Charge-Exchange Scattering of Negative Pions at 61 Mev and 95 Mev

The charge-exchange scattering of negative pions by liquid hydrogen has been measured at 61±1 Mev and 95±2 Mev bombarding energy. The measurements were made with a gamma-ray spectrometer which employs a lead glass Čerenkov counter. If the charge exchange scattering cross section is expanded as a series of Legendre polynomials in the center-of-mass system of the collision, we find that at 61 Mev, $\frac{d\sigma }{d\Omega }=(1.00\mathrm{}\pm 0.05)[0.613\pm 0.030-(0.830\pm 0.068\left)P_1\right({cos\theta }^{\prime })+(0.183\mathrm{}\pm 0.150\left)P_2\right({cos\theta }^{\prime }\left)\right],$ and at 95 Mev, $\frac{d\sigma }{d\Omega }=(1.00\mathrm{}\pm 0.03)[1.05\pm 0.05-(1.15\pm 0.12\left)P_1\right({cos\theta }^{\prime })+(0.33\mathrm{}\pm 0.25\left)P_2\right({cos\theta }^{\prime }\left)\right].\mathrm{}$ The total cross section for charge exchange, obtained by integration, is: ${\sigma }_{\mathrm{tot}}({\pi }^{-}\to {\pi }^0)=7.7\mathrm{}\pm 0.6$ mb at 61 Mev and ${\sigma }_{\mathrm{tot}}({\pi }^{-}\to {\pi }^0)=13.2\mathrm{}\pm 0.8$ mb at 95 Mev.