First Dark Matter Search Results from the LUX-ZEPLIN (LZ) Experiment

TL;DR

The LUX-ZEPLIN experiment conducted its first search for dark matter particles, setting new limits on WIMP interactions with nucleons, and found no evidence of dark matter signals in 60 days of data.

Contribution

This paper presents the initial results from LUX-ZEPLIN, providing the most stringent limits to date on WIMP-nucleon cross sections for masses above 9 GeV/c².

Findings

No excess events observed over background

Set new upper limits on WIMP interaction cross sections

Most stringent limit at 36 GeV/c² for spin-independent scattering

Abstract

The LUX-ZEPLIN experiment is a dark matter detector centered on a dual-phase xenon time projection chamber operating at the Sanford Underground Research Facility in Lead, South Dakota, USA. This Letter reports results from LUX-ZEPLIN's first search for weakly interacting massive particles (WIMPs) with an exposure of 60~live days using a fiducial mass of 5.5 t. A profile-likelihood ratio analysis shows the data to be consistent with a background-only hypothesis, setting new limits on spin-independent WIMP-nucleon, spin-dependent WIMP-neutron, and spin-dependent WIMP-proton cross sections for WIMP masses above 9 GeV/c$^2$. The most stringent limit is set for spin-independent scattering at 36 GeV/c$^2$, rejecting cross sections above 9.2$\times 10^{-48}$ cm$^2$ at the 90% confidence level.