We report the first dark matter search results from XENON1T, a ∼2000 kg dual-phase xenon time projection chamber in operation at the Laboratori Nazionali del Gran Sasso in Italy, the first ton-scale detector of this kind.
The blinded search used 34.2 live days of data acquired between November 2016 and January 2017. Inside the (1042±12) kg fiducial mass and in the [5, 40] keV_nr energy range of interest for WIMP dark matter searches, the electronic recoil background was (1.93±0.25)×10⁻⁴ events/(kg × day × keV_ee), the lowest ever achieved in a dark matter detector.
A profile likelihood analysis shows that the data is consistent with the background-only hypothesis. We derive the most stringent exclusion limits on the spin-independent WIMP-nucleon interaction cross section for WIMP masses above 10 GeV/c², with a minimum of 7.7 ×10⁻⁴⁷ cm² for 35-GeV/c² WIMPs at 90% confidence level.

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Marco Selvi
INFN Bologna
http://www.bo.infn.it/~selvi/