Neutrino lines from MeV dark matter annihilation and decay in JUNO

We discuss the discovery potential of JUNO experiment for neutrino lines from MeV dark matter (DM) annihilation and decay in a model-independent way. We find that JUNO will be able to give severe constraints on the cross section of DM annihilating into neutrinos and on the lifetime of DM decaying into neutrinos. More concretely, with 20 years of data-taking in the fiducial volume 17 kton, the cross section will be constrained smaller than 4 x 10-26 cm3 sec-1 for the mass of a DM particle 15 MeV <= mx <= 50 MeV at 90 % C.L., which might be strong enough to test thermal production mechanism of DM particles for such range of DM mass. The lifetime will be constrained as strong as 1 x 1024 sec for the mass of a DM particle mx ' 100 MeV at 90 % C.L..