University of Pennsylvania Physics & Astronomy Colloquium

The existence of dark matter is strongly supported by an abundance of astrophysical and cosmological evidence, but has yet to be directly detected. Liquid Xe detectors have been a game changer in the field of dark matter detection, bringing about astonishing improvements in sensitivity over the past decade. The LUX-ZEPLIN (LZ) experiment is a multi-tonne dark matter direct detection experiment operating 4850 feet underground at the Sanford Underground Research Facility in Lead, South Dakota. The experiment utilizes a liquid xenon time projection chamber (TPC) with an active mass of 7 tonnes that will search for the low energy signatures from interactions with Weakly Interacting Massive Particle (WIMP) dark matter in our galactic halo and other rare physics processes. Recently, the LZ collaboration released new results from a combined analysis using data from the 2022 and 2024 science campaigns, amounting to a live exposure of 4.2 tonne-years. No evidence for an excess over expected backgrounds was found across all the test WIMP masses. The resulting limit on the spin-independent WIMP-nucleon cross section is world-leading for masses above 9 GeV/c^2, surpassing previous best limits by about a factor of four. In this talk, I will discuss the evidence for dark matter and present the new results from LZ, report on the experiment's status and discuss the next steps towards a global xenon-based rare-event search observatory.