π−−pInteractions at 1.3 Bev

Abstract

A study has been made of the interactions of 1.3-Bev ${\pi }^{-}$ mesons from the Cosmotron in the Columbia 12-in. propane bubble chamber. Out of a total of 1401 two-prong interactions measured and analyzed, 587 were classified as hydrogen interactions. Techniques used in scanning, measurement, and analysis, and the uncertainties involved in these techniques are discussed with special reference to the problem of carbon contamination. Corrections to the data are calculated. Best values for cross sections at this energy are: ${\sigma }_{\mathrm{el}}=10.5\mathrm{}\pm 0.8$ mb, ${\sigma }_{{\pi }^{-}{\pi }^{+}n}=9.2\mathrm{}\pm 1.4$ mb, ${\sigma }_{{\pi }^{-}\pi 0p}=6.2\mathrm{}\pm 0.9$ mb, ${\sigma }_{\mathrm{neutral}}=5.2\mathrm{}\pm 0.2$ mb, and ${\sigma }_{{\pi }^{-}{\pi }^{-}{\pi }^{+}p}={{1.0}_{-0.3\mathrm{}}}^{+0.5\mathrm{}}$ mb, normalized to ${\sigma }_{\mathrm{total}}=34.7\mathrm{}\pm 1.2$ mb. A study of ${\pi }^{-}+n\to {\pi }^{-}+{\pi }^{-}+p$ events in carbon is used to provide evidence on carbon contamination in single pion production. The data on single pion production processes are compared in detail with the predictions of the statistical model, the isobar model, and pion-pion interaction theory. The extended isobar model gives qualitative agreement with some features of the c.m. momentum spectra, but quantitative agreement is poor. Evidence is found for a resonance in ${\sigma }_{\pi \pi }\left(\omega \right)$ between 700 and 800 Mev total energy for the dipion system. The data are consistent with a resonance in the $T=J=1\mathrm{}$ $\pi -\pi$ state. A rise in the $\pi -\pi$ cross section at low energies appears to occur. Differences in results for (${\pi }^{-}, {\pi }^{+}, n$) and (${\pi }^{-}, {\pi }^0, p$) events are considered. Evidence for final-state pion-nucleon interactions in conjunction with pion-pion interactions is presented.