Dark Matter Capture by Atomic Nuclei

Abstract

We propose a new strategy to search for a particular type of dark matter via nuclear capture. If the dark matter particle carries baryon number, as motivated by a class of theoretical explanations of the matter-antimatter asymmetry of the universe, it can mix with the neutron and be captured by an atomic nucleus. The resulting state de-excites by emitting a single photon or a cascade of photons with a total energy of up to several MeV. The exact value of this energy depends on the dark matter mass. We investigate the prospects for detecting dark matter capture signals in current and future neutrino and dark matter direct detection experiments.

Coloured Scalar Mediated Nucleon Decays to Invisible Fermion

“…An interesting proposal to search for invisible fermions by their capture by atomic nuclei was done in Ref. [38] suggesting that the large volume neutrino experiments can be used for such searches. This opens up new possibility for searches at DUNE, and at various xenon experiment as explained by the authors [38].…”

“…In the case where the mass of invisible fermion is in the range (937.8 MeV, 938.8 MeV) proton decay is avoided, but neutron transition to χ is kinematically allowed. The lower bound on the mass of χ comes from the request that none of the stable nuclei can decay to dark matter, whereas the upper bound is necessary for the stability of χ [2,11,17]. In the case of experimental detection, the simplest way is to register photon of the energy 0.782 MeV < E γ < 1.664 MeV.…”

“…The main message of this study is that Borexino data restrict the branching ratio of the n → χγ to be smaller than 10 −4 . The existence of heavy neutron stars also gives the strong limits, since n → χγ would allow neutron stars to reach masses below the observed ones [17]. The colour scalar or vector mediation in the processes of interactions of the DM with the SM fermions were considered in varieties of the models (see eg.…”

Neutron's Dark Secret

“…Also in models with the neutron dark decay channel n → χ γ, a novel dark matter detection opportunity arises. Since the dark particle χ carries baryon number B χ = 1, it can be captured by atomic nuclei through its mixing with the neutron [61]. This is especially interesting when χ is the dark matter particle.…”

“…Thus, E c differs from the energy of the standard cascade triggered by neutron capture by (m n − m χ ). Prospects for detecting dark matter capture signals in large volume neutrino experiments like the Deep Underground Neutrino Experiment (DUNE) [62] and in dark matter direct detection experiments like PandaX [63] and XENON1T [64], were also investigated in [61], and the discovery reach is quite promising.…”