Hadronic light-by-light contribution to muon g-2 in chiral perturbation theory -: art. no. 041601

We compute the hadronic light-by-light scattering contributions to the muon anomalous magnetic moment, a(mu)(LL)(had) , in chiral perturbation theory that are enhanced by large logarithms and a factor of N-C . They depend on a low-energy constant constrained by eta-->mu(+)mu(-) and pi(0)-->e(+)e(-) branching ratios. However, the dependence of a(mu)(LL)(had) on nonlogarithmically enhanced effects cannot be constrained except through the measurement of the anomalous moment itself.