Beam Dynamics Challenges in the Muon g-2 Experiment

The muon's anomalous magnetic moment a_μ has hinted at physics beyond the standard model for nearly 20 years. The Muon $g-2$ experiment at Fermilab aims to measure a_μ to 140 parts per billion (ppb) precision. The 460 ppb result from its first data run (Run-1), released in 2021, agreed with the previous 2006 Brookhaven Muon $g-2$ result. The experimental average stands in tension with the standard model theory a_μ prediction by 4.2 σ. The result of Run-2/3 data analysis is set be released in summer 2023, and will improve on the Run-1 precision by a factor of two. With the data collected in all six runs, the experiment is on track to produce a 140 ppb measurement of a_μ. If the experiment and theory central values are both unchanged, the tension would exceed 5 σ. The measurement is accomplished by injecting muons into a magnetic storage ring and precisely measuring two observable frequencies: ω_a, the muons' anomalous precession frequency, and \tilde{ω}'_p, the precession frequency of protons which determines the magnetic field strength experienced by the muons. This thesis presents a selection of muon beam dynamics effects which are critical for reaching the experiment precision goal. A system of detectors assists with the challenging beam injection into the storage ring, and a measurement of the injected beam provides input for simulating the stored beam dynamics. A new method is introduced to reduce a critical systemic caused by time dependence in the stored beam momentum, enabled by a detector which directly profiles the stored beam. Finally the analysis of \tilde{ω}'_p, the muon-weighted magnetic field, for the Run-2/3 result is presented. Systematics of \tilde{ω}'_p due to beam effects are evaluated in detail, and shown to be sub-dominant.

Author dc:creator

• MacCoy, Brynn

Advisor dc:contributor.advisor

• Kammel, Peter

• anomalous magnetic moment
• beam dynamics
• particle physics
• precision muon physics

Statement dc:rights

• CC BY

Language dc:language.iso

en_US

Handle dc:identifier.uri

http://hdl.handle.net/1773/50899

OAI identifier oai:identifier

oai:digital.lib.washington.edu:1773/50899