Analysis of the hadronic light-by-light contributions to the muon g − 2 Original Research Article

We calculate the hadronic light-by-light contributions to the muon g − 2. We use both 1/Nc and chiral counting to organize the calculation. Then we calculate the leading and next-to-leading order in the 1/Nc expansion low energy contributions using the Extended Nambu-Jona-Lasinio model as hadronic model. We do that to all orders in the external momenta and quark masses expansion. Although the hadronic light-by-light contributions to muon g − 2 are not saturated by these low energy contributions we estimate them conservatively. A detailed analysis of the different hadronic light-by-light contributions to muon g − 2 is done. The dominant contribution is the twice anomalous pseudoscalar exchange diagram. The final result we get is aμlight-by-light = (−9.2 ± 3.2) × 10−1. This is between two and three times the expected experimental uncertainty at the forthcoming BNL muon g − 2 experiment.