Russian physicists have shown that the elastic coherent scattering of reactor antineutrinos on xenon nuclei cannot exceed the Standard Model prediction by more than 60–90 times. To do this, they used the RED-100, a two-phase emission detector filled with liquid xenon, located near the nuclear reactor of the Kalinin Nuclear Power Plant. A paper describing the study is available on the preprint portal arXiv.org.
Elastic coherent scattering of neutrinos and antineutrinos by atomic nuclei is the most probable interaction of these particles with matter at energies up to several tens of megaelectronvolts. The cross section for this interaction is tens and even hundreds of times larger than the cross section for inverse beta decay. Therefore, scientists place great hope in this process, believing it will enable the monitoring of nuclear reactors and nuclear non-proliferation using compact neutrino detectors. However, the detector response to this scattering is extremely small, and thanks to technological advances, it was only detected in an accelerator experiment in 2017, despite being predicted nearly 50 years ago.
We recently reported that two liquid xenon detectors were able to detect (once, twice) this process from solar neutrinos, but both have a large mass of detector material, on the order of several tons, and are located in low-background underground laboratories. Detecting the coherent scattering of reactor antineutrinos is a much more difficult task due to the higher external radiation background. For example, CONUS—one of the most advanced reactor experiments in this field—has yet to detect this process.
A team of physicists led by Alexander Bolozdynya from the Moscow Engineering Physics Institute (MPI) obtained the first limitation of this process on xenon nuclei for reactor antineutrinos. To do this, the scientists used a two-phase emission detector filled with liquid xenon with a mass of approximately 130 kilograms in the active volume. The detector was located 19 meters from the nuclear reactor of the Kalinin Nuclear Power Plant and was surrounded by passive shielding from external background radiation, consisting of layers of copper and water.
To detect the excess detector count rate caused by antineutrino signals, physicists compared data collected during reactor offline and reactor online periods. During the data analysis, the scientists were able to suppress the external background by several orders of magnitude. However, this was not enough to detect differences in detector count rates depending on reactor operation. However, it did allow the physicists to establish the first constraint on the elastic coherent scattering of reactor antineutrinos on xenon nuclei, which turned out to be 60-90 times larger than the Standard Model prediction.
Scientists note that it is possible to detect the elastic scattering of reactor antineutrinos using the RED-100 detector if xenon is replaced with argon, which is expected to have a lower level of specific background radiation. To test this hypothesis, physicists are already conducting technical tests at MEPhI.
Scientists are studying neutrino interactions across various energy ranges. For example, we recently reported that physicists have likely detected a neutrino with a record-breaking energy of tens of petaelectronvolts.
