The Resolution of the
Anomalous Magentic Moment Result of the Muon

At the beginnin of last year (2001), Brookhaven National Laboratory announced that it had revealed a flaw in the Standard Model of Particle Physics. The lab had measured the anomalous magnetic moment of the muon and found its value to disagree with theory. In its original report, Jupiter Scientific criticized the way newspapers had reported the result because they overemphasized its significance.
     The discrepancy has now been resolved. It turns out that theorists had made a mistake in their calculations. The sign of a contribution coming from the pion, known as the pion pole term, was incorrect. The pion is a short-lived subnuclear particle made from a u or d quark and an anti- u or d quark. Such quark – anti-quark bound states are known as mesons, of which the pion is the lightest weighing about 1/6th the mass of a proton. On April 5, 2002, Physical Review D published the work of Marc Knecht and Andreas Nyffeler revealing the sign error. After correcting the theoretical value, one finds that experiment and theory are in agreement. Case closed!

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