The LUX-ZEPLIN (LZ) Dark Matter Search

Lead Research Organisation: University College London
Department Name: Physics and Astronomy

Abstract

Direct dark matter experiments search for the extremely rare and very faint collisions expected to occur between the cold dark matter particles that are believed to permeate our galaxy and the nuclei of atoms in the active medium of a radiation detector. Weakly Interactive Massive Particles, or WIMPs, are hypothetical elementary particles weighing as little as a few protons or as much as several heavy nuclei; besides gravity, they would interact by the weak nuclear force, thereby providing a mechanics for their possible detection. The motivation to search for WIMP dark matter is strong, with theories that attempt to explain what lies beyond the Standard Model of Particle Physics providing very good candidates.

The LUX-ZEPLIN (LZ) experiment will deploy a 7-tonne liquid xenon WIMP detector at the 4850-foot level of the Sanford Underground Research Facility (SURF) after a 3-year construction phase. In this most quiet of environments, shielded from cosmic rays and local backgrounds, LZ will then operate for at least 3 years to hopefully find a handful of tell-tale signs of WIMP interactions. LZ will be so sensitive that it will be limited only by backgrounds from astrophysical neutrinos, which provide a fundamental limit to these searches. However, before neutrinos set in, this experiment has the potential to finally shed light on the nature of dark matter.

Planned Impact

This project will address the fundamental nature of the dark matter in the universe, of great importance to particle physics, astrophysics and cosmology. Our science output will directly impact these fields by constraining models of physics beyond the Standard Model and structure formation and evolution in the universe.

The technologies we are developing find wider and immediate benefit to other areas of physics within the STFC remit, notably long baseline neutrino oscillation experiments and neutrino-less double beta decay (0vBB) searches. Construction and operation of a multi-tonne noble gas time projection chamber impacts the UK and international neutrino physics communities seeking to develop detectors based on similar principles and technology. Challenges such as high voltage delivery, light collection, sensor readout, purification and electron transport, and long-term stability are all paralleled for proposed experiments such as LBNF, which could also be located at SURF, and with significant UK involvement. Similarly, LZ will develop and employ leading ultra-low background techniques to construct an instrument capable of detecting the rarest particle interactions. Experiments searching for rare 0vBB decay have similar requirements on stringent radio purity. The UK 0vBB community and their international partners will benefit from our material screening instrument development and radiation detection techniques.

Our outputs developing low-background material screening technology will find further application in a diverse range of applications outside of physics. Mass-spectrometry instrumentation capable of detecting trace contaminants at parts-per-trillion levels in small samples provides unprecedented sensitivity for food safety, pharmaceutical, environmental, forensic and clinical research. Commercial service providers are limited in their capability due to regular exposure to high concentrations of impurities in their samples. We will validate our system against food safety and pharmaceutical standards from mid-2017. Demonstration of successful screening for toxicity in spiked samples, beginning with titanium dioxide nanoparticles, has the potential for improving safety standards and impacting UK health.

We will also investigate feasibility of measuring impact of uranium and thorium in silicon electronics chips from 2017. The alpha decays from U and Th progeny cause 'Single Event Effects' resulting in faults in integrated circuits; a problem that is increasingly significant as chips become smaller, and an area of active research. Coupled to our underground ultra-low background gamma spectroscopy capability, we can uniquely provide measures of the full U and Th chains, at sub mBq/kg sensitivity, accounting for the complete alpha particle emission rates. Pre-screening Si and other construction materials with both mass spectrometry and gamma spectroscopy will allow manufacturers to increase reliability of their components and foster greater economic competitiveness of UK industry.

Our research provides training for students and staff in a wide range of specialist skills that are readily transferrable to commercial, financial and industrial sectors. Radiation detection technology and techniques are applicable to medical imaging and defence, particularly screening for special nuclear material. Data processing, analysis, statistical methods, programming, and Monte Carlo simulations are regularly employed in the banking and investment sectors. Construction of vacuum systems, gas recirculation and purification plants, photosensors and many other systems in LZ provide valuable engineering skills, as does project management training.

