Momentum Dependence of the 180°π−pCharge-Exchange Cross Section

The differential cross sections for ${\pi }^{-}p$ charge exchange at 180° are given as a function of ${\pi }^{-}$ momentum from 1.8 to $6.0 \frac{\mathrm{GeV}}{c}$. Below $4 \frac{\mathrm{GeV}}{c}$ there is a resonancelike structure. Above $4 \frac{\mathrm{GeV}}{c}$ the data are in excellent agreement with a smooth exponential drop. A modification of the Igi model gives a good fit to the data. The momentum dependence of the moduli of the isospin-½ and $\frac{3}{2}$ amplitudes and their relative phase is presented.