Measurement of the π⁰ electromagnetic transition form factor

We present the result of a measurement of the π 0 electromagnetic transition form factor in the time-like region of momentum transfer. From a data sample of 54 000 π 0 →e + e − γ decays, observed in the SINDRUM I magnetic spectrometer at the Paul Scherrer Institute (Switzerland), we measure a value of the form factor slope a=0.025±0.014 (stat)±0.026 (syst). This value is consistent with both the results of the recent measurement by CELLO (DESY) in the spacelike region, and with the vector-mesondominance prediction of a≃0.03