reach as low as 6.24×10^{-6}  GeV^{-1} at m_{a}=3.0  MeV/c^{2}, while for ALP-electron coupling (g_{ae}), limits reach 4.95×10^{-8} at m_{a}=1.02  MeV/c^{2}. This Letter demonstrates the potential for future reactor experiments to probe unexplored ALP parameter space.