NSF Award
2013205
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 Elastic Neutrino-Nucleus Scattering (CEvNS) is a mechanism of neutrino interaction predicted more than four decades ago, but only recently observed by the COHERENT collaboration using a Cesium-Iodide detector. The probability of neutrino detection via CEvNS is much larger than for any other known mode of neutrino interaction with matter, but the signals generated are subtle, hard to isolate, and dependent on the elemental composition of the detector. Measuring these interactions helps to constrain the many unknown properties of the evasive neutrino and contributes to the refinement of the underlying theories of particle interactions. <br/> <br/>This proposal supports the North Carolina Central University (NCCU) neutrino group to continue its participation in the COHERENT Collaboration activities including the deployment of a multi-ton Sodium Iodide detector and the development and deployment of a Germanium detector array. The full range of detectors (Cesium Iodide, Sodium Iodide, and Germanium) will allow for a robust test of the theory describing the CEvNS interaction. NCCU is a master’s granting, primarily undergraduate Historically Black College or University (HBCU) in which the majority of students participating are African-American or Hispanic-American. This award will support the engagement of NCCU students in forefront physics research. The award also supports the NCCU Telescope Team in which students from the neutrino group contribute to local Outdoor Astronomy programs, and give lectures to high-school STEM programs and the public on the use of nuclear physics techniques for analysis of cultural artifacts. In addition, the PI will initiate activities with the Clement Early College High School students at NCCU to participate in the building and deploying of environmental monitoring instruments including radiation detectors.<br/> <br/>The CEvNS interaction is one of the largest cross sections relevant to supernova dynamics and plays an important role in core collapse processes because the CEvNS cross-section is predicted, in the Standard Model, to scale approximately with the square of the target nucleus neutron number, N. This N-squared dependence is in fact the signature of the coherent nature of the interaction, indicating that the target nucleus recoils as a whole rather than as an individual neutron or proton. In order to fully probe the CEvNS interaction, a range of nuclei must be tested. This proposal enables NCCU to contribute to the deployment of a multi-ton NaI detector array and to develop a shielded array of low-background, low-threshold, p-type point contact Ge detectors. In addition to the spectral N-squared dependence, the precision CEvNS measurements in Ge will lead to information on nuclear form factors. CEvNS measurement in the odd-proton nucleus 23-Sodium will hopefully be sensitive to axial vector contributions to the interaction. <br/> <br/>The measurements of neutrino scattering cross sections are of interest to a broad range of physics communities. With a well-predicted Standard Model cross section, deviations from the expected values become a probe of non-standard neutrino interactions and may put limits on light mediator particles. The CEvNS interaction with solar and atmospheric neutrinos, for example, is an irreducible background to direct dark matter weakly interacting massive particles (WIMP) searches.<br/><br/>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.
