Pion production in5−GeVcperipheral antiproton-emulsion interactions

Abstract

The aim of the present work is to investigate the role of resonances in multiple-pion production in the annihilation and nonannihilation interactions of $5\ensuremath{-}\frac{\mathrm{GeV}}{c}$ antiprotons with the free or quasifree nucleons of emulsion nuclei. The separation of these interactions has been made on the basis of a plot of median angle against impact parameter for individual events. A phenomenological investigation of the following aspects has been made: the average survival probability, multiplicity, inelasticity, azimuthal and c.m. angular distributions, total and longitudinal momenta in the c.m. system, and transverse momentum and its dependence on multiplicity, c.m. angle, and longitudinal momentum. It has been observed that the features of nonannihilation interactions are similar to those of $p\ensuremath{-}N$ interactions at comparable primary energies. It has also been inferred that ${N}^{*}(1238)$ and ${\overline{N}}^{*}(1238)$ are responsible for the production of almost all the pions in nonannihilation events. In the annihilation interactions, dominant production of $\ensuremath{\rho}\ensuremath{-}$ and $\ensuremath{\omega}$-meson resonances has been observed. In the over-all annihilation channels, production of $\ensuremath{\rho}$ seems to be much larger than that of $\ensuremath{\omega}$ and the former appears to be emitted preferentially in the forward and the latter in the backward direction of the c.m. system.