Inverse beta decay and coherent elastic neutrino nucleus scattering – a comparison

Many neutrino experiments involving low-energy neutrinos rely on inverse beta decay (IBD), including those studying neutrino oscillations at nuclear reactors, and for applications in reactor monitoring and the detection of neutrinos emitted from spent nuclear fuel. IBD reactions can occur only for electron antineutrinos with energy above a threshold of 1.806 MeV. Below this threshold, the signature of neutrinos is accessible via coherent elastic neutrino-nucleus scattering (CEνNS), a threshold-less reaction. CEνNS was observed for the first time in 2017 at 6.7σ confidence level after forty years of experimentation, albeit with neutrinos of about 10 times larger energy than those from reactors. Here we assume also that neutrinos from reactors and other MeV-sources eventually will be detected using CEνNS. In this paper, we use neutrino fluxes measured from reactors and their cross sections to compute the energy spectra of U, U, Pu, and Pu, and determine and compare neutrino detection event counts using either IBD or CEνNS. This characterization will inform future detector choices and is directly applicable to various neutrino sources, including reactor neutrinos, spent fuel neutrinos, and geoneutrinos. The result is potentially useful in monitoring spent nuclear fuel and reactors, in support of nuclear nonproliferation safeguards objectives.