G-2 of the Muon

Abstract

The experimental value a $_{\mu}^{\rm exp}$ for the muon magnetic anomaly measured at the Brookhaven National Laboratory (BNL), Upton, USA, and the latest theoretical value a $_{\mu}^{\rm theo}$ based on a number of calculations and auxiliary experiments differ today by 3.3 standard deviations. Discrepancies between different independent approaches towards the theoretical value could recently be removed and had yielded a consistent value for a $_{\mu}^{\rm theo}$ . At the Fermi National Laboratory (Fermilab), Batavia, USA, a new experiment has been approved which aims to improve the present experimental uncertainty by a factor of about five. At this level the muon magnetic anomaly is superior in sensitivity to, e.g., LHC concerning tests of several speculative models beyond standard theory. The new experiment relies in the essential parts on concepts proven at BNL such as a muon storage ring at 1.45 T field to store muons at 3.1 GeV/c momentum and field magnetometry based on NMR in water. At Fermilab predominantly a significantly higher number of muons can be exploited.