MeV Electrophilic Axion-like Particles from Sun

This work explores the production of an MeV-scale electrophilic axion-like particles (ALPs) by utilizing the monochromatic 5.5MeV photon resulting from the nuclear fusion processes in the Sun. These 5.5MeV photons can undergo the Compton-like scattering with the ambient electrons in the solar matter to produce a substantial flux of MeV ALPs. Upon reaching the Earth, such ALPs can be detected via the same electron coupling, offering a new opportunity for the dark matter (DM) direct detection experiments to probe the previously unexplored parameter regions. We show that the existing data of LZ, PandaX-4T, and Borexino can attain the sensitivities g ae 3.7 times 10-6, g ae 3.7 times 10-6 and g ae 1.7 times 10-6, respectively, for m a 1 MeV. An optimistic 200 tonne times year exposure by PandaX-xT can reach g ae 1.6 times 10-6 for most of the mass window m a < 1 MeV and even g ae 1.5 times 10-7 with m a approaching 1MeV. Despite the stringent constraints from different laboratory experiments and astrophysical observations, our obtained limits from LZ, PandaX-4T, and Borexino can probe new parameter regions, specifically in the mass window 0.4, MeV m a 1 MeV.