Measurement of the muon anomalous precession frequency at the Muon g − 2 Experiment at Fermilab

Thesis/Dissertation · Sat Apr 01 00:00:00 EDT 2023

OSTI ID:2246737

Girotti, Paolo ^[1]

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1. Pisa U.

The anomalous magnetic moment of the muon, $$a_\mu = \frac{g-2}{2}$$ is the fractional deviation of the muon $$g$$-factor from the value of 2. It emerges as the cumulative effect of the virtual particles participating in the muon interaction with a magnetic field via quantum loop corrections. Its value encodes all the possible interactions between the virtual particles and, for this reason, represents an important test of the Standard Model (SM). In particular, any deviation from the SM theoretical evaluation could be due to new physics contributions. The new Muon $g-2$ (E989) Experiment at Fermilab is currently operating to repeat and improve the previous E821 experiment at Brookhaven National Laboratory (BNL), aiming to reduce the experimental error by a factor of 4 to the final accuracy of 140 parts per billion (ppb). On April 7th, 2021, the E989 collaboration published the first result based on the first year of data taking (Run-1), measuring $$a_\mu = 0.001~165~920~40(54)$$ with a precision of 460 ppb. The measured value is consistent with the BNL measurement and strengthens the long-standing tension with the data-driven SM prediction to a combined discrepancy of 4.2$$\sigma$$. On the theory side, however, new efforts involving lattice-QCD techniques are starting to question the current consensus on the theoretical prediction, demanding new improvements on both the experimental and theoretical sides. The E989 collaboration is now finalizing the analysis of Run-2 and Run-3 data and a new publication is expected in the first half of 2023 with a combined statistical uncertainty of 200 ppb. The anomalous magnetic moment $$a_\mu$$ is measured as the ratio between the muon spin anomalous precession frequency, $$\omega_a$$, and the average magnetic field experienced by the muons as they circulate in the storage ring. This thesis presents a precession frequency analysis of the Run-1 data and an evaluation of the related systematic uncertainties. A new positron reconstruction developed for the analysis of the subsequent data-taking periods, aiming to reduce some of the major systematic uncertainties of the $$\omega_a$$ measurement, is presented. The author's involvement in the production of the Run-2/5 data and in the precise calibration of the detectors is discussed. Finally, the complete Run-1 $$a_\mu$$ result is presented.

• Research Organization: Pisa U.
• Sponsoring Organization: US Department of Energy
• DOE Contract Number: AC02-07CH11359
• OSTI ID: 2246737
• Report Number(s): FERMILAB-THESIS-2023-12; oai:inspirehep.net:2738056
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS