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تسجيل مستخدم جديدImproved Standard-Model prediction for $pi^0to e^+e^-$
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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 $pi^0togamma^*gamma^*$, for which we employ a dispersive representation that incorporates both space-like and time-like data as well as short-distance constraints. The resulting SM branching fraction, $ text{BR}(pi^0to e^+e^-)=6.25(3)times 10^{-8}$ , sharpens constraints on physics beyond the SM, including pseudoscalar and axial-vector mediators.
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