J. Wendel | Search arXiv

arXiv2026

High significance measurement of reactor coherent elastic neutrino-nucleus scattering on germanium by CONUS+

We report the most precise measurement to date of coherent elastic neutrino-nucleus scattering (CE$ν$NS) from reactor antineutrinos using the CONUS+ high-purity germanium detectors at the Leibstadt nuclear power plant. With an exposure of 1296 kg$\cdot$days reactor-on, a blind likelihood analysis yields $1555 \pm 152$ CE$ν$NS events, with a significance of 10.2 $σ$, in agreement with the Standard Model expectation of $1701 \pm 198$ events within 0.6 standard deviations. The result also determines the weak mixing angle at a momentum transfer of about 10 MeV, $\sin^2θ_W = 0.225 \pm 0.022$, consistent with the Standard Model prediction.

hep-ex↗

arXiv2026

Analysis of CONUS+ run 2: Detector performance, background model and CE$ν$NS measurement

Coherent elastic neutrino-nucleus scattering (CE$ν$NS) provides a uniquely sensitive probe of neutrino properties, but its detection requires pushing energy thresholds to the sub-keV scale while controlling backgrounds. The CONUS+ experiment, located at the Leibstadt nuclear power plant, reported the first observation of CE$ν$NS using reactor antineutrinos in 2025. Following a detector upgrade that replaced three of the original 1 kg high-purity germanium detectors with larger 2.42 kg diodes, this paper presents the analysis of the CONUS+ run 2 dataset, including the detector characterization, the background model, the signal prediction and expected sensitivity, and the extraction of the CE$ν$NS signal. The new detectors reach a background level per unit mass reduced by approximately a factor of two relative to the original detectors, while reaching energy thresholds between 140 and 170 eV$_{ee}$. With an exposure of 1296 kg$\cdot$days reactor-on and 86 kg$\cdot$days reactor-off, a blind likelihood analysis fitting directly the number of signal counts yields $N_s = 1555 \pm 152$ CE$ν$NS events, corresponding to a significance of 10.2$\,σ$. The result is in agreement with the Standard Model expectation of $1701 \pm 198$ events, with $N_s/N_{\mathrm{SM}} = 0.91 \pm 0.14$.

hep-ex↗