The Hadronic Light-by-Light Contribution to the Muon Anomalous Magnetic Moment: Where do we stand?

Abstract

We review the status of the hadronic light-by-light contribution to the muon anomalous magnetic moment and critically compare recent calculations. We also study in detail which momentum regions the pi^0 exchange main contribution originates. We also argue that a_\mu^{light-by-light} = (11 \pm 4) \times 10^{-10} encompasses the present understanding of this contribution and comment on some directions to improve on that.

Comments: 16 pages, 9 figures