THE LUX-ZEPLIN (LZ) DARK MATTER SEARCH

Lead Research Organisation: University of Liverpool
Department Name: Physics

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-pertrillion
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.
 
Description FPGA and pulser boards produce optical pulses with required intensity 100s - 100000s photons per pulse and required width (below 20ns at the end of 21m fibre). The photodiode board monitors these light pulses and communicates with either Arduino or the FPGA board.
All hardware for Optical Calibration System have been produced and tested. It is ready to be sent to SURF for installation.
Exploitation Route The short light pulses could be used for calibration of the optical systems and sensors. 8-channel optical pulser board could generate pulses which are shifted by 70ps or longer delays between channels.
Sectors Education,Electronics

 
Description GTA Studentship
Amount £35,000 (GBP)
Organisation University of Liverpool 
Sector Academic/University
Country United Kingdom
Start 10/2016 
End 03/2020
 
Description PPGP
Amount £153,875 (GBP)
Funding ID ST/M003639/1 
Organisation Science and Technologies Facilities Council (STFC) 
Sector Academic/University
Country United Kingdom
Start 04/2018 
End 09/2019
 
Title Integrated system for optical pulses 
Description An FPGA board has been integrated with the LED pulser and photodiode boards to produce and monitor short (~ns) optical pulses. There are 8 channels on the board and they could be delayed by approximately 70ps with respect to each other. There are photodiodes on the board allowing control and monitoring of integrated light from each channel. 
Type Of Material Improvements to research infrastructure 
Year Produced 2018 
Provided To Others? Yes  
Impact This optical pulse generation system will be used for the optical calibration of the LZ Outer Detector. The same system will be used for Super-K and as a prototype for Hyper-K optical calibration. Flexibility and integrated control allows using this board for other purposes like stroboscopic photography. 
 
Title 8-channel photodiode board 
Description An 8-channel photodiode board for integrated light control and monitoring has been developed. The board can be used either with Arduino or with dedicated FPGA board. The photodiode board features the 8 Hamamatsu S5971 photodiodes in a housings with SMA connectors. It integrates the light signals, digitizes them and send output to the Arduino or FPGA board. 
Type Of Technology New/Improved Technique/Technology 
Year Produced 2017 
Impact The photodiode board has low noise and allows measurements of optical signals from ~100s to ~1000000s photons per pulse with frequency from 1kHz. Such large dynamic range, low cost and possibility of connecting to Arduino provides opportunity of using the board in wide range of applications. 
 
Title FPGA board for short optical signal generation 
Description An FPGA board has been developed which could be used for generation of short (~ns) optical signals produced by LEDs or LDs. There are 8 channels on the board with the possibility of all the channels working together or separately. The channels could be delayed by approximately 70ps with respect to each other. There are photodiodes on the board allowing control and monitoring of integrated light from each channel. 
Type Of Technology New/Improved Technique/Technology 
Year Produced 2018 
Impact This board will be used for the optical calibration of the LZ Outer Detector. The same board will be used for Super-K and as a prototype for Hyper-K optical calibration. Flexibility and integrated control allows using this board for other purposes like stroboscopic photography. 
 
Title Short 1-5ns LED pulser prototype 
Description A prototype of LED driver board producing short 1-5ns light pulses with the light output in the range of 100-1000000 photons has been developed. 
Type Of Technology New/Improved Technique/Technology 
Year Produced 2015 
Impact The product will be used in development of calibration systems for LZ (Dark Matter) and Hyper-K experiments. 
 
Description Dark Matter Pizza night 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Undergraduate students
Results and Impact 20 students attended Dark Matter Pizza night which was on Oct 31, 2017. I have made a presentation on Dark Matter and LZ experiment in particular. There was a discussion and games after the presentation to show how difficult it is to detect the Dark Matter.
Year(s) Of Engagement Activity 2017
 
Description EuroScience Open Forum 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Dark Matter discussion at the European Scientific Open Forum with audience approximately 100 people where Sergey Burdin was a member of expert panel.
Year(s) Of Engagement Activity 2018
URL https://toulouse2018.esof.eu/en/