Testing MeV dark matter with neutrino detectors

Abstract

MeV particles have been advocated as Dark Matter (DM) candidates in different contexts. This hypothesis can be tested indirectly by searching for the Standard Model (SM) products of DM self-annihilations. As the signal from DM self-annihilations depends on the square of the DM density, we might expect a sizable flux of annihilation products from our galaxy. Neutrinos are the least detectable particles in the SM and a null signal in this channel would allow to set the most conservative bound on the total annihilation cross section. Here, we show that neutrino detectors with good energy resolution and low energy thresholds can not only set bounds on the annihilation cross section but actually test the hypothesis of the possible existence of MeV DM, i.e. test the values of the cross section required to explain the observed DM density. At present, the data in the (positron) energy interval MeV of the Super-Kamiokande experiment is already able to put a very stringent bound on the annihilation cross section for masses between ∼15-130 MeV. Future large experiments, like megaton water-Čerenkov or large scintillator detectors, will improve the present limits and, if MeV DM exists, would be able to detect it.PACS numbers: 14.60. St, 95.35.+d, 95.55.Vj

The next-generation liquid-scintillator neutrino observatory LENA

“…1 in [221]). Here we describe the analysis performed in [217] for the physics reach of the LENA detector. The excellent background rejection allows for a significant improvement on present bounds.…”

“…20 (taken from [217]), the expected signal and background spectra are shown for LENA in Pyhäsalmi after 10 years of data taking. Other locations return similar results.…”

“…The overall normalization of the flux is affected by the value of J avg,k , scaling as ρ k . For instance, for different profiles [218][219][220], astrophysical uncertainties can induce up to a factor of ∼100 (∼6) for annihilations [216,217] (decays [214]). For concreteness, in what follows we present results using the Navarro, Frenk and White (NFW) profile [219], with J avg,1 = 2 [214] and J avg,2 = 5 [216].…”

“…It has been shown [214,217], particularly for SuperKamiokande, that already present large neutrino detectors severely constrain the DM properties, namely annihilation cross section and lifetime and, depending on the DM profile assumed, exclude an important part of the parameter space (see Fig. 1 in [217], Fig.…”

“…In this section, and following and reviewing the approach of [214][215][216][217], we consider this case and evaluate the potential neutrino flux from DM annihilation (decay) in the whole Milky Way, which we compare with the relevant backgrounds for detection. In such a way, we obtain an estimate of the sensitivity on the DM annihilation cross section (lifetime) by LENA.…”