Abstract: Light sub-GeV dark matter (DM) constitutes an underexplored target, beyond the optimized sensitivity of typical direct DM detection experiments. We comprehensively investigate hadrophilic light DM produced from cosmic-ray collisions with the atmosphere. The resulting relativistic DM, originating from meson decays, can be efficiently observed in variety of experiments, such as XENON1T. We include for the first time decays of eta, eta' and K+ mesons, leading to improved limits for DM masses above few hundred MeV. We incorporate an exact treatment of the DM attenuation in Earth and demonstrate that nuclear form factor effects can significantly impact the resulting testable DM parameter space. Further, we establish projections for upcoming experiments, such as DARWIN, over a wide range of DM masses below the GeV scale.

Abstract: As dark matter (DM) direct detection experiments continue to improve their sensitivity they will inevitably encounter an irreducible background arising from coherent neutrino scattering. This so-called “neutrino floor” may significantly reduce the sensitivity of an experiment to DM-nuclei interactions, particularly if the recoil spectrum of the neutrino background is approximately degenerate with the DM signal. This occurs for the conventionally considered spin-independent (SI) or spin-dependent (SD) interactions. In such case, an increase in the experiment's exposure by multiple orders of magnitude may not yield any significant increase in sensitivity. The typically considered SI and SD interactions, however, do not adequately reflect the whole landscape of the well-motivated DM models, which includes other interactions. Since particle DM has not been detected yet in laboratories, it is essential to understand and maximize the detection capabilities for a broad variety of possible models and signatures. In this work we explore the impact of the background arising from various neutrino sources on the discovery potential of a DM signal for a large class of viable DM-nucleus interactions and several potential futuristic experimental settings, with different target elements. For some momentum suppressed cross sections, large DM particle masses and heavier targets, we find that there is no suppression of the discovery limits due to neutrino backgrounds. Further, we explicitly demonstrate that inelastic scattering, which could appear in models with multicomponent dark sectors, would help to lift the signal degeneracy associated with the neutrino floor. This study could assist with mapping out the optimal DM detection strategy for the next generation of experiments.

Abstract: The next Galactic core-collapse supernova (SN) is a highly anticipated observational target for neutrino telescopes. However, even prior to collapse, massive dying stars shine copiously in “pre-supernova” (pre-SN) neutrinos, which can potentially act as efficient SN warning alarms and provide novel information about the very last stages of stellar evolution. We explore the sensitivity to pre-SN neutrinos of large-scale direct dark matter detection experiments, which, unlike dedicated neutrino telescopes, take full advantage of coherent neutrino-nucleus scattering. We find that argon-based detectors with target masses of O(100)tons (i.e., comparable in size to the proposed ARGO experiment) operating at sub-keV thresholds can detect O(10-100) pre-SN neutrinos coming from a source at a characteristic distance of similar to 200 pc, such as Betelgeuse (alpha Orionis). Large-scale xenon-based experiments with similarly low thresholds could also be sensitive to pre-SN neutrinos. For a Betelgeuse-type source, large-scale dark matter experiments could provide a SN warning siren similar to 10 hours prior to the explosion. We also comment on the complementarity of large-scale direct dark matter detection experiments and neutrino telescopes in the understanding of core-collapse SN.