Project Title: Measurement of Coherent Elastic Neutrino-Nucleus Scattering with Germanium Detectors at the SNS
M. P. Green, Principle Investigator, North Carolina State University
2701 Sullivan Drive, Admin III, Suite 240, Raleigh, NC 27695-7514
Coherent Elastic Neutrino-Nucleus Scattering (CEvNS) is a neutral-current process in which a neutrino interacts coherently with an entire nucleus. While the coherence of the process leads to a large cross section enhancement with increasing neutron number (∝ N2), the low momentum transfer results in difficult-to-detect low energy nuclear recoils. The COHERENT Collaboration has combined state-of-theart low-threshold detector technology with the intense flux of neutrinos generated at Oak Ridge National Laboratory’s Spallation Neutron Source (SNS) to detect CEvNS for the first time, and is developing it as a tool for searches for physics beyond the Standard Model, including Non-Standard Neutrino Interactions (NSIs), oscillations into sterile neutrinos, nuclear form factors, neutrino charge radii, and magnetic moments. The SNS combines neutrino energies that are ideally-suited for CEvNS detection with a time structure that enables powerful background reduction. The simultaneous deployment of multiple detectors with differing neutron numbers is critical for initial studies of this process.
P-Type Point-Contact (PPC) germanium detectors are well-matched to the problem of detecting CEvNS recoils; they combine low energy thresholds, excellent energy resolution, a well-understood quenching factor, and low intrinsic backgrounds. We are leading COHERENT’s efforts to deploy Gemini, a 16-kg array of PPC detectors at the SNS. The instrument assembly has been completed and initial commissioning data has been taken, with our first science run projected for the summer of 2023. We estimate a total of ~550 CEvNS events detected in the array per year, and a high-significance detection of the process within the first few months of array operation at the SNS.
With the support of this award we will make use of this unique instrument to measure the CEvNS cross section and recoil spectrum in germanium, and use these results to look for new physics beyond the standard model of particle physics. Specifically, the research program detailed in this proposal aims to:
- Commission and operate the Ge-mini detector array at the SNS.
- Perform the first measurement of the CEvNS recoil spectrum in germanium.
- Use the measured recoil spectrum in a combined analysis with the other COHERENT detector systems
to observe the N2 cross section dependence and constrain neutrino Non-Standard Interactions
(NSI).
- Assess the capabilities of Ge-mini and a potential future large-scale detector array to measure NSI,
electromagnetic properties of neutrinos, and other new physics.
We have the experience to accomplish these aims, make the first precision measurement of CEvNS in germanium, and in doing so add significantly to COHERENT’s capabilities.
