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 $4\times 10^{-26}\,{\rm cm^{3}\,sec^{-1}}$ for the mass of a DM particle $15\,{\rm MeV} \lesssim m_{\chi} \lesssim 50\,{\rm MeV}$ 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 $1\times 10^{24}\,{\rm sec}$ for the mass of a DM particle $m_{\chi} \simeq 100\,{\rm MeV}$ at $90\,\%$ C.L..