A COHERENT Next Step: Precision Measurement of CENNS Using PPC Germanium Detectors at the SNS

University Of Chicago, Chicago IL

Investigators

Abstract

Of all known elementary particles, neutrinos stand out for the difficulty involved in their detection, a result of their tiny probability of interaction with other forms of matter. Large (ton or multi-ton) detectors are typically involved. Coherent Neutrino-Nucleus Elastic Scattering (CEnNS) is a mechanism of neutrino interaction predicted more than four decades ago, and only recently measured by the COHERENT collaboration. The probability of neutrino detection via CEnNS is much larger than for any other known mode of neutrino interaction with matter, but the signals generated are subtle and hard to isolate. It is only through recent advances in radiation detection that it has become possible to access these signals. CEnNS opens up the possibility of employing small, handheld devices for neutrino detection, generating some interesting technological applications. This award will facilitate a next step in the investigation of this promising new type of neutrino interaction within COHERENT, funding the construction of state-of-the-art germanium detectors to be used at the Spallation Neutron Source at the Oak Ridge National Laboratory. The devices will measure CEnNS with an unprecedented precision, constraining the many still unknown properties of the evasive neutrino, and contributing to a refinement of the underlaying theories of particle interactions. Several aspects of the development of these devices will apply to their planned use in nuclear non-proliferation applications, where CEnNS can be exploited to monitor nuclear reactors against diversion of weapons-grade material. The planned measurement of the CEnNS energy spectrum will be performed in optimal conditions of signal-to-background ratio, large statistics, sensitivity to the full range of recoil energies, and detailed knowledge of detector response to nuclear recoils. The latter will be achieved through past, ongoing, and planned measurements of the germanium quenching factor for CEnNS-induced nuclear recoils, down to sub-keV energies. The modest uncertainties expected from this new CEnNS measurement will allow a very precise comparison to Standard Model (SM) predictions. A significant improvement of the present experimental sensitivity in a number of active areas of research in particle physics will result from this comparison: for instance, the study of electromagnetic properties of neutrinos, their non-standard couplings predicted by extensions of the Standard Model of particle physics, tests of dark matter models, and an improved sensitivity to a fourth sterile neutrino, to name a few. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.