Precision Measurements and Fundamental Symmetries

Regents Of The University Of Michigan - Ann Arbor, Ann Arbor MI

Investigators

Abstract

Precise experimental tests of fundamental particle properties are now a well-established way to search for new laws of nature beyond our current physical knowledge. The research presented in this proposal challenges precise Standard Model predictions and could provide solid signals of new physics by measuring the magnetic-moment anomaly of the muon, a known elementary particle that is produced in abundance at the Fermi National Accelerator Laboratory. The proposed research is also to study the detailed behavior of the radioactive decay of neutrons. This work addresses questions at the deepest level: what is matter made of, how did it come to be and how does it interact? At the same time, this research addresses the technical demands of the experiments by pushing the limits of magnetic field measurement to a higher level. The existing 3.6-sigma difference between the Standard-Model prediction and the experimental value of g-2 of the muon provides a persistent laboratory signal of new physics, and we have the opportunity to advance the precision and strengthen the signal to reach discovery level. As part of the Fermilab Muon g-2 collaboration, our goal is to improve the experimental precision by a factor of four, which would result in a 7-sigma signal if the central value does not change, or even larger if the theory error is reduced. The University of Michigan group has shifted its effort from fundamental neutron physics with expertise in neutron polarization and precision neutron polarimetry to the problem of measurement of the muon-storage ring magnetic field. This expertise and experience in precision spin-precession and NMR-based magnetometry with polarized 3He will be applied to the problem of absolute calibration of the magnetic field measurement system and determining the systematic errors on the field measurement. In particular, this research will fund: 1) development of NMR techniques and systematics of the NMR-based magnetic-field measurement system and 2) work towards an absolute measurement of the 3He magnetic moment in a Penning trap. Furthermore, the proposed research will complete the development of the SNS beam for the Nab experiment, specifically the determination of the residual polarization of the Fundamental Neutron Physics Beamline (FNPB) beam using a 3He spin filter.