Total π+π− cross-section for dipion energies above 1.5 GeV

The OPE model is applied to the reaction π−p→ nπ+π−. A sample of 1565 fitted events at an incident momentum of 11 GeV/c has been used to obtain an order-of-magnitude estimate for the elastic and total π+π− cross-sections at ππ masses above 1.5 GeV. The assumption is made that the forward amplitude for ππ elastic scattering is purely imaginary att=0 (where |t|-Δ2(π in − π out − )). The elastic differential cross-section is then extrapolated tot=0 and with the help of the optical theorem the total ππ cross-section is derived for different mass intervals of the ππ system.