Thesis

Enhancing liquid xenon detectors for future experiments

• Call:

  PT-CERN Call 2022/2

• Academic Year:

  2022

• Domain:

  Astrophysics

• Supervisor:

  Alexandre Lindote

• Co-Supervisor:

  Henrique Araujo

• Institution:

  Universidade de Coimbra

• Host Institution:

  Laboratório de Instrumentação e Física Experimental de Partículas

• Abstract:

  Two-phase (liquid/gas) xenon time projection chambers (TPCs) lead the search for dark matter (DM) particles with masses between ~1 GeV and ~10 TeV typical of new physics at the electroweak scale. This is a well established and scalable technology, having evolved from detectors with a few kg nearly two decades ago to the current 2nd generation (G2) multi-tonne detectors (LZ and XENONnT). Nevertheless, there is broad consensus in the community that a larger (G3) detector is needed to probe the remaining WIMP parameter space down to the irreducible neutrino “fog” and explore other models motivating lighter particles. The XLZD consortium was recently formed by merging members from the XENON, LZ, and DARWIN collaborations, with the goal of designing and performing the required R&D towards such a detector. With 50-100 tonnes of xenon, it will be operating around the end of the decade and will serve as a Global Rare Event Observatory, with leading sensitivity to multiple DM candidates and, given its extremely low background, it will be able to competitively search for other rare physics phenomena – including 0𝝂ββ decay. This project foresees the integration of the student in the XLZD consortium, and an ambitious set of R&D activities to improve the performance of xenon TPCs in the search for 0𝝂ββ decay in Xe-136. The main goal is to achieve a position resolution of the order of ~100 µm at the decay Q-value (~2.5 MeV) by using a densely packed array of silicon photomultipliers (SiPMs), doping the xenon with H2 and D2 and optimising the geometry of the electrode grids. This opens the possibility of reconstructing electron track topologies and exploring the unique signature of this decay compared with the main backgrounds. The ambition is to take the Xe-136 0𝜈𝛽𝛽 half-life sensitivity of a G3 detector over the 10^28 yr level even using natural xenon, completely excluding the inverted hierarchy scenario and significantly increasing the possibility of observing this decay.