A new measurement of the muon magnetic anomaly

The muon magnetic anomaly may contain contributions from physics beyond the standard model. At the Brookhaven National Laboratory (BNL) a precision experiment aims for a measurement of the muon magnetic anomaly aµ to 0.35 ppm, where conclusions about various theoretical approaches beyond standard theory can be expected. The difference between the spin precession and cyclotron frequencies is measured in a magnetic storage ring with highly homogeneous field. Data taking is in progress and part of all recorded data has been analyzed. Combining all experimental results to date yields preliminarily aµ(expt) = 1 165 921(5) · 10 9 (4 ppm) in agreement with standard theory.