Projected WIMP sensitivity of the LUX-ZEPLIN (LZ) dark matter experiment

TL;DR

The paper projects the sensitivity of the LUX-ZEPLIN experiment in detecting WIMPs, showing it can significantly improve current limits and potentially discover dark matter particles within a planned 1000-day run.

Contribution

It provides the first detailed sensitivity projections for the LZ experiment based on current background estimates and detector simulations.

Findings

Projected exclusion limit for spin-independent WIMP-nucleon cross section at 1.4e-48 cm^2

Expected discovery potential below recent experimental limits

Sensitivity estimates for spin-dependent WIMP-neutron and proton scattering

Abstract

LUX-ZEPLIN (LZ) is a next generation dark matter direct detection experiment that will operate 4850 feet underground at the Sanford Underground Research Facility (SURF) in Lead, South Dakota, USA. Using a two-phase xenon detector with an active mass of 7~tonnes, LZ will search primarily for low-energy interactions with Weakly Interacting Massive Particles (WIMPs), which are hypothesized to make up the dark matter in our galactic halo. In this paper, the projected WIMP sensitivity of LZ is presented based on the latest background estimates and simulations of the detector. For a 1000~live day run using a 5.6~tonne fiducial mass, LZ is projected to exclude at 90\% confidence level spin-independent WIMP-nucleon cross sections above $1.4 \times 10^{-48}$~cm$^{2}$ for a 40~$\mathrm{GeV}/c^{2}$ mass WIMP. Additionally, a $5\sigma$ discovery potential is projected reaching cross sections below the exclusion limits of recent experiments. For spin-dependent WIMP-neutron(-proton) scattering, a sensitivity of $2.3 \times 10^{-43}$~cm$^{2}$ ($7.1 \times 10^{-42}$~cm$^{2}$) for a 40~$\mathrm{GeV}/c^{2}$ mass WIMP is expected. With underground installation well underway, LZ is on track for commissioning at SURF in 2020.