Directional recoil detection

Abstract

Dark matter remains one of the most profound mysteries in modern physics. Despite extensive astrophysical and cosmological evidence supporting its existence, its fundamental nature continues to elude us, driving the need for more sensitive experiments. Among these, direct detection experiments seeking to detect Weakly Interacting Massive Particles (WIMPs) through nuclear recoils have made significant progress, ruling out large regions of parameter space. As detectors increase sensitivity to probe lower masses and smaller cross sections, the once negligible neutrino background, known as the neutrino fog, becomes increasingly significant. For conventional detection methods, this background will eventually overshadow potential WIMP signals, limiting their ability to continue searching for WIMP dark matter. This dissertation focuses on directional recoil detection as a means to overcome the neutrino fog and extend dark matter searches into uncharted parameter space. This technique leverages the unique directional signature of galactic dark matter, which enables distinguishing the signal from backgrounds and unambiguously confirming the galactic origin of a positive signal. In this dissertation are four papers addressing different aspects of future directional recoil detection experiments and an exposition of the next generation detector in the Vahsen lab, the CYGNUS HD40. This dissertation presents several key contributions across the four papers and the detector exposition. A new gas mixture is proposed to enhance particle identification, along with a set of observables that can improve identification performance by up to two orders of magnitude. A novel deep learning method is developed for probabilistically predicting 3D direction, and an application of the method to electron recoil simulations demonstrates that it is capable of significantly enhancing directional performance while estimating directional uncertainty accurately. A detailed experimental comparison of various x/y strip readout configurations is conducted, providing insights for the design of future detectors and uncovering previously overlooked effects. A new method is developed for predicting the angular resolution of electrons in gas. The method is easy to compute if the electron energy and basic detector properties are known, making it a valuable tool for predicting detector performance and optimizing detector design. Finally, this dissertation introduces the CYGNUS HD40 detector, a step that could pave the way for scalable directional detectors in the future.