Coherent Elastic Neutrino-Nucleus Scattering (CEvNS) – From Observation to Impact

In 1974, Freedman conjectured that given the evidence of neutrino induced neutral-current interactions, then coherent elastic neutrino nucleus scattering (CEvNS) would exist, be enhanced, and provide a probe into nuclear form factors of the weak neutral current. He states that this "suggestion may be an act of hubris, because the inevitable constraints of interaction rate, resolution, and background pose grave experimental difficulties" [1]. Indeed, after early experimental attempts, people turned to the 'easier' task of measuring dark matter. With advances in techniques to measure the very low-energy signal from the recoiling nucleus, and the availability of intense neutrino sources, the COHERENT collaboration observed the CEvNS interaction for the first time in 2017 using a CsI target-detector at a stopped pion neutrino source [2]. Multiple international collaborations are tackling the experimental challenge to measure CEvNS in various target materials located at accelerator or reactor neutrino sources. With proven methods, CEvNS has evolved into a probe and is being developed for the detection of supernova neutrinos. The current results put constraints on non-standard neutrino interactions since deviations in rate or shape of the well-predicted cross section could indicate new contributions to the interaction rate. CEvNS is a background limit to low-mass, direct dark matter searches, while the CsI measurement constrained the existence of accelerator produced, sub-GeV scalar dark-matter candidates [3]. Future precision measurements will reach the goal of probing nuclear form factors, in addition to being sensitive to the neutrino magnetic moment that is another indication of beyond-the-standard-model physics. The exciting possibilities of CEvNS measurements will be presented.