Abstract. We present a comprehensive review of keV-scale sterile neutrino Dark Matter, collecting views and insights from all disciplines involved -cosmology, astrophysics, nuclear, and particle physics -in each case viewed from both theoretical and experimental/observational perspectives. After reviewing the role of active neutrinos in particle physics, astrophysics, and cosmology, we focus on sterile neutrinos in the context of the Dark Matter puzzle. Here, we first review the physics motivation for sterile neutrino Dark Matter, based on challenges and tensions in purely cold Dark Matter scenarios. We then round out the discussion by critically summarizing all known constraints on sterile neutrino Dark Matter arising from astrophysical observations, laboratory experiments, and theoretical considerations. In this context, we provide a balanced discourse on the possibly positive signal from X-ray observations. Another focus of the paper concerns the construction of particle physics models, aiming to explain how sterile neutrinos of keV-scale masses could arise in concrete settings beyond the Standard Model of elementary particle physics. The paper ends with an extensive review of current and future astrophysical and laboratory searches, highlighting new ideas and their experimental challenges, as well as future perspectives for the discovery of sterile neutrinos.

A: Nuclear recoil events produced by neutron scatters form one of the most important classes of background in WIMP direct detection experiments, as they may produce nuclear recoils that look exactly like WIMP interactions. In DarkSide-50, we both actively suppress and measure the rate of neutron-induced background events using our neutron veto, composed of a boron-loaded liquid scintillator detector within a water Cherenkov detector. This paper is devoted to the description of the neutron veto system of DarkSide-50, including the detector structure, the fundamentals of event reconstruction and data analysis, and basic performance parameters.

A: A Geant4-based Monte Carlo package named G4DS has been developed to simulate the response of DarkSide-50, an experiment operating since 2013 at LNGS, designed to detect WIMP interactions in liquid argon. In the process of WIMP searches, DarkSide-50 has achieved two fundamental milestones: the rejection of electron recoil background with a power of ∼10 7 , using the pulse shape discrimination technique, and the measurement of the residual 39 Ar contamination in underground argon, ∼3 orders of magnitude lower with respect to atmospheric argon. These results rely on the accurate simulation of the detector response to the liquid argon scintillation, its ionization, and electron-ion recombination processes. This work provides a complete overview of the DarkSide Monte Carlo and of its performance, with a particular focus on PARIS, the custommade liquid argon response model.

Patient participation in treatment decisions can have positive effects on patient satisfaction, compliance and health outcomes. The objectives of this study were to examine attitudes of psoriasis patients regarding participation in treatment decisions and to evaluate the effect of a decision-aid for discussing treatment options. A "quasi experiment" was conducted in a large dermatological hospital in Italy: a questionnaire evaluating the decision-making process and treatment knowledge was self-completed by 231 consecutive psoriasis patients after routine clinical practice and by a second sample of 171 patients exposed to a decision-board. In routine clinical practice 67.9% of patients wanted to be involved in decision-making, 28.4% wanted to leave decisions entirely to the doctor and 3.7% preferred making decisions alone. 17.9% and 25.3% of the control and decision-board group had good knowledge. At multivariate analysis good knowledge increased the likelihood of preferring an active role (risk ratio (RR) = 2.21; 95% confidence interval (CI) 1.3-3.9; p = 0.006). The decision-board only marginally improved patient knowledge and doctor-patient communication. In conclusion, large proportions of psoriasis patients want to participate in decision-making, but insufficient patient knowledge can represent a barrier.

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