Magnetic Field Measurement and Analysis for the Muon g-2 Experiment

TL;DR

This paper details the hardware and methods used to measure and analyze the magnetic field in the Muon g-2 Experiment at Fermilab, aiming to improve the precision of muon magnetic anomaly measurements.

Contribution

It introduces a comprehensive magnetic field measurement system with in-vacuum NMR probes and calibration techniques for the Muon g-2 Experiment.

Findings

Implementation of in-vacuum NMR probes for precise field measurement

Progress in data analysis from Run-1 and improvements in Run-2

Enhanced calibration methods for magnetic field probes

Abstract

The Muon g-2 Experiment (E989) at Fermilab measures the muon magnetic anomaly, aiming to resolve the greater than 3$\sigma$ discrepancy between the previous measurement and the Standard Model calculation with an improved precision of 140 part-per-billion (ppb). In E989, the muon beam is stored in a ring magnet. The spin precession frequency $\omega_{a}$ is measured by counting the decay positrons in 24 calorimeters, and the magnetic field is measured by nuclear magnet resonance (NMR) probes. An in-vacuum field scanning system consisting of NMR probes and read-out electronics has been implemented to measure the magnetic field applied to the muon beam. An additional 378 NMR probes, placed at fixed locations outside the vacuum chamber, monitor the field drift in between field scans. A high-accuracy probe was designed for calibrating the probes in the scanner. In this presentation, the magnetic field measurement hardware system and analysis methods will be described in detail. The progress of the Run-1 data analysis and improvements in Run-2 will be presented as well.