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Experimental Particle and Astro-Particle Physics Seminar
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Europe/Zurich
Description
Abstract: The NEXT experiment aims at the sensitive search of the neutrinoless double beta decay ($\beta\beta0\nu$) in \Xe{136}, using high-pressure gas electroluminescent time projection chambers. The NEXT-White detector, a radiopure demonstrator operated in the LSC, was exploited between 2015 and 2021 in order to implement the first searches with this technology. Combining \Xe{136}-enriched and \Xe{136}-depleted data, background-model-dependent and novel direct background subtraction approaches have been used to derive measurements of the two-neutrino mode of the $\beta\beta$ decay, as well as limits to the $\beta\beta0\nu$ process. With a fiducial mass of only 3.50$\pm$0.01 kg of \Xe{136}-enriched xenon, 90\% C.L. lower limits have been found in the \Tnonu$>5.5\times10^{23}-1.3\times10^{24}$ yr range, depending on the analysis method. After the decommissioning of NEXT-White, the NEXT-100 detector, holding up to $\sim$100 kg of Xe, has started operation in 2024 at the LSC. Following a successful commissioning stage, the detector is currently being calibrated to perform a first background measurement. With an expected background index below 5$\times$10$^{-4}$ counts/keV/kg/year, this detector will reach a sensitivity of 6$\times$10$^{25}$ yr after 3 years of data taking. NEXT-100 will also set the grounds for the construction of a ton-scale detector, NEXT-HD, boosting the sensitivity above 10$^{27}$ yr. In paralel, an extensive R\&D line is being conducted to equip NEXT-HD with Ba-tagging capabilities, so a truly background-free experiment can be eventually implemented. The results and current stauts of the NEXT roadmap will be presented, in the context of the worldwide efforts to demonstrate that neutrinos are Majorana fermions.