Can one measure C-odd asymmetry in e+e−→π+π− ?

C-odd asymmetry can be studied from an accurate measurement of the angular distribution due to the interference between the S- and P-waves in e+e−→π+π− at order α3. Though the integrated total cross-section is zero as expected from the Furry's theorem, the asymmetry is dominated by the pion rescattering diagram which is enhanced by the presence of the , and is quite large (≈11% at θ=30° and ) compared to α/π≃0.3%. This process can also be used for alternatively measuring the size of the rescattering term and the phase of the S-wave amplitude, but does not help to solve the present discrepancy between the hadronic spectral functions from e+e− and τ-decay data.