Standard Model Tests via Rare Pion Decay Measurements

This award supports new research for the PI and graduate students on the development of an innovative Rare Pion Decay Spectrometer at the Paul Scherrer Institute, Switzerland. The proposed measurements will provide both important tests of the Standard Model (SM) of particle physics and importance searches for unknown particles and interactions of nature. Such measurements will have a broad impact and lasting legacy in nuclear physics, particle physics, and astrophysics. The PI and graduate students are responsible for the development of the high-performance data acquisition and real-time processing system for the spectrometer. This work includes the engineering for PCIe-over-fiber readout of FPGA devices and real-time pulse fitting for lossless compression. The PI's group will also contribute to physics simulations and physics analysis through development of rule-based and machine learning algorithms for particle tracking and vertex finding. The project provides broader impact through involvement and training of high school students, physics majors and graduate students. The group's involvement in large-scale data acquisition, analysis and simulation also expose students to new technologies and paradigms in computing. The project goals include a 15-fold improved measurement of the ratio of the pion's electronic-to-muonic decays, a 6-fold improved measurement of the pion's beta decay, as well as order-of-magnitude improved searches for exotic particles including dark matter, light axions, and heavy neutrinos. The ratio of pion electronic-to-muonic decays offers the most stringent test of lepton universality and the pion beta decay addresses tensions in the CKM matrix. The development of the silicon-strip target, low-mass tracker, and LYSO calorimeter components of the spectrometer will significantly advance experimental instrumentation for nuclear physics. 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.