Improved Standard-Model Prediction for π⁰ → e⁺ e^-and Constraints on BSM Physics

We present the recent work on an improved Standard-Model prediction for the rare decay π⁰ → e⁺ e^-, which plays a crucial role in the test of the long-distance dynamics of the strong interaction. The reduced amplitude of the decay is determined by the pion transition form factor for π⁰ → γ*γ*, for which we employ a dispersive representation that incorporates both time-like and space-like data as well as short-distance constraints. The resulting SM branching fraction, Br[π⁰ → Y*Y*]=6.25(3)×10^-8, reveals a ten-fold improvement in precision over experiment and sharpens constraints on physics beyond the Standard Model.