Hidden MeV-Scale Dark Matter in Neutrino Detectors

Abstract

The possibility of direct detection of light fermionic dark matter in neutrino detectors is explored from a model-independent standpoint. We consider all operators of dimension six or lower which can contribute to the interaction $\bar{f}p\to e^{+}n$, where $f$ is a dark Majorana or Dirac fermion. Constraints on these operators are then obtained from the $f$ lifetime and its decays which produce visible $\gamma$ rays or electrons. We find one operator which would allow $\bar{f}p\to e^{+}n$ at interesting rates in neutrino detectors, as long as $m_f\lesssim m_{\pi }$. The existing constraints on light dark matter from relic density arguments, supernova cooling rates, and big-bang nucleosynthesis are then reviewed. We calculate the cross-section for $\bar{f}p\to e^{+}n$ in neutrino detectors implied by this operator, and find that Super-K can probe the new physics scale $\Lambda$ for this interaction up to $\mathcal{O}(100TeV)$

Comments: 17 pages, 2 figures; v2: added reference, fixed typos, small changes in wording