Lunedì 11 novembre ore 14:00, Aula D - Dipartimento di Fisica dell'Università degli Studi di Trieste
In programma lunedì 11 novembre presso l'Aula D del Dipartimento di Fisica dell'Università degli Studi di Trieste, il seminario dal titolo "The DarkSide-20k experiment for direct search of Dark Matter at LNGS, status and perspectives". Ospite il prof. Sandro De Cecco, Università degli Studi di Roma "La Sapienza" e INFN Roma.
Titolo del seminario: The DarkSide-20k experiment for direct search of Dark Matter at LNGS, status and perspectives
Sommario: The nature of dark matter is a central question in fundamental physics. The Weakly Interacting Massive Particles paradigm fulfills the requirements for a dark matter candidate, as supported by both cosmology and particle physics. WIMPs are investigated with a variety of techniques, which allowed to exclude a large phase-space region, but no experiment reached the irreducible background due to coherent elastic scattering of solar and atmospheric neutrinos on detector targets. Dual-phase noble-liquid time projection chambers (TPCs) are the current leading technology. Their main advantage is simultaneous access to scintillation and ionization signals, enabling event-topology reconstruction and discrimination between electrons and WIMP-like or nuclear recoils. A number of TPCs in the Xenon1T, PandaX, and LUX experiments successfully profit from liquid xenon targets, which guarantee excellent radio-purity and high stopping power. Liquid argon (LAr) has similar properties, and offers unique discrimination power (>108) between nuclear and electron recoils, exploiting the scintillation pulse shape. However, it suffers from intrinsic contamination of cosmogenic 39Ar, a problem recently solved in the DarkSide experiment with the use of depleted argon of underground origin (UAr) through the URANIA plant and purification by cryogenic distillation with the ARIA project. DarkSide is a multistage program, begun in 2010 with DarkSide-10 (DS-10), a 10 kg liquid-argon prototype followed by DarkSide-50 (DS-50), with 50 kg target mass, installed underground at LNGS within an active neutron veto based on boron-loaded organic scintillator, located in turn inside a 1000-ton water-Cherenkov muon veto. Data acquisition started in late 2013, with argon extracted from atmosphere (AAr), naturally exposed to cosmic rays, and continues in 2025 with a depleted argon target whose residual contamination is measured to be about 1400 times lower than in AAr. DS-50 demonstrated the potential of LAr TPCs operating with UAr: after a ~20 ton-days exposure, the search achieved a null result with zero reducible background. The future generation of multi-ton LAr detectors is designed to be capable of fully background-free dark matter searches, in real discovery mode. Building on the DS-50 success, the four world-leading argon projects (ArDM at LSC, DS-50 at LNGS, DEAP-3600, and MiniCLEAN at SNOLab) joined forces in the Global Argon Dark Matter Collaboration unified program for the next generation experiment. This will be the DarkSide-20k, a dual-phase LAr TPC with 20 ton fiducial mass and 50 tons instrumented target mass of low radioactivity argon. DS-20k is highly innovative: the TPC will be immersed in a 600 ton liquid AAr bath within a membrane proto-DUNE-like cryostat, a solution that allows to host the entire TPC in an ultra-pure acrylic vessel immersed in ~100 tons of low radioactivity UAr separated from the AAr bath by a radio-pure SS vessel. The inner detector will be equipped with ~15~m2 of cryogenic silicon photomultipliers, characterized by high radiopurity, very high (40%) photon-detection efficiency, low noise (0.1-1 Hz/mm2), and high single-electron resolution. UAr instrumented with silicon photomultipliers surround the detector for active neutron veto. Particular attention is given to the extreme radio-purity of the materials. DarkSide-20k is expected to be free of any instrumental background for exposures of 200 tonne per year attaining WIMP-nucleon cross-section exclusion sensitivities of 7 x 10^-48 cm^2 for a WIMP mass of 1 TeV. The construction has now started with commissioning foreseen for late 2026. The talk describes the status of Darkside-20k development and construction along with an overview of recent dark-matter limits by the predecessor experiment DarkSide-50, in particular of a revised low-mass dark matter WIMPs search that includes dark-matter-nucleon interactions via the Migdal effect. It also discuss DarkSide-20k perspectives in light WIMP searches that will allow to improve the DS-50 limit by more than one order of magnitude in less than one year of operation.
Relatori: Sandro De Cecco (Università degli Studi di Roma "La Sapienza" e INFN Roma) e Diego Tonelli (INFN Trieste)
Sede e orario: Aula D del Dipartimento di Fisica dell'Università degli studi di Trieste, ore 14:00
Locandina pdf
Evento a cura del dott. Diego Tonelli diego.tonelli@cern.ch
