The Pitch and Electric Field Corrections to the Anomalous Muon Spin Precession Frequency for the Muon g - 2 Experiment

The Muon g - 2 Experiment at Fermilab recently reported a new measurement of the muon's anomalous magnetic moment, a_μ = (g_μ - 2)/2, with a relative uncertainty of 460 parts-per-billion (ppb). The experiment uses a highly uniform magnetic storage ring to contain a polarized muon bunch, whose daughter particles are detected by calorimeters. This signal encodes the anomalous precession of the muon spin relative to the momentum at a frequency ω_a, which is directly proportional to a_μ. However, beam dynamics effects perturb the relationship by hundreds of ppb, necessitating corrections to the measured ω_a. One effect, called the pitch correction, is associated with oscillations induced by vertically focusing electric quadrupoles. Another, called the electric field correction, originates from the radial component of the quadrupoles' electric field. Both corrections must increase the observed ω_a in order to restore the proportionality with a_μ. In this talk, we present the analysis of the pitch and electric field corrections during the experiment's Run 1 measurement period.