Measurement of the muon spin precession frequency using the straw tracking detectors at the Fermilab Muon g-2 experiment

Thesis/Dissertation · Mon Jan 01 04:00:00 EST 2024

OSTI ID:2333016

Sweetmore, George Matthew ^[1]

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1. Manchester U.

The measurement of the anomalous magnetic dipole moment of the muon ($$a_{\mu}$$) has long stood as an excellent precision test of the Standard Model (SM). The Fermilab Muon g-2 experiment has recently finished data-taking and in July 2023 published its latest determination of $$a_\mu$$ with a world-leading precision of 0.2\,ppm. In this publication, it surpassed the systematic uncertainty goal defined in the TDR. The analyses of a dataset approximately four times larger than this recent publication is now underway. The principle measurement of the Muon g-2 experiment measures $$a_{\mu}$$ by taking the ratio of two frequencies; the anomalous precession frequency ($$\omega_a$$) and the muon-weighted magnetic field of the experiment's storage ring measured from the precession frequency of protons in water using nuclear magnetic resonance (NMR) probes. In all publications to date, $$\omega_a$$ has been determined using energy deposits in the 24 calorimeters. However, the Fermilab experiment has t wo straw tracker detectors measuring the time and momentum of charged particles which can in principle also be used to to measure $$\omega_a$$ and such a measurement can provide an invaluable cross-check of the calorimeter result with different, and reduced, systematic uncertainties. This thesis presents the first (blinded) determination of $$\omega_a$$ using just charged tracks from the straw tracking detectors as opposed to calorimeter energy deposits. This analysis was undertaken using the Run-2/3 dataset which represents approximately 25\% of the final dataset. A total uncertainty of 2.19\,ppm on $$\omega_a$$ was obtained which is dominated by the statistical uncertainty of 2.16\,ppm. Additionally two new methodologies important to the analysis of the straw tracking data have been developed: one to better determine the track arrival time ($$t_0$$) and one to determine the level of pileup in the tracking detectors. The new $$t_0$$ algorithm which incorporates angular information improves t he resolution on the determination of the $$t_0$$ by a factor of two and results in 19\% more tracks being successfully reconstructed. The data from the trackers is also used to determine the beam profile that weights the magnetic field in the determination of $$a_\mu$$ and in determining several of the systematic uncertainties in the calorimeter-based $$\omega_a$$ analysis. A detailed study of the impact of the internal alignment of the tracker, the $$t_0$$ and pileup on the determination of the beam position was undertaken and propagated through to an uncertainty in the $$\omega_a$$ determination. These uncertainties were used in the Fermilab Muon g-2 experiment's recent publication in Phys. Rev. Lett.

• Research Organization: Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
• DOE Contract Number: AC02-07CH11359
• OSTI ID: 2333016
• Report Number(s): FERMILAB-THESIS-2024-01; oai:inspirehep.net:2770306
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS