Using low-energy neutrino scattering to test the standard model with the COHERENT experiment

Abstract: Neutrinos are the most common massive particles throughout the universe, yet many of their fundamental properties remain elusive. Of the standard model (SM) forces, they only interact with the weak force – meaning they rarely interact with matter. This makes precision neutrino measurements promising avenues for discovering new physics beyond the SM that couples feebly to SM particles. A new field has emerged focusing on measuring coherent elastic neutrino-nucleus scattering (CEvNS) since its first detection in 2017 by the COHERENT collaboration. CEvNS is a low-energy neutrino process where a neutrino scatters off a nucleus, transferring a detectable, though small, kinetic energy to the recoiling nucleus. The CEvNS scattering rate is precisely predicted by the SM but can be dramatically altered by beyond-SM scenarios making the process ideal for illuminating new physics.

We will discuss an overview of CEvNS and the COHERENT experimental program. Our most recent measurement, using a 14.6-kg CsI[Na] scintillation detector deployed at the Spallation Neutron Source (SNS), bridged the gap between first-light and precision measurements. This small detector has placed leading constraints on sub-GeV accelerator-produced dark matter and neutrino-quark beyond-SM interactions. We will also discuss ongoing efforts to survey the CEvNS cross section on multiple nuclei, with Na, Ar, and Ge targets currently deployed. This precision program utilizing multiple targets will also be sensitive to dark photons, sterile neutrino oscillations, and deviations in the weak mixing angle which are all theoretically motivated areas for new physics to appear. We highlight the future sensitivity of the broad COHERENT program to discovery of these beyond-SM particles.