The stability of a dark matter detector on the timescale of a few years is a key requirement due to the large exposure needed to achieve a competitive sensitivity. It is especially crucial to enable ...the detector to potentially detect any annual event rate modulation, an expected dark matter signature. In this work, we present the performance history of the DarkSide-50 dual-phase argon time projection chamber over its almost three-year low-radioactivity argon run. In particular, we focus on the electroluminescence signal that enables sensitivity to sub-keV energy depositions. The stability of the electroluminescence yield is found to be better than 0.5%. Finally, we show the temporal evolution of the observed event rate around the sub-keV region being consistent to the background prediction.
Dark matter induced event rate in an Earth-based detector is predicted to show an annual modulation as a result of the Earth's orbital motion around the Sun. We searched for this modulation signature ...using the ionization signal of the DarkSide-50 liquid argon time projection chamber. No significant signature compatible with dark matter is observed in the electron recoil equivalent energy range above \(40~{\rm eV_{ee}}\), the lowest threshold ever achieved in such a search.
We present a novel approach for the search of dark matter in the DarkSide-50 experiment, relying on Bayesian Networks. This method incorporates the detector response model into the likelihood ...function, explicitly maintaining the connection with the quantity of interest. No assumptions about the linearity of the problem or the shape of the probability distribution functions are required, and there is no need to morph signal and background spectra as a function of nuisance parameters. By expressing the problem in terms of Bayesian Networks, we have developed an inference algorithm based on a Markov Chain Monte Carlo to calculate the posterior probability. A clever description of the detector response model in terms of parametric matrices allows us to study the impact of systematic variations of any parameter on the final results. Our approach not only provides the desired information on the parameter of interest, but also potential constraints on the response model. Our results are consistent with recent published analyses and further refine the parameters of the detector response model.
We report on the search for dark matter WIMPs in the mass range below 10 GeV/c\(^2\), from the analysis of the entire dataset acquired with a low-radioactivity argon target by the DarkSide-50 ...experiment at LNGS. The new analysis benefits from more accurate calibration of the detector response, improved background model, and better determination of systematic uncertainties, allowing us to accurately model the background rate and spectra down to 0.06 keV\(_{er}\). A 90% C.L. exclusion limit for the spin-independent cross section of 3 GeV/c\(^2\) mass WIMP on nucleons is set at 6\(\times\)10\(^{-43}\) cm\(^2\), about a factor 10 better than the previous DarkSide-50 limit. This analysis extends the exclusion region for spin-independent dark matter interactions below the current experimental constraints in the \(1.2, 3.6\) GeV/c\(^2\) WIMP mass range.
Dark matter elastic scattering off nuclei can result in the excitation and ionization of the recoiling atom through the so-called Migdal effect. The energy deposition from the ionization electron ...adds to the energy deposited by the recoiling nuclear system and allows for the detection of interactions of sub-GeV/c\(^2\) mass dark matter. We present new constraints for sub-GeV/c\(^2\) dark matter using the dual-phase liquid argon time projection chamber of the DarkSide-50 experiment with an exposure of (12306 \(\pm\) 184) kg d. The analysis is based on the ionization signal alone and significantly enhances the sensitivity of DarkSide-50, enabling sensitivity to dark matter with masses down to 40 MeV/c\(^2\). Furthermore, it sets the most stringent upper limit on the spin independent dark matter nucleon cross section for masses below \(3.6\) GeV/c\(^2\).
We present a search for dark matter particles with sub-GeV/\(c^2\) masses whose interactions have final state electrons using the DarkSide-50 experiment's (12306 \(\pm\) 184) kg d low-radioactivity ...liquid argon exposure. By analyzing the ionization signals, we exclude new parameter space for the dark matter-electron cross section \(\bar{\sigma}_e\), the axioelectric coupling constant \(g_{Ae}\), and the dark photon kinetic mixing parameter \(\kappa\). We also set the first dark matter direct-detection constraints on the mixing angle \(\left|U_{e4}\right|^2\) for keV sterile neutrinos.
This paper studies the friction and wear of Hadfield steel single crystals with the normal load/friction force orientations 1‾1‾0/1‾10 and 1‾1‾0/001. Due to the different friction force orientation, ...deformation occurs by twinning in the first case and by slip in the second case. The shear stresses were estimated and correlated with the observed slip band systems. Changes in the orientation of the worn surface were examined by EBSD analysis. TEM studies were performed to investigate the dislocation structure evolution near the worn surface.
•Sliding friction tests were conducted on Hadfield steel single crystals with different crystallographic orientations.•Deformation behavior of the material during sliding and twinning was described.•Reorientation in the region near the worn surface affects the work hardening mechanism of single crystals.•Structural changes in the immediate vicinity of the worn surface were observed.
