German physicists were able to detect a signal from elastic coherent scattering of reactor antineutrinos on atomic nuclei using the germanium detector CONUS+. The statistical significance of the detection was 3.7 standard deviations. The results of the work are available on the preprint site arXiv.org.
Seeing the process of elastic coherent scattering of reactor antineutrinos is a difficult task due to the extremely low recoil energies of the nuclei of the recording substance. We recently wrote that this has not yet been done using a liquid xenon detector. However, scientists have already learned to register this process for accelerator neutrinos, and last year they saw it for solar neutrinos. The CONUS experiment came closest to registering this process for reactor antineutrinos, but did not have time to collect enough data before the Brokdorf Nuclear Power Plant was completely shut down.
A group of scientists from the CONUS collaboration led by M. Lindner from the Max Planck Institute for Nuclear Physics succeeded in detecting elastic coherent scattering of reactor antineutrinos on germanium (Ge) nuclei. To do this, they transported the CONUS detector to the Leibstadt nuclear power plant in Switzerland and modified it to lower the energy threshold for detecting events. CONUS+ was located 21 meters from the nuclear reactor, which provided a flux of 1.5 × 1013 antineutrinos per square centimeter per second. The scientists collected data over 119 days of reactor operation.
As a result of the data analysis, the physicists found 395 ± 106 events that prevailed over the background. This is consistent, according to the authors, with the prediction of the Standard Model, according to which 347 ± 34 events were expected. The statistical significance of the detection was 3.7 standard deviations.
For more information about elastic coherent scattering of neutrinos on atomic nuclei, read our interview with Dmitry Akimov, a participant in the first experiment in which this process was recorded.