First results on Electronic Recoils from the XENONnT Dark Matter Experiment at LNGS

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Stefano Longo
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Speaker: Marco Selvi - INFN Bologna (Responsabile Nazionale INFN di XENON)

Chair: Carlo Bucci - INFN-LNGS (Responsabile Divisione Ricerca LNGS)

We report on a blind analysis of low-energy electronic-recoil data from the first science run of the XENONnT dark matter experiment, installed and operated at the INFN Laboratori Nazionali del Gran Sasso. Novel subsystems and the increased 5.9 tonne liquid xenon target reduced the background in the (1, 30) keV search region to (16.1 \pm 1.3) events/(t yr keV), the lowest ever achieved in a dark matter detector, and ∼5 times lower than its predecessor XENON1T.
With an exposure of 1.16 tonne-years, we observe no excess above backgrounds and set new stringent limits on solar axions, an enhanced neutrino magnetic moment, and bosonic dark matter. The excess around ∼ 2.3 keV presented by XENON1T is excluded at ∼ 4σ statistical significance. We speculate that trace amounts of tritium may have contributed to the observed XENON1T excess and that the rigorous preventive measures in XENONnT removed this potential background source.