Low-Threshold Modular Detectors for Coherent Elastic Neutrino-Nucleus Scattering

Northwestern University, Evanston IL

Investigators

Abstract

The goal of this R&D award is to develop Transition-Edge Sensor (TES) detectors optimized for measurements of Coherent Elastic Neutrino-Nucleus Scattering (CEvNS) with low-energy thresholds two orders of magnitude lower than the CsI detectors used for the initial CEvNS measurement. These detectors will open a new window at low-recoil energies to study this relatively new channel in neutrino physics that has yet to be fully explored. By measuring the neutrino spectrum from a reactor, and comparing it to the standard model predictions, we gain sensitivity to physics beyond the Standard Model in scenarios including 1) an anomalous neutrino magnetic moment, 2) Non-Standard Interactions (NSI) of neutrinos, and 3) neutrinos coupling to new particles beyond the Standard Model. At the same time, they will enable a study of the low energy end of the reactor antineutrino flux that is inaccessible to inverse-beta-decay detectors and a search for possible sterile neutrinos, which have been postulated to exist but have never been seen. In pursuit of this goal, there are four objectives: (1) perform a detailed study to model and optimize a low-threshold TES-based CEvNS experiment focusing on detector performance, backgrounds, and science reach, (2) fabricate several prototype detectors based on the outcome of (1), (3) test these detectors and compare their performance to the models, and (4) train a new generation of neutrino experimental physicists. The work has a broad impact that extends beyond neutrino physics. TES detectors have applications in cosmology, astronomy, industry, and defense. This activity will contribute to the training of undergraduate and graduate students and postdoctoral researchers, continuing the group’s commitment to mentoring undergraduates from underrepresented groups by participating in the Summer Research Opportunities Program (SROP) at Northwestern. The group will evaluate TES designs for optimizing the science output of a CEvNS experiment at a nuclear reactor. Given a neutrino flux at the detector, they will consider the TES device physics, target materials and mass per detector, readout multiplexing architectures and achievable mass with these parameters, detector packaging and installation in a cryogenic system, backgrounds, shielding, and calibration. They will fabricate several TES sensors on standard silicon wafers based on the outcomes of the optimization study. The Northwestern EXperimental Underground Site (NEXUS) at Fermilab will be used to test these prototype detectors and compare their performance to their models. Calibrations will be performed with optical and X-ray sources and a dedicated neutron beam and backing detector array to accurately report the response to low-energy nuclear recoils. 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.