The XENON1T Dark Matter Search Experiment

TL;DR

Direct detection of WIMPs is challenged by extremely rare interactions and backgrounds. The paper presents Xenon1T, a 2.2 t LXe dual-phase TPC with ~1.1 t fiducial mass, designed to achieve unprecedented sensitivity through low backgrounds and high light yield. The projected spin-independent WIMP-nucleon cross-section reach is about $2\times10^{-47}$ cm$^2$ in 2 years, with the potential to observe on the order of 100 events for $\sigma_{\mathrm{SI}} \sim 10^{-45}$ cm$^2$ at $m_\chi \approx 100$ GeV/$c^2$, enabling strong constraints on SUSY WIMP scenarios. This work highlights the significance of ton-scale LXe detectors for probing electroweak-scale dark matter and complements indirect searches and collider experiments.

Abstract

The worldwide race towards direct dark matter detection in the form of Weakly Interacting Massive Particles (WIMPs) has been dramatically accelerated by the remarkable progress and evolution of liquid xenon time projection chambers (LXeTPCs). With a realistic discovery potential, XENON100 has already reached a sensitivity of $7\times10^{-45}\,\n{cm}^2$, and continues to accrue data at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy towards its ultimate sensitivity reach at the $σ_{\n{SI}}\sim 2\times10^{-45}\,\n{cm}^2$ level for the spin-independent WIMP-nucleon cross-section. To fully explore the favoured parameter space for WIMP dark matter in search of a first robust and statistically significant discovery, or to confirm any hint of a signal from \Xehund, the next phase of the XENON program will be a detector at the ton scale - XENON1T. The XENON1T detector, based on 2.2 ton of LXe viewed by low radioactivity photomultiplier tubes and housed in a water Cherenkov muon veto at LNGS, is presented. With an experimental aim of probing WIMP interaction cross-sections above of order $σ_{\n{SI}}\sim 2\times10^{-47}\,\n{cm}^2$ within 2 years of operation, XENON1T will provide the sensitivity to probe a particularly favourable region of electroweak physics on a timescale compatible with complementary ground and satellite based indirect searches and with accelerator dark matter searches at the LHC. Indeed, for a $σ_{\n{SI}} \sim 10^{-45}\,\n{cm}^2$ and $100 \,\n{GeV/c^2}$ WIMP mass, XENON1T could detect of order 100 events in this exposure, providing statistics for placing significant constraints on the WIMP mass.

Figures (2)

• Figure 1: Left: Cross sectional drawing of the Xenon1T cryostat containing the PTFE that bounds the active LXe, PMTs and support structures, field shaping rings and wire-mesh electrodes. Right: The cryostat will be suspended at the center of an active water shield. Here the cryostat with only the central pipe is shown in the tank with the external support structure.
• Figure 2: Left:$1\sigma$ uncertainties in determining WIMP mass and $\sigma_{WIMP-N}$ from 2.2 ton-years with Xenon1T. WIMP masses of 20, 50, 100, 200, 500 GeV/c$^{2}$ and $\sigma_{WIMP-N}$ of $10^{-45}\,\mathrm{cm}^{2}$. Right: Achieved and projected limits on $\sigma_{\mathrm{SI}}$ from the Xenon100 and Xenon1T detectors. For comparison, results from a selection of other experiments are shown along with the most likely parameter space for a detection as predicted by the Constrained Minimal Supersymmetric Extension of the Standard Model Trotta:2008Buchmueller:2011.