Finally, given the readily accessible nature of the topic of dark matter and deep underground operation, our research has always captured the public's imagination, providing significant outreach and engagement opportunity for dissemination of knowledge.

Publications

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Akerib D (2016) Tritium calibration of the LUX dark matter experiment in Physical Review D

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Akerib DS (2017) Results from a Search for Dark Matter in the Complete LUX Exposure. in Physical review letters

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Carmona-Benitez M (2016) First Results of the LUX Dark Matter Experiment in Nuclear and Particle Physics Proceedings

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Dobson J (2018) Ultra-low background mass spectrometry for rare-event searches in Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

 
Title Laboratory of Dark Matters 
Description An exhibition of new artworks by 10 artists responding to dark matter research installed at Cleveland Ironstone Mining Museum for 6 weeks. Research information was provided in the gallery in the form of A4 sheets and A3 folders with sections on dark matter research, Boulby Underground Laboratory, Scientist profiles and the artworks on display. Four Cloud Chamber workshops and two Phosphorescence Workshops with hands-on creative activities and demonstrations were run by the artists. Gallery tours, Talks and Q&A with scientists and artists, a Private View event for local VIP's and museum community and an open day event with dark matter themed games, quizzes and activities that were cross-generational and fun. Participating artists: Amy Gear, Daniel Clark, Elizabeth Murton, Kate Fahey, Luci Eldridge, Melanie King, Peter Glasgow, Sarah Gillett, Susan Eyre, Robert Good. 
Type Of Art Artistic/Creative Exhibition 
Year Produced 2017 
Impact Opening people's eyes to the mysteries of the universe and the pleasure of discovery by offering a unique experience in a hard to reach area. As a result of the project artists have been invited to speak at events such as The Royal Society discussion Cultures Combined: Art and Science, June 2017; the Institute of Physics INTERACT Conference Birmingham 2017; to curate IAmSciArt twitter feed November 2017; to show artwork at the European Week of Astronomy and Space Science in Liverpool April 2018; to participate in Deptford X exhibition and join artists collective by cloud chamber workshop participants at Guest Projects; write project Blog for IOP Aug 2017; collaborate on Dark Matter Day public discussion/reading group with UCL High Energy Physics PhD students October 2017; invited by Yinka Shonibare to join judging panel at Guest Projects to review and vote on new proposals for 2018; approached by The Royal Holloway University to collaborate on an event for Dark Matter Day 2018. Courtyard billboard artwork 'How To Know The Starry Heavens' at Cleveland Ironstone Mining Museum has remained up so the work is being seen for a much longer duration than originally planned. Cloud chamber workshop model copied for a school programme by workshop participant. Cleveland Ironstone Mining Museum have been awarded Heritage Lottery Funding for a major expansion project and they believe Laboratory of Dark Matters helped secure this as the awarding body took an interest in the exhibition and events which showed diversity and new audience engagement. Ours was the first contemporary art exhibition they had ever hosted but now the museum will have a dedicated gallery in the new build with new ties to local artists and a programme of exhibitions. A project website with links to further information. A publication giving an overview of dark matter, Boulby Underground Laboratory, the artists responses and artworks. Contacts made for future art/science collaborations. Artists have learnt a lot about dark matter and related theories that will feed their practices. Workshop leaders have tried and tested workshop plans they can offer elsewhere. For some it was learning a complete new set of skills running a workshop and this has given confidence to do more projects of this sort. We have gained valuable new tools in the communication of ideas across disciplines and skills in project management, planning, negotiating & collaborating with diverse and remote institutions. Relationships of support & co-operation have been built between artists and scientists that will be the foundation for future projects. 
URL http://www.laboratoryofdarkmatters.com
 
Title Perspectives On The Unknown 
Description Perspectives on the Unknown is a short documentary film that investigates a scientific discovery known as dark matter and dark energy, which fills up over 95% of the Universe and yet remains as the unknown. The film tries to present different perspectives on this invisible matter by questioning how scientists deal with this mysterious matter, and how artists interpret this unknown. The film features two artists, Alison Gill and Julie Mecoli, with a physics academic, Dr. Chamkaur Ghag from department Physics and Astronomy at the University College London. This project is a collaborative project with Roger Stabbins and Thomas Deacon. 
Type Of Art Film/Video/Animation 
Year Produced 2015 
Impact This work has led to further enquiries from students in the arts, and organisation of a visit tot the Boulby Underground Laboratory in 2016 where several national artists will group and develop proposals for further collaborative work. The intention is that this would result in a travelling exhibit. 
URL https://vimeo.com/123613759
 
