Search for coherent elastic neutrino-nucleus scattering at a nuclear reactor with CONNIE 2019 data

TL;DR

The CONNIE experiment analyzed 2019 data to search for coherent elastic neutrino-nucleus scattering at a nuclear reactor, setting upper limits on interaction rates that are still above standard model predictions.

Contribution

First analysis of CONNIE 2019 data with improved detection threshold, providing new upper limits on neutrino interactions at low energies.

Findings

No excess detected at low energies in reactor-on vs. off spectra.

Set upper limits on neutrino interaction rates at 95% confidence level.

Limits are 66-75 times the standard model prediction.

Abstract

The Coherent Neutrino-Nucleus Interaction Experiment (CONNIE) is taking data at the Angra 2 nuclear reactor with the aim of detecting the coherent elastic scattering of reactor antineutrinos with silicon nuclei using charge-coupled devices (CCDs). In 2019 the experiment operated with a hardware binning applied to the readout stage, leading to lower levels of readout noise and improving the detection threshold down to 50 eV. The results of the analysis of 2019 data are reported here, corresponding to the detector array of 8 CCDs with a fiducial mass of 36.2 g and a total exposure of 2.2 kg-days. The difference between the reactor-on and reactor-off spectra shows no excess at low energies and yields upper limits at 95% confidence level for the neutrino interaction rates. In the lowest-energy range, 50-180 eV, the expected limit stands at 34 (39) times the standard model prediction, while the observed limit is 66 (75) times the standard model prediction with Sarkis (Chavarria) quenching factors.