Magnetic-field measurement and analysis for the Muon g-2 Experiment at Fermilab


T. Albahri, University of Liverpool
A. Anastasi, Istituto Nazionale di Fisica Nucleare, Sezione di Pisa
K. Badgley, Fermi National Accelerator Laboratory
S. Baeßler, University of Virginia
I. Bailey, Lancaster University
V. A. Baranov, Joint Institute for Nuclear Research, Dubna
E. Barlas-Yucel, University of Illinois Urbana-Champaign
T. Barrett, Cornell University
F. Bedeschi, Istituto Nazionale di Fisica Nucleare, Sezione di Pisa
M. Berz, Michigan State University
M. Bhattacharya, University of Mississippi
H. P. Binney, University of Washington
P. Bloom, North Central College
J. Bono, Fermi National Accelerator Laboratory
E. Bottalico, Istituto Nazionale di Fisica Nucleare, Sezione di Pisa
T. Bowcock, University of Liverpool
G. Cantatore, Istituto Nazionale di Fisica Nucleare, Sezione di Trieste
R. M. Carey, Boston University
B. C.K. Casey, Fermi National Accelerator Laboratory
D. Cauz, Istituto Nazionale di Fisica Nucleare - INFN
R. Chakraborty, University of Kentucky
S. P. Chang, Institute for Basic Science, Daejeon
A. Chapelain, Cornell University
S. Charity, Fermi National Accelerator Laboratory
R. Chislett, University College London
J. Choi, Institute for Basic Science, Daejeon
Z. Chu, Shanghai Jiao Tong University
T. E. Chupp, University of Michigan, Ann Arbor
A. Conway, University of Massachusetts Amherst
S. Corrodi, Argonne National Laboratory
L. Cotrozzi, Istituto Nazionale di Fisica Nucleare, Sezione di Pisa
J. D. Crnkovic, Brookhaven National Laboratory
S. Dabagov, INFN, Laboratori Nazionali Di Frascati
P. T. Debevec, University of Illinois Urbana-Champaign

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The Fermi National Accelerator Laboratory (FNAL) Muon g-2 Experiment has measured the anomalous precession frequency aμ(gμ-2)/2 of the muon to a combined precision of 0.46 parts per million with data collected during its first physics run in 2018. This paper documents the measurement of the magnetic field in the muon storage ring. The magnetic field is monitored by systems and calibrated in terms of the equivalent proton spin precession frequency in a spherical water sample at 34.7C. The measured field is weighted by the muon distribution resulting in ωp′, the denominator in the ratio ωa/ωp′ that together with known fundamental constants yields aμ. The reported uncertainty on ωp′ for the Run-1 data set is 114 ppb consisting of uncertainty contributions from frequency extraction, calibration, mapping, tracking, and averaging of 56 ppb, and contributions from fast transient fields of 99 ppb.

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