Description Chair of STFC's Particle Astrophysics Advisory Panel
Geographic Reach National 
Policy Influence Type Participation in a advisory committee
 
Description Membership of STFC Science Board's Particle Astrophysics Advisory Panel
Geographic Reach National 
Policy Influence Type Participation in a advisory committee
URL http://www.stfc.ac.uk/about-us/how-we-are-governed/advisory-boards-panels-committees/particle-astrop...
 
Description Impact Acceleration Award
Amount £5,000 (GBP)
Funding ID ST/M003981/1 
Organisation Science and Technologies Facilities Council (STFC) 
Sector Academic/University
Country United Kingdom
Start 10/2015 
End 12/2015
 
Description International Exchanges Award
Amount £11,029 (GBP)
Funding ID IE141517 
Organisation The Royal Society 
Sector Academic/University
Country United Kingdom
Start 03/2015 
End 02/2017
 
Title Development of lead shields 
Description In partnership with UK industry (Lead Shield Engineering) we have developed new designs for low background radiation shields for use with gamma spectroscopy detectors. 
Type Of Material Improvements to research infrastructure 
Year Produced 2015 
Provided To Others? Yes  
Impact These designs have been realised with lead and copper shields manufactured by Lead Shield Engineering UK for the Boulby Underground Laboratory, the AWE, and others. 
URL http://www.lead-shield.co.uk/
 
Title Trace radioactivity analyses with ICP-MS 
Description Development of methods for trace uranium and thorium radioactivity analyses with ICP-MS using microwave digestion 
Type Of Material Technology assay or reagent 
Year Produced 2016 
Provided To Others? Yes  
Impact We have been able to assay materials to levels of less than 10 ppt (g/g) for uranium-238 and thorium-232 
 
Title Trace radioactivity measurements 
Description Improvements to trace radioactivity measurements in material samples using underground gamma spectroscopy and surface mass spectrometry. 
Type Of Material Improvements to research infrastructure 
Year Produced 2015 
Provided To Others? Yes  
Impact We have provided low level radioactivity measurements for rare event search experiments with UK involvement but also to industry; in particular SSI, and Photek Ltd for the enhancement of their products supplied commercially to UK and international consumers. 
URL http://www.boulby.stfc.ac.uk/Boulby/Projects/39343.aspx
 
Description LUX-ZEPLIN 
Organisation Lyngby-Taarbæk Municipality
PI Contribution I am the co-lead of the LZ 'Background and Screening' Work Package (WBS1.10), one of 11 in the international project, and lead for the equivalent Work Package (WP4) in the UK project. These contain tasks related to the radio-assay of all materials for construction of the instrument to meet low-background requirements unprecedented in the field to-date, and characterization of the experiments radiation field from materials and the environment to provide accurate input for the background model. These are crucial tasks necessary for LZ to achieve its science reach in terms of Dark Matter sensitivity, and to assess any potential signal in case of discovery. In addition to overall leadership and management of these Work Packages, UCL is specifically responsible for delivery of approximately half of all project radio-assays together with radio-content characterization and modeling. This is performed with state-of-the-art technologies and infrastructure I have been developing in the UK since 2012.
Collaborator Contribution All other activities in this international collaboration, from design through to construction.
Impact Construction of the LZ dark matter experiment
Start Year 2012
 
Description Event Horizon Cafe Scientifique 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Undergraduate students
Results and Impact 30 people attended a Cafe Scientifique event organised by UCL undergraduate students where I talked about the search for Dark Matter in our Universe. Impact that has arisen since includes requests for more information on how to conduct further studies or apply for PhD and postgraduate positions in the field of Dark Matter and particle physics in general.
Year(s) Of Engagement Activity 2015
URL https://www.facebook.com/events/197495787252785/
 
