First Dark Matter Search Results from the XENON1T Experiment
  We report the first dark matter search results from XENON1T, a
$\sim$2000-kg-target-mass dual-phase (liquid-gas) xenon time projection chamber
in operation at the Laboratori Nazionali del Gran Sasso in Italy and the first
ton-scale detector of this kind. The blinded search used 34.2 live days of data
acquired between November 2016 and January 2017. Inside the (1042$\pm$12) kg
fiducial mass and in the [5, 40] $\mathrm{keV}_{\mathrm{nr}}$ energy range of
interest for WIMP dark matter searches, the electronic recoil background was
$(1.93 \pm 0.25) \times 10^{-4}$ events/(kg $\times$ day $\times
\mathrm{keV}_{\mathrm{ee}}$), 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/c${}^2$, with a minimum of 7.7 $\times 10^{-47}$ cm${}^2$ for
35-GeV/c${}^2$ WIMPs at 90% confidence level.
