Reprint Server

Beam Dynamics Corrections to the Run-1 Measurement of the Muon Anomalous Magnetic Moment at Fermilab

Abstract

This paper presents the beam dynamics systematic corrections and their uncertainties for the Run-1 dataset of the Fermilab Muon g − 2 Experiment. Two corrections to the measured muon precession frequency ω_a^m are associated with well-known effects owing to the use of electrostatic quadrupole (ESQ) vertical focusing in the storage ring. An average vertically oriented motional magnetic field is felt by relativistic muons passing transversely through the radial electric field components created by the ESQ system. The correction depends on the stored momentum distribution and the tunes of the ring, which has relatively weak vertical focusing. Vertical betatron motions imply that the muons do not orbit the ring in a plane exactly orthogonal to the vertical magnetic field direction. A correction is necessary to account for an average pitch angle associated with their trajectories. A third small correction is necessary, because muons that escape the ring during the storage time are slightly biased in initial spin phase compared to the parent distribution. Finally, because two high-voltage resistors in the ESQ network had longer than designed RC time constants, the vertical and horizontal centroids and envelopes of the stored muon beam drifted slightly, but coherently, during each storage ring fill. This led to the discovery of an important phase-acceptance relationship that requires a correction. The sum of the corrections to ω_a^m is 0.50 ± 0.09 ppm; the uncertainty is small compared to the 0.43 ppm statistical precision of ω_a^m.

Muon g-2 Collaboration, Physical Review Accelerators and Beams, 24 (2021) 044002. DOI: 10.1103/PhysRevAccelBeams.24.044002

Download

Click on the icon to download the corresponding file.

Download Adobe PDF version (3093024 Bytes).

Go Back to the reprint server.
Go Back to the home page.

This page is maintained by Kyoko Makino. Please contact her if there are any problems with it.