The muon anomalous magnetic moment and a new light gauge boson

It is shown that the 2.6 sigma discrepancy between the predicted and recently measured value of the anomalous magnetic moment of positive muons could be explained by the existence of a new light gauge boson X with a mass MX less than or equal to O(5) GeV. Phenomenological bounds on the X coupling are discussed. (C) 2001 Published by Elsevier Science B.V.