• Nuclear, Particle, Astroparticle and Cosmology (NUPAC) Seminars

November 18, 2025 1:30 PM
PAIS 3205

Host:

Dinesh Loomba

Presenter:

Wesley Thompson (UNM)

The Migdal effect is a rare process where the sudden displacement of a recoiling nucleus induces the emission of an atomic electron. Several direct dark matter detection experiments have invoked this effect to extend their sensitivities to lighter masses. However, the Migdal effect has yet to be observed in nuclear scattering. The MIGDAL experiment is a neutron scattering experiment designed to unambiguously detect the Migdal effect. It does so through the utilization of a low pressure gas optical time projection chamber (O-TPC) detector in a high flux, monoenergetic (2.47 MeV) neutron beam at Rutherford Appleton Lab in the United Kingdom. The O-TPC is equipped with a Hamamatsu ORCA-Quest qCMOS camera, Indium Tin Oxide (ITO) strips, and a Hamamatsu R11410 photomultiplier tube (PMT), allowing for the full 3D reconstruction of the Migdal event topology.

In this talk, I will describe the detector subsystems and how they achieve 3D particle track reconstruction and directionality. Additionally, I will discuss my work characterizing two key aspects of the MIGDAL TPC: diffusion and energy resolution. Diffusion is among the chief factors limiting the detection of a faint Migdal electron at the vertex of an orders-of-magnitude brighter nuclear recoil. Thus, diffusion must be understood since this could heavily impact the expected detection efficiency of Migdal events. Considering that the MIGDAL experiment aims to not only observe the Migdal effect, but to characterize the Migdal theory, we require accurate energy reconstruction across three orders of magnitude in particle energies. This will involve accurately reconstructing the unique angular spectrum of nuclear recoils induced by the monoenergetic neutron beam. Exceptional angular resolution is therefore an essential aspect of this project, which is achieved through improved image processing and trajectory reconstruction. The methods I develop during these projects will provide an introduction into the topics that I will explore during the remainder of my PhD, such as low energy nuclear recoil directionality, electron recoil/nuclear recoil discrimination, and applying machine learning to the MIGDAL dataset.