Migdal effect: a way to light dark matter detection
IDPASC Portugal - PHD Programme 2019
2019 / 2020
Experimental Particle Physics | Astrophysics
Universidade de Coimbra
Laboratório de Instrumentação e Física Experimental de Partículas
For the past several decades, experimental efforts to directly detect dark matter (DM) interactions have focused mostly on Weakly Interacting Massive Particles (WIMPs) in the mass range above a few GeV. This limit was driven by the fact that most theoretical models predicted WIMP particles with a mass above ∼2 GeV, as well as technical difficulties in building a detector with sensitivity to lighter WIMPs. However, newer models of sub-GeV dark matter (including freeze-out DM, asymmetric DM and freeze-in DM) boosted interest in direct detection of such kind of less-massive WIMPs. Currently, the most sensitive WIMP detectors (LUX, PANDA-X, XENON-1T and future LZ and XENON-nT) are based on liquid xenon technology. For some time, it was assumed that liquid xenon DM detectors are not sensitive to this kind of light dark matter as low nuclear recoil energy combined with strong quenching would result in a signal below the detection threshold (~1 keV). However, as it was pointed out in recent theoretical studies, the energy of the nuclear recoil can be transferred to the atomic shell, resulting in emission of either a gamma-ray (bremsstrahlung) or an electron (Migdal effect). The energy deposited by either the gamma-ray or electron (~keV) will not be quenched thus enhancing the detectability of light dark matter. If confirmed experimentally, these effects will considerably extend the sensitivity range of the large liquid xenon detectors, currently under construction (LZ and XENON-nT) and would allow to probe lighter dark matter candidates otherwise inaccessible. We propose, in the framework of this project, to perform experimental verification of the Migdal effect in liquid xenon. In this project, the student will be integrated and supported directly by the LIP team, largely experienced in all aspects of liquid xenon detectors and direct dark matter detection (as members of ZEPLIN, LUX and LZ Collaborations). The work will comprise three main components: (1) Integration of the student in the LZ Collaboration team, including on-site work at Sanford Underground Research Facility (USA); (2) Feasibility study using the GEANT4 simulation toolkit of a setup for the direct measurement of the energy transfer mechanisms from nuclear recoils into bremsstrahlung and Migdal effect in liquid xenon; (3) Experiment planning and experimental validation using LZ detector neutron calibration facility.