​Supervisors: Dr Ashlea Kemp (RAL) + Prof Jocelyn Monroe (Oxford/RAL) 

The Standard Model of particle physics is a remarkably successful theory in describing matter and its interactions, yet it falls short in explaining the full picture of our Universe— notably the mysterious, non-luminous mass component called “dark matter”. The nature of dark matter (DM), yet to be directly observed, is at the forefront of physics research today. Direct detection experiments, which seek to observe rare interactions of DM particles with atoms in terrestrial detectors, require low energy thresholds and extremely low background levels. These challenges are strong drivers for innovative advances in particle detectors, including the use of quantum technologies. To date, most direct detection searches for particle DM have focused on Weakly Interacting Massive Particle (WIMP) DM candidates; the lack of observation of WIMPs has prompted an explosion of interest in DM models predicting candidates with lower mass than WIMPs. This PhD project bridges the domains of quantum technologies and low-mass DM direct detection.  

  
This studentship will focus on the challenge of rejecting cosmogenic and radiation backgrounds to low-mass DM searches, using quantum technology at laboratory bench scale in the QUEST-DMC project, and in the largest direct detection experiment built to date, DarkSide-20k. QUEST-DMC is a unique collaboration of ultra-low temperature (ULT) and particle physicists within the Quantum Technologies for Fundamental Physics programme, and is projected to reach world-leading sensitivity to sub-GeV DM interactions using a superfluid helium-3 target [1]. DarkSide-20k is a flagship international experiment constructing a 51-tonne detector at LNGS with a liquid argon target and will reach more than an order of magnitude increase in the sensitivity over current searches low-mass DM [2].  A crucial aspect of both projects is to veto, i.e. identify and reject, background interactions coming from outside the DM target detector volume. This is done using dedicated veto sub-detector systems which surround the DM target; interactions in the DM target which have coincident activity in the veto systems can be cleanly identified as not originating from DM.  
 
The project will involve developing hardware on-site at the Rutherford Appleton Laboratory (RAL) towards a cosmogenic and internal radioactivity veto system to be deployed within a QUEST-DMC ULT cryostat, where the student will gain first-hand experience with cryogenic photodetection and operating dilution refrigerators. The student will also gain experience of a large, international project through commissioning and calibration of the large-scale cosmogenic veto in DarkSide-20k on-site at LNGS during their long-term attachment. The student will contribute to developing analysis software to reject external backgrounds, combining DM target volume and veto sub-detector system information, in low-mass DM searches testing a range of new physics models beyond the traditional WIMP paradigm, with the prospect of a combined analysis across QUEST-DMC and DarkSide-20k datasets.  
 
The research will take place jointly at RAL and University of Oxford, conveniently located 25 mins from each other by car and connected by bus. We welcome applications from individuals of all backgrounds and are committed to promoting diversity in the field of physics.​