Precision measurements of solar neutrinos emitted by specific nuclear reaction chains in the Sun are of great interest for developing an improved understanding of star formation and evolution. Given ...the expected neutrino fluxes and known detection reactions, such measurements require detectors capable of collecting neutrino-electron scattering data in exposures on the order of 1 ktonne-yr, with good energy resolution and extremely low background. Two-phase liquid argon time projection chambers (LAr TPCs) are under development for direct Dark Matter WIMP searches, which possess very large sensitive mass, high scintillation light yield, good energy resolution, and good spatial resolution in all three cartesian directions. While enabling Dark Matter searches with sensitivity extending to the ``neutrino floor'' (given by the rate of nuclear recoil events from solar neutrino coherent scattering), such detectors could also enable precision measurements of solar neutrino fluxes using the neutrino-electron elastic scattering events.
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.
Theophylline is at present one of the standard drugs used for asthma and obstructive respiratory diseases but still presents clinical problems due to its narrow therapeutic range. To provide ...additional studies in this important field, the in vivo bioavailability of Bronchoretard, a theophylline sustained-release preparation, not available at present in Italy, has been compared with that of Diffumal, formulation of large consumption. An isocratic reverse-phase HPLC method to assess the theophylline in plasma is described. The two formulations present good bioequivalence, though Bronchoretard seems to provide little therapeutic advantage.
Finding unequivocal evidence of dark matter interactions in a particle detector is a major objective of physics research. Liquid argon time projection chambers offer a path to probe Weakly ...Interacting Massive Particles scattering cross sections on nucleus down to the so-called neutrino floor, in a mass range from few GeV's to hundredths of TeV's. Based on the successful operation of the DarkSide-50 detector at LNGS, a new and more sensitive experiment, DarkSide-20k, has been designed and is now under construction. A thorough understanding of the DarkSide-50 detector response and, therefore, of all kind of observed events, is essential for an optimal design of the new experiment. In this paper, we report on a particular set of events, which were not used for dark matter searches. Namely, standard two-pulse scintillation-ionization signals accompanied by a small amplitude third pulse, originating from single or few electrons, in a time window of less than a maximum drift time. We compare our findings to those of a recent paper of the LUX Collaboration (D.S.Akerib et al. Phys.Rev.D 102, 092004). Indeed, both experiments observe events related to photoionization of the cathode. From the measured rate of these events, we estimate for the first time the quantum efficiency of the tetraphenyl butadiene deposited on the DarkSide-50 cathode at wavelengths around 128 nm, in liquid argon. Also, both experiments observe events likely related to photoionization of impurities in the liquid. The probability of photoelectron emission per unit length turns out to be one order of magnitude smaller in DarkSide-50 than in LUX. This result, together with the much larger measured electron lifetime, coherently hints toward a lower concentration of contaminants in DarkSide-50 than in LUX.
DarkSide-50 has demonstrated the high potential of dual-phase liquid argon time projection chambers in exploring interactions of WIMPs in the GeV/c\(^2\) mass range. The technique, based on the ...detection of the ionization signal amplified via electroluminescence in the gas phase, allows to explore recoil energies down to the sub-keV range. We report here on the DarkSide-50 measurement of the ionization yield of electronic recoils down to \(\sim\)180~eV\(_{er}\), exploiting \(^{37}\)Ar and \(^{39}\)Ar decays, and extrapolated to a few ionization electrons with the Thomas-Imel box model. Moreover, we present a model-dependent determination of the ionization response to nuclear recoils down to \(\sim\)500~eV\(_{nr}\), the lowest ever achieved in liquid argon, using \textit{in situ} neutron calibration sources and external datasets from neutron beam experiments.
