2026/07/23 by Shao-Feng Ge, Sk Jeesun, Tao Li
#hep-ph #astro-ph.HE #astro-ph.SR #hep-ex
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 gae \lesssim 3.7 × 10-6, gae \lesssim 3.7 × 10-6 and gae \lesssim 1.7 × 10-6, respectively, for ma \lesssim 1MeV. An optimistic 200 tonne×year exposure by PandaX-xT can reach gae\lesssim 1.6 × 10-6 for most of the mass window ma < 1MeV and even gae \lesssim 1.5 × 10-7 with ma 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 \rm MeV \lesssim ma \lesssim 1MeV.