Description Article in Cosmos magazine 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Featured in a Cosmos Magazine article about the search for Dark Matter.
Year(s) Of Engagement Activity 2015
URL https://cosmosmagazine.com/physical-sciences/ghost-traps-hunt-dark-matter
 
Description BBC Today programme feature 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Radio feature discussing UK particle physics and involvement in 'Beyond Standard Model' experiments including Dark Matter searches.
Year(s) Of Engagement Activity 2013
URL http://www.bbc.co.uk/programmes/b03kpnjl
 
Description Forbes magazine article 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact 5000 views of this article discussing Dark Matter experiments with UK involvement, where I discuss the implications of new results. This article led to changes in opinion of the readers as documented by the comments on the website, and further enquiries.
Year(s) Of Engagement Activity 2013
URL http://www.forbes.com/sites/bridaineparnell/2013/11/07/why-the-lux-results-matter-to-dark-matter-and...
 
Description IOP Physics World article 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Article highlighting the selection of the next generation of experiments in the search for Dark Matter, including LZ.
Year(s) Of Engagement Activity 2014
URL http://physicsworld.com/cws/article/news/2014/jul/15/dark-matter-searches-get-us-government-approval
 
Description IOP Physics World article 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Article in Physics World magazine about underground science including Dark Matter searches. This article highlighted activities at the UK's Boulby Underground Laboratory.
Year(s) Of Engagement Activity 2015
URL http://physicsworld.com/cws/article/indepth/2015/may/07/subterranean-science
 
Description Light and Dark TV series 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact This was a major BBC production broadcast on TV in two-parts, hosted by Prof. Jim Al-Khalili. It featured a section on Dark Matter where I discussed underground experimental techniques.
Year(s) Of Engagement Activity 2013
URL http://www.bbc.co.uk/programmes/b03jrxhv
 
Description Naked Scientists Radio and Podcast feature 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Radio and Podcast feature by the Naked Scientists discussing Dark Matter searches. This feature led to several further media enquiries and questions from the general public.
Year(s) Of Engagement Activity 2015
URL http://www.thenakedscientists.com/HTML/podcasts/naked-scientists/show/20150602/
 
Description New Scientist Public Event 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact 270 members of the general public attended a Particle Physics Experts Masterclass organised by New Scientist. I was one of the 5 experts, presenting Dark Matter including the LZ experiment, and I was a member of the panel for a Q&A session. There was significant interest during the ticketed event (£150 per person), and outcomes that have arisen since include contact from schools and students regarding Dark Matter for their school projects, and contact from the media.
Year(s) Of Engagement Activity 2016
URL http://www.eventbrite.co.uk/e/instant-expert-mysteries-of-particle-physics-tickets-19713709235?aff=n...
 
Description Public Lecture at Second Home 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Industry/Business
Results and Impact Approximately 70 people that work at or operate from Second Home, London, attended a talk about Dark Matter that focused on technologies. Second Home houses numerous technology firms and businesses and this talk led to several questions about potential socioeconomic impact of particle physics and Dark Matter experiments, and potential areas for collaborative research and spin-offs. It has also led to arrangement of a trip to Boulby Underground Laboratory in 2016, where I will host 10 artists from across the UK on an underground tour of the science facility.
Year(s) Of Engagement Activity 2015
URL https://www.facebook.com/events/1498288067129210/
 
Description Radio 5 Live feature 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Dark Matter feature on Radio 5 live, highlighting UK research. This feature led to enquiries from the general public and other media outlets.
Year(s) Of Engagement Activity 2015
URL http://www.bbc.co.uk/programmes/b043wvt9
 
Description Radio feature on Newsdrive 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Interview on BBC Newsdrive discussing UK involvement in international Dark Matter search experiments.
Year(s) Of Engagement Activity 2014
URL http://www.bbc.co.uk/programmes/b03zdylq
 
Description School Visit (Newham Collegiate College, London) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact Particle physics seminar focussing on searched for beyond the standard model physics, particularly for dark matter signatures. Approximately 40 students attended, and there was considerable interest afterwards with questions, discussion, and follow up emails to me.
Year(s) Of Engagement Activity 2017