Measurement of the Negative Muon Anomalous Magnetic Moment to 0.7 ppm

TL;DR

The anomalous magnetic moment of the negative muon has been measured to a precision of 0.7 ppm (ppm) at the Brookhaven Alternating Gradient Synchrotron, and is over an order of magnitude more precise than the previous measurement.

Abstract

The anomalous magnetic moment of the negative muon has been measured to a precision of 0.7 parts per million (ppm) at the Brookhaven Alternating Gradient Synchrotron. This result is based on data collected in 2001, and is over an order of magnitude more precise than the previous measurement of the negative muon. The result a_mu= 11 659 214(8)(3) \times 10^{-10} (0.7 ppm), where the first uncertainty is statistical and the second is sytematic, is consistend with previous measurements of the anomaly for the positive and negative muon. The average for the muon anomaly a_{mu}(exp) = 11 659 208(6) \times 10^{-10} (0.5ppm).

Figures (4)

• Figure 1: A two-dimensional multipole expansion of the 2001 field averaged over azimuth from one out of 20 trolley measurements. Half ppm contours with respect to a central azimuthal average field $B_0 = 1.451\,269\,\text{T}$ are shown. The multipole amplitudes relative to $B_0$ are given at the beam aperture, which had a radius of 4.5 cm and is indicated by the circle.
• Figure 2: The Fourier spectrum of the residuals of a fit to the five free parameters given in Eq. \ref{['eq:spectrum']} for the high (top) and low (bottom) $n$-value data. The corresponding CBO frequencies, located at 491 kHz (top), and 419 kHz (bottom) as well as their $(g-2)$ sidebands are clearly visible. Dashed lines indicate the $(g-2)$ frequency.
• Figure 3: Comparison of the $\omega_a$ values from the five analyses for the low-$n$ (filled) and high-$n$ (open) data sets. Analysis 4 used only the combined low and high-$n$ data (square). The divisions on the vertical axis are separated by 1 ppm, and the indicated uncertainties are statistical. The systematic uncertainties are considerably smaller.
• Figure 4: Measurements of $a_\mu$ by E821 with the SM predictions (see text for discussion). Uncertainties indicated on the measurements are total uncertainties.