Development of SiPM-based spectrometers for the UCNtau and UCNA+ experiments

East Tennessee State University, Johnson City TN

Investigators

Abstract

The free neutron radioactively decays into a proton, electron, and anti-neutrino. The rate at which this process occurs, and the direction of the ejected particles, is determined by parameters of the weak nuclear force. Precision studies of these parameters provide a window into the fundamental physics governing our universe and can identify new physics. The goal of future experiments is to be sufficiently sensitive to detect new physics that is not currently part of the Standard Model of Forces and Particles. To increase the sensitivity of these experiments new modern technologies and techniques must be integrated into the experimental methods. This award will support the investigation of Silicon Photomultiplier based neutron and electron detectors that will mitigate systematic uncertainties in previous iterations of neutron decay experiments. The project will provide undergraduate researchers with essential hands-on training in skills that will prepare them for the national STEM workforce. In collaboration with the ultracold neutron physics group at Los Alamos National Laboratory this research will enable higher precision measurements of the neutron lifetime, the beta-asymmetry parameter ‘A’, and a new search for the neutron’s electric dipole moment. Three experimental goals are outlined in this project. First, provide a silicon photomultiplier-based scintillation detector for a <0.2% measurements of ‘A’ for the UCNA+ experiment. The detector will eliminate the multi-wire proportional counter used in UCNA that was the source of backscattering and energy loss systematics. This technology will enable a similar detector scheme for high rate counting in the UCNtau experiment. Second, provide neutron time of flight spectrometers for online assess of the ultracold neutron velocity spectrum which is essential for understanding systematic effects in all the experiments hosted by LANL. Finally, provide a design of a lightly enriched uranium insert for the LANL ultracold neutron source capable increasing the production by a factor of four. 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.