Prospect of the NUCLEUS Experiment at Chooz for Coherent Elastic Neutrino-Nucleus Scattering and New Physics Searches

TL;DR

The NUCLEUS experiment at Chooz aims to detect coherent elastic neutrino-nucleus scattering at very low energies, providing new insights into neutrino properties and potential physics beyond the Standard Model.

Contribution

This work presents sensitivity projections and a likelihood framework for the NUCLEUS experiment, including handling of the low-energy excess and systematic uncertainties, to explore new physics scenarios.

Findings

Projected 4.7 sigma detection of CEvNS in one year

Potential to measure the weak mixing angle at unprecedented low momentum transfer

Constraints on neutrino charge radius and new mediators from CEvNS data

Abstract

The NUCLEUS experiment aims to measure coherent elastic neutrino-nucleus scattering (CE$\nu$NS) at unprecedentedly low nuclear recoil energies using gram-scale cryogenic calorimeters operated at the Chooz nuclear power plant in France. Access to recoil energies at the $\mathcal{O}(10~\mathrm{eV})$ scale enables CE$\nu$NS studies at extremely low momentum transfer and provides enhanced sensitivity to new physics. In this work, we present sensitivity projections for the upcoming NUCLEUS technical and physics runs, incorporating a data-driven treatment of the low-energy excess (LEE) observed during commissioning. We develop a likelihood framework that exploits reactor-power variation to disentangle signal and background in a low signal-to-background regime and to assess the impact of the dominant systematic uncertainties. For the Technical Run with a 7 g CaWO$_4$ target, we find competitive sensitivity to several scenarios beyond the Standard Model, which do not require a CE$\nu$NS observation. For the Physics Run, assuming complete suppression of the LEE, we project a 4.7 $\sigma$ observation of CE$\nu$NS with a statistical precision of about 20 % in 1 year, enabling a determination of the weak mixing angle at the lowest momentum transfer probed to date with CE$\nu$NS and leading CE$\nu$NS-based constraints on the neutrino charge radius and new mediator models.