LZ First Results (2023): The Hunt for Dark Matter Particles

The LUX-ZEPLIN (LZ) experiment published its first dark matter search in 2023. Watching a 5.5-tonne target of liquid xenon deep underground in South Dakota for 60 days, it saw no sign of dark matter particles, and set the world’s tightest limits on WIMPs, the most popular candidate, heavier than 9 GeV/c².

The question before the paper

Astronomy shows that dark matter outweighs ordinary matter about five to one, from galaxy rotation curves to the Bullet Cluster. If it is made of a new kind of particle, those particles stream through Earth constantly. One leading idea is the WIMP, a weakly interacting massive particle, which would very occasionally bump into an atomic nucleus. Can a detector catch such a collision?

What the paper found

• No signal. The data were consistent with known backgrounds only: no WIMP collisions were found.
• World-leading limits. LZ set the strongest limits for “spin-independent” WIMP-nucleus scattering for WIMP masses above 9 GeV/c² (about 10 times a proton’s mass).
• The sharpest exclusion at 36 GeV/c², ruling out interaction strengths (cross sections) above 9.2 × 10^-48 cm² at 90% confidence.

How they did it

LZ is a dual-phase liquid xenon time projection chamber at the Sanford Underground Research Facility in Lead, South Dakota, nearly a mile underground to block cosmic rays. “Dual-phase” means the xenon is held as a liquid with a thin layer of gas above it; the detector records the faint signals of light and freed electrons produced when a particle strikes a xenon nucleus, and reconstructs where each collision happened. This first search used 60 live days of data and a 5.5-tonne “fiducial” region at the center of the detector, shielded by the outer xenon.

Why it mattered

Direct detection experiments test whether dark matter is a new particle that occasionally interacts with ordinary atoms. Each tighter null result rules out more of the most popular particle candidates. This first run, only 60 days long, already beat every earlier experiment for WIMPs above 9 GeV/c², and it was the starting point for much longer exposures.

What we know now

As of October 2026, LZ has not detected dark matter. In December 2025 it reported a full result from 417 live days, again with no WIMP signal and world-leading sensitivity above 5 GeV/c². In September 2026 the collaboration reported a single event that known backgrounds struggle to explain, at 2.6 sigma, far below the 5 sigma needed for a discovery; the team says it is not claiming to have seen dark matter. LZ aims for more than 1,000 live days by 2028. Researchers at Stanford and SLAC’s KIPAC are among its members.

Who wrote it

The paper is signed by the LZ Collaboration, with individual authors starting with J. Aalbers and D. S. Akerib. It has about 770 citations in Semantic Scholar as of October 2026.

Read the original

LZ Collaboration, Aalbers, J., Akerib, D. S., et al. (2023). “First Dark Matter Search Results from the LUX-ZEPLIN (LZ) Experiment.” Physical Review Letters 131, 041002. doi:10.1103/PhysRevLett.131.041002. Free on arXiv: 2207.03764.