The Production of Charged Pions at 180° to the Beam by 340-Mev Protons on Carbon

Abstract

The yield of charged pions at 180°±5° to the beam produced by 340-Mev protons on carbon has been measured, using nuclear emulsion techniques. Nuclear emulsions embedded in copper, aluminum, or Lucite absorber blocks were exposed to magnetically separated positive and negative pions emitted at 180° by graphite targets bombarded in the electrically deflected proton beam of the Berkeley synchrocyclotron. Plates were exposed for a series of pion energies from 9 to 118 Mev. The developed emulsions were examined with a microscope under high magnification and meson track endings were identified and counted. The values of $\frac{d\sigma }{d\Omega \mathrm{dT}}$ as a function of pion energy and the values of $\frac{d\sigma }{d\Omega }$ were calculated for both positive and negative pions. Corrections were made for errors resulting from pion decay in flight, the finite thickness of the target, nuclear interaction of pions in the target and absorber blocks, and background pions. The corrected integrated cross sections are $\frac{d\sigma }{d\Omega }\left({\pi }^{+}\right)=1.77\mathrm{}\pm 0.27\times {10}^{-28\mathrm{}} {\mathrm{cm}}^2/\left(\mathrm{sterad}\mathrm{necleus}\right) \mathrm{and}$ $\frac{d\sigma }{d\Omega }\left({\pi }^{-}\right)=1.90\mathrm{}\pm 0.38\times {10}^{-29\mathrm{}} {\mathrm{cm}}^2/\left(\mathrm{sterad}\mathrm{necleus}\right),$ yielding a positive-negative ratio of 9.3±2.3. An attempt has been made to interpret the positive pion spectrum in terms of existing information on the production of positive pions by protons on hydrogen.