Exploring low-energy neutrino physics with the Coherent Neutrino Nucleus Interaction Experiment

Abstract

The Coherent Neutrino-Nucleus Interaction Experiment (CONNIE) uses low-noise fully depleted charge-coupled devices (CCDs) with the goal of measuring low-energy recoils from coherent elastic scattering (CEνNS) of reactor antineutrinos with silicon nuclei. This standard model process has not yet been observed at recoil energies below 20 keV. We report here the first results of the detector array deployed in 2016, with an active mass of 73.2 g (12 CCDs), which is operating at a distance of 30 m from the core of the Angra 2 nuclear reactor, with a thermal power of 3.8 GW. A search for neutrino events is performed by comparing data collected with reactor on (2.1 kg-day) and reactor off (1.6 kg-day). The results show no excess in the reactor-on data, reaching the world record sensitivity down to recoil energies of about 1 keV (0.1 keV electron-equivalent). A 95% confidence level limit for new physics is established at an event rate of 40 times the one expected from the standard model at this energy scale. The results presented here provide a new window to the low-energy neutrino physics, which allows one to explore for the first time the lowest energies accessible through the CEνNS with antineutrinos from nuclear reactors.

Search for light mediators in the low-energy data of the CONNIE reactor neutrino experiment

“…The results in the recent CONNIE run discussed in ref. [23] From the lowest-energy bin of this figure, we see that the 95% C.L. upper limit established by CONNIE is 41 times above the SM prediction using the quenching factor measurements in ref.…”

“…The CONNIE detector is sensitive to recoil energies down to 1 keV. A search for neutrino events is performed by comparing data with the reactor on (2.1 kg-day) and the reactor off (1.6 kg-day), the results show no excess in the reactor-on data [23]. A model independent 95% Confidence Level (C.L.)…”

“…In this work we use the results recently published by CONNIE [23] to restrict the parameter space of two simplified extensions of the SM that have also been explored with the data of the COHERENT experiment. This approach shows the potential of experiments searching for CEνNS with low-energy reactor neutrinos to probe new physics in a way that is complementary to spallation neutrino experiments.…”

“…This limit is presented in ref. [23] as a model independent limit for a counting experiment in the lowest energy bin for the data in CONNIE. Here, we study this limit in the context of light mediators, as discussed in section 2.…”

“…For this reason we perform the search for the two extensions of the SM described in section 2, using only the lowest-energy bin of the limits published by the CONNIE Collaboration in ref. [23]. We leave for future work an analysis using the full spectral shape of the reactor data from CONNIE.…”