Study of the 6-Prongedπ+pInteractions at 5 GeV/c

Abstract

As a contribution to the study of high-multiplicity phenomena, we have analyzed 3502 six-charged-prong ${\pi }^{+}p$ interactions observed in a hydrogen bubble chamber; the incident ${\pi }^{+}$ momentum was 5 GeV/c. The total cross section for this multiplicity is $\sigma =1.33\mathrm{}\pm 0.05$ mb, mostly contributed by the following reactions: (A) ${\pi }^{+}p\to p3\mathrm{}{\pi }^{+}2{\pi }^{-}$ (0.40±0.03 mb), (B) ${\pi }^{+}p\to p3\mathrm{}{\pi }^{+}2{\pi }^{-}{\pi }^0$ (0.61±0.04 mb), and (C) ${\pi }^{+}p\to n4\mathrm{}{\pi }^{+}2{\pi }^{-}$ (0.11±0.02 mb). Individual particle momentum distributions, when compared with Lorentz-invariant statistical phase space, display deviations which are rather weak but still quite significant. The ${\rho }^0$ meson is abundantly produced in the first reaction (0.26±0.05 mb). In the second reaction the $\omega$ meson is seen with a comparable cross section (0.26±0.03 mb); ${\chi }^0$ and $\eta$ are also observed (50±20 μb and 100±20 μb, respectively, after correction for neutral decays). For both ${\rho }^0$ and $\omega$ resonances there is indication of spin alignment. $N^{*++}\mathrm{}\left(1236\right)\mathrm{}$ production is quite strong; the rate estimate is made difficult by the presence of distortions of the mass spectrum that are shown to be mostly concerned with the ${\pi }^{+}p$ combinations of low c.m. velocity. It is suggested that the short lifetime of the $N^{*}\mathrm{}\left(1236\right)\mathrm{}$ resonance has some bearing on this effect, which indeed seems to affect also the ${\rho }^0$ and not the longer-lived $\omega$.