LZ: Searching for Dark Matter

The latest estimates show that the total energy balance of the Universe has contributions from ordinary matter (4.9%), Dark Matter (26.8%) and Dark Energy (68.3%). The two latest contributions require new physics models to explain their nature. Measurements are consistent with Dark Matter particles interacting weakly and having density of about 0.3 GeV/cm3 near the Earth. LUX-ZEPLIN (LZ) experiment searches for Dark Matter using a Time Projection Chamber (TPC) containing 7 tonnes of liquefied xenon as a target material. LZ is expected to achieve the best sensitivity for Dark Matter particles with masses from 10GeV to 10TeV. The detector is based in the former Homestake gold mine (South Dakota, USA) at the depth of about 1 mile. Though the rocks protect the detector from cosmic radiation, it has a dedicated active veto system protecting from very rare remaining cosmic muons as well as from external and internal radiation. Outer detector surrounding the TPC is a part of this veto system. The outer detector consists of approximately 17 tonnes of gadolinium-loaded liquid scintillator confined to 10 acrylic tanks surrounding the cryostat and 228,000 litres of water as the outermost layer. It is monitored by 120 inward-facing 8-inch photomultiplier tubes. An optical calibration system has been designed and built by our group to calibrate and monitor these photomultiplier tubes and light transmission in the outer detector. This will allow the veto system to reach its required efficiency and thus ensure that LUX-ZEPLIN meets its target sensitivity.

The Liverpool Dark Matter group joined the LZ project in 2014. In addition to the optical calibration system the group developed data analysis and data quality monitoring frameworks, software for outer detector calibration and visualisation. Group members actively participated in installation of the LZ detector at SURF. The group leads estimates of external laboratory background contributions to the main physics analyses. The group also contributed to LUX physics analyses, in particular, to Effective Field Theory and Inelastic Dark Matter interpretations of LUX results.

Simultaneously, the Liverpool LZ group is involved into the Xenon Futures R&D project which aims to develop a future liquid xenon Global Rare Event Observatory. The expected target mass of 50-100 tonnes of liquid xenon will allow to improve the sensitivity by an order of magnitude. The Liverpool group is responsible for development of interconnects for photosensors in the future detector.

Google view of SURF (120MB!)


NamePictureRoleLZ yearsWhere next?
Sergey Bundin Sergey Burdin PI 2014-present  
Joachim Rose Joachim Rose Co-I 2014-2016 SNO+ Liverpool Faculty
Carl Gwilliam Dr Carl Gwilliam Post-doc 2017-2020 ATLAS Liverpool Faculty
Will Turner Post-doc 2018-2022 The Future Forest Company
Billy Boxer   PhD student 2016-2020 UC Davis Post-doc
Alice Hamer (Baxter)   PhD student 2017-2022 RHUL/Edinburgh Post-doc
Ewan Fraser   PhD student 2018-present  
Harvey Birch   MSc student 2018-2020 University Michigan PhD
Sam Woodford   PhD student 2020-present  
Sam Powell Sam Powell Engineer 2015-2019 University of Liverpool PhD
Ash Greenall Ashley Greenall Engineer 2016-present  
Peter Sutcliffe Engineer 2015-present  
Balint Bogdan   Engineer 2021-present