Scattering of 22-Mev Positive Pions by Protons

The differential cross section for the reaction π⁺+p→π⁺+p was measured in the angular interval 45^∘{} to 135^∘{} in the center-of-mass system at a pion energy of 21.5±{}3.5 Mev in the laboratory system. The pion beam was formed by a magnetic-focusing selection of pions produced from polyethylene at an angle of 0^∘{} in the reaction p+p→π⁺+d. The production target was placed in the strong-focused 340-Mev proton beam electrostatically deflected from the Berkeley synchrocyclotron. The pion beam entered liquid hydrogen contained in a Styrofoam scattering target at 25.0 Mev, with an energy spread of ±{}0.6 Mev, and left at 18.0 Mev. Scattered pions were detected in an emulsion stack placed 1 inch from the beam edge and 7/8 inch from the liquid hydrogen. The data, consisting of 41 acceptable events, were analyzed by a maximum-likelihood method to obtain the following best values for the pion-proton scattering phase shifts at a relative momentum, η=0.49:α₃=-0.048±0.007, α₃₃=+0.013±0.013, α₃₁=0.000±0.016.