Nano-tracking detector for neutrinoless double beta decay characterization

Abstract

Of the many extensions to the standard model that could possibly generate neutrino mass, most necessitate the neutrino being a Majorana fermion. If this is the case, the rare process of neutrinoless double beta decay is predicted with half lives greater than about $10^{25}$ years. Many current and future experiments look for this decay by identifying a summed double beta energy at the Q value of the decay, but adding energy and angular measurements of the individual betas allows the underlying decay mechanism to be probed. A novel nano-tracking detector based on a clever combination of thin film CdTe devices will be presented here. This tracker will have order 100 nm spatial resolution in one dimension while measuring the energy deposition across the track length of electron recoils in the detector. This allows energy and angular correlation measurements of a potential neutrinoless double beta decay signal, as well as a unique background suppression capability. Deep learning algorithms will be used to reconstruct the electron paths, the double beta signals and perform the correlation analyses, and will simultaneously allow clear distinction between double betas and single beta or gamma-induced electronic recoils. The detector concept will be presented, along with preliminary studies, to demonstrate its operation and the physics reach for neutrinoless double beta decay. By exploiting recoil discrimination, an array of these detectors can potentially probe beyond the inverted hierarchy to either follow the next generation of neutrinoless double beta decay experiments or to serve as a post-discovery characterization experiment.