Transient Field Effects for Muon g-2 at Fermilab

Speaker: Nicholas Kinnaird

When: October 28, 2015 (Wed), 11:00AM to 12:00PM (add to my calendar)
Location: PRB 261

This event is part of the Preliminary Oral Exam.

Examining Committee: Lee Roberts, Shyam Erramilli, James Miller, So-Young Pi


Elementary particles have intrinsic magnetic moments related to their spins. In the Standard Model the lepton magnetic moments scale as the Landé g-factor, which differs slightly from 2 due to virtual loops containing photons and the known massive particles. The contributions from such heavy particles scales as the lepton mass squared. Thus the sensitivity to heavy particles both inside and outside the Standard Model will scale as (mμ/me)2 ≈ 43000 for the muon compared to the electron. By measuring the magnetic moment of the muon to high precision, the completeness of the Standard Model can be tested, and speculative extensions constrained. The Muon g-2 experiment at Fermilab is the latest g-2 experiment which has the goal of measuring the magnetic moment of the muon to 140 ppb.

From such a high degree of measurement precision we then require a precision of 70 ppb on the experimental magnetic field used to measure the spin precession frequency. I have studied the effects of external transient fields on this precision field, including the effects of the ambient 60 Hz and nearby booster accelerator. By measuring their magnitudes at locations in the experimental hall and performing magnetic field analysis using the finite elements software Opera, I have shown that these effects lie below their allowed error budget of 5 ppb, and can be ignored beyond adding a small systematic error to the final measurement. Going forward, other transients will by analyzed in the same way.