Measurement of the muon anomaly to high and even higher precision

• Published in: Nuclear physics. Section B, Proceedings supplement Vol. 144; pp. 191 - 200
• Main Author: Hertzog, David W.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-07-2005
• ISSN: 0920-5632; 1873-3832
• DOI: 10.1016/j.nuclphysbps.2005.02.027

Our recent series of measurements at Brookhaven National Laboratory determined the muon anomalous magnetic moment
α
μ
to a precision of 0.5 ppm. The final result—representing the average of five running periods using both positive and negative muons—is
α
μ
±
=
11
659
208
(
6
)
×
10
−10
. It lies 2.7 standard deviations above the standard model expectation, which is based on updates given at this Workshop. Importantly, only the
e
+
e
−
annihilation and new KLOE radiative return data are used for the hadronic vacuum polarization input. Because the systematic limit has not been reached in the experiment, a new effort has been proposed and approved with the highest scientific priority at Brookhaven. The goal is an experimental uncertainty of 0.2 ppm, a 2.5-fold reduction in the overall experimental uncertainty. To do so will require a suite of upgrades and several qualitative changes in the philosophy of how the measurement is carried out. I discuss the old and new experiments with a particular emphasis on the technical matters that require change for the future.