Dark Matter Search with the XENON1T Experiment: Background Predictions, Data Analysis and Final Results

The XENON1T experiment is currently the most sensitive in the world for the direct search for dark matter (DM). XENON1T employs a dual-phase (liquid-gas) time projection chamber (TPC) featuring 2.0 t liquid xenon (LXe) target mass. The detector is operated in the underground Laboratori Nazionali del Gran Sasso, in Italy. The search for WIMP, the most popular DMcandidate, conducted with the XENON1T detector for a total exposure of 1.0 t-y is presented in this work. The measured background level amounts to $ 82^{+5}_{-3}\rm{(syst)\pm3\rm{(stat)}}\,(\si{t}\cdot\si{y}\cdot\si{keV})^{-1} $, the lowest ever achieved in a direct detection DM experiment. The profile likelihood analysis of data collected in 278.8 live-days finds no significant excess over background. The statistical inference on the WIMP-nucleon spin-independent cross section sets the world-best exclusion limit for WIMP masses above 8\,GeV/c$ ^2 $, with a minimum of $ 4.1\times10^{-47} $\,cm$ ^2 $ at 30\,GeV/c$ ^2 $ and 90\% confidence level.