Methods for Data Analysis and Systematic Corrections in the Fermilab E989 Muon g-2 Experiment

A comparison of experimental measurements of the muon’s anomalous magnetic moment a with theoretical calculations thereof constitutes a test of the completeness of the Standard Model. At present, the most precise experimental result for a, from the completed Brookhaven experiment E821, stands some ~3.5 standard deviations from the Standard Model value, a quite intriguing result. This proposal describes contributions to the Fermilab muon g – 2 experiment E989. In this experiment, so-called “magic momentum” muons will be stored and subsequently undergo cyclotron orbits within a magnetic storage ring, with electric fields employed for confinement of those muons whose momenta differ slightly from the magic momentum condition. The difference between the muons’ cyclotron frequency and their spin precession frequency in the magnetic field is then, rather remarkably, directly proportional to the anomalous magnetic moment. This slight difference in the cyclotron and spin precession frequencies is then probed in the experiment via parity violation: as the muons decay, the direction of emission of the decay positrons (or electrons) is correlated with the direction of the muon’s spin. Thus, the time dependence of signals in detectors located along the ring (thus determining the muon’s momentum direction) is sensitive to the difference in these two frequencies. The work to be carried out in this proposal addresses two key aspects of the data analysis methods ultimately required for the extraction of a. First, systematic corrections to the cyclotron and spin precession frequencies are required on account of the muon transport through the (non-uniform) magnetic and electric fields. Here, the PI brings experience from involvement in neutron electric dipole moment experiments, where similar corrections for neutron transport through non-uniform magnetic and electric fields results in a systematic correction to the measured neutron spin precession frequency. Second, such a high-impact result calls for multiple analysis methods. Here, an alternative analysis method based on the integration of detector currents versus time (versus counting individual “detector hits” versus time) will be developed, in collaboration with the PI’s colleagues at the University of Kentucky.