CAREER: Pivoting XENONnT to Neutrinos and Anomaly Resolution

To identify dark matter, understand the nature of the neutrino, or discover why the Universe is made of matter instead of a mixture of matter and antimatter would all constitute major advances. This award will follow-up on previous measurements by the XENON1T collaboration that may provide evidence of physics beyond the Standard Model, such as the neutrino magnetic moment or solar axions.

The observed electronic recoil (ER) excess is the first result of this type produced by the liquid-xenon community. The award will improve the energy resolution and its robustness by leveraging the group's reconstruction work to capture the microphysical details and by exploiting their machine-learning R&D activities. The award will provide a range of broader-impact activities that focus on the societal benefits of data literacy, where the activities proposed are a continuation of the group’s Physics and Computation Summer program.

The long-term goal of this project is to increase the number of students in the STEM pipeline and, more specifically, to increase the number of students who become data-intensive scientists and engineers. This work would provide data-science training for physicists through a project-based interdisciplinary course. Such training is indispensable to partaking in computationally oriented research.

While working on a diverse set of advanced-analysis (machine learning) projects, the PI developed a unique set of skills to determine whether this excess is a major discovery or a subtle experimental effect. The investigators will employ two work packages: 1) to revisit the core aspects of the analysis of the ER spectrum and apply the results to data from XENONnT (the XENON1T upgrade).

They will understand ER-modeling uncertainties by using the more complete Noble Element Simulation Technique (NEST) ER model, which the PI’s group maintains, to fit data simultaneously from other experiments by using likelihood-free inference techniques; and 2) to generalize the techniques to higher energies to measure neutrinoless double beta decay, while performing phenomenological studies of next-generation detectors. Motivated by the excess ER interactions, the PI will test the Majorana hypothesis by studying this beta decay process, which is observable only if neutrinos are Majorana particles.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.