Resonance production by energetic pions in hydrogen

Abstract

An experiment has been described in which the interactions of positive pions in a hydrogen bubble chamber have been examined. Four lines of investigation have been followed. 1. The general behaviour of interactions in which four positively charged secondary particles are produced has been described. The cross-sections for these interactions and for different final states have been measured, and these have been found to be in reasonable agreement with these founding other experiments at different incident pion momentum. An examination has been made of the resonance production in reactions leading to the most common final states. Again, the results are in agreement with those from other experiments. 2. The quasi-two-body interaction :- π(^+) →N (→pπ(^+), pº(→π(^+)π(^-) π(^+) N (→pπ(^+), wº(→π(^+)π(^-)πº have been studied using the Gottfried-Jackson method of analysis. The spin density matrix elements obtained in this experiment are in agreement with the absorption model ion the first of those reactions, but in poor agreement for the second reaction, as has also been found in other experiments. The decay angular distribution of the B(^+) meson has been examined. He observed distribution is consistent with J(^P) assignment of 1(^+). 4. Different decay mode of the A (_2) meson have been observed, and a sample of two pronged events with at least one visible Vº decay was examined in order to observe the KK decay mode. The observed branching ratios are in agreement with those observed n other experiment. The recent suggestion that there may be more than one resonance with a mass in the region of the A(_2) mass has been investigated by examining the pn and the KK decay modes of the A(_2) separately. The observed characteristics of the two decay modes is consistent with the assumption that only one meson exists with mass in the region of 1.3 GeV/c(^2).