This project is focused on the testing of basic symmetries, and determination of fundamental constants, of the standard model. The proposed research involves the muLan/muCap experiments at the Paul Scherrer Institute, Switzerland, and expt. 869 at the TRIUMF facility, Canada. The experiments will determine the Fermi constant of the electroweak interaction to part-per-million accuracy, the induced pseudoscalar coupling constant of the proton's weak interaction to six percent accuracy, and test isospin symmetry in pion-nucleon interactions to high precision. Both the muLan experiment and the muCap experiment at PSI involve high precision measurements of positive/negative muon lifetimes and utilize new technologies including an intense pulsed muon beam, novel detectors, and high-speed electronics and data acquisition. Expt. 869 utilizes a reconfigured RMC spectrometer as a pi0 spectrometer for the investigation of the elementary interaction between pions and nucleons. Both muCap and expt 869 will address the realization of two important symmetries of quantum chromodynamics -- chiral symmetry and isospin symmetry -- in low energy interactions of protons and neutrons. The determination of the Fermi constant by the muLan experiment will both determine a fundamental parameter for all electroweak calculations and facilitate the precision testing of the standard model.
The project includes several areas for broader impact. The PI will continue his involvement of physics majors, computer science graduate students and physics graduate students in both the experimental program and the related development of high-speed electronics and data acquisition. The PI will also continue his efforts in the teaching of symmetry principles and conservation laws in classes for physics and engineering majors. Moreover, the measurements themselves are of textbook quantities (e.g. the Fermi constant and the muon magnetic moment) and have broad impact in their own right.
