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Digital archive of theses discussed at the University of Pisa

 

Thesis etd-03122024-201534


Thesis type
Tesi di dottorato di ricerca
Author
COTROZZI, LORENZO
URN
etd-03122024-201534
Thesis title
Measurement of the muon anomalous precession frequency with the Run-2/3 data in the Muon g-2 experiment at Fermilab
Academic discipline
FIS/01
Course of study
FISICA
Supervisors
tutor Prof. Venanzoni, Graziano
relatore Prof. Batignani, Giovanni
Keywords
  • anomalous precession frequnecy
  • experiment
  • Fermilab
  • Muon g-2
Graduation session start date
15/03/2024
Availability
Full
Summary
The measurement of the muon magnetic anomaly a_μ=(g_μ−2)/2, where g_μ is the g-factor of the muon, is one of the most accurate tests of the Standard Model (SM) theory of elementary particles. Its theoretical value is dominated by the QED Schwinger term α/2π≈0.00116, but all sectors of the SM contribute to the interaction of muons with a magnetic field through virtual particles in quantum loops.
On the experimental side, the anomaly can be measured very precisely, with a well-established technique. When muons are injected into a magnetic field, both their spin and their momentum vectors precess, and the precession frequency of the spin with respect to the momentum, the so-called "anomalous precession frequency", can be obtained as ω_a≡ a_μe/mB. This means that a_μ can be extracted by accurately measuring ω_a and B.
In the Muon g−2 experiment at Fermilab (E989), a 3.1-GeV spin-polarized beam of positive muons is injected into a storage ring of 14m of diameter, in the presence of a 1.45T magnetic field. The experiment published a new result in 2023, based on the 2019 and 2020 data (namely Run-2/3), in very good agreement with the previous experimental results. From the combination, the new experimental world average is a_μ(Exp)=116592059(22)×10−11(0.19 ppm).
The original work of this Thesis is presented in Chapters from 5 to 8: in particular, the "Ratio-Asymmetry" method, which was new with respect to Run-1, to analyze the anomalous ω_a frequency with Run-2/3 data. This method greatly reduces the sensitivity of ω_a to all slowly varying systematic effects, and it also achieves the maximum statistical power on ω_a by applying appropriate weights to the data. My results for ω_a were averaged with those from 5 other independent groups, to produce the final ω_a values and uncertainties that were published in 2023.
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