Improved Standard-Model Prediction for π0 → e+ e-

We present an improved standard-model (SM) prediction for the dilepton decay of the neutral pion. The loop amplitude is determined by the pion transition form factor for pi(0) -> gamma*gamma*, for which we employ a dispersive representation that incorporates both spacelike and timelike data as well as short-distance constraints. The resulting SM branching fraction, Br[pi(0) -> e(+)e(-)] x 10(-8), sharpens constraints on physics beyond the SM, including pseudoscalar and axial-vector mediators.

Automated summary

We present an improved prediction for the dilepton decay of the neutral pion in the standard model. This study sharpens constraints on physics beyond the standard model, including pseudoscalar and axial-vector mediators, by determining the loop amplitude using a dispersive representation.