Investigation of the Final StatesK−π−π+π0pandK−π−π+π+nProduced inK−pInteractions at 4.6 and 5.0 BeV/c

Abstract

We have studied the reactions $K^{-}p\to K^{-}{\pi }^{-}{\pi }^{+}{\pi }^{0}p$ and $K^{-}p\to K^{-}{\pi }^{-}{\pi }^{+}{\pi }^{+}n$ at 4.6- and 5.0-BeV/c incident $K^{-}$ momenta. Production cross sections for the $K^{-}{\pi }^{-}{\pi }^{-}{\pi }^{+}{\pi }^{0}p$ state are 0.76±0.09 and 0.93±0.12 mb, and for the $K^{-}{\pi }^{-}{\pi }^{+}{\pi }^{+}n$ state 0.42±0.06 and 0.39±0.07 mb, at 4.6 and 5.0 BeV/c, respectively. The combined sample for the $K^{-}{\pi }^{-}{\pi }^{+}{\pi }^{0}p$ state contains 1305 events. Resonance contributions include: ${\overline{K}}^{*0\mathrm{}}\mathrm{}\left(890\right)\mathrm{}$, (19±3)%; $K^{*-}\mathrm{}\left(890\right)\mathrm{}$, (7.2±1.7)%; ${\Delta }^{++}\mathrm{}\left(1236\right)\mathrm{}$, (14.5±2.5)%; ${\Delta }^{+}\mathrm{}\left(1236\right)\mathrm{}$, (8±3)%; ${\Delta }^0\mathrm{}\left(1236\right)\mathrm{}$, ${\omega }^0\mathrm{}\left(784\right)\mathrm{}$, (14.5±3)%; $\eta \mathrm{}\left(548\right)\mathrm{}$, (3.3±1.3)%; a 1060-MeV $3\pi$ effect identified as the $A_1^{}{}_{}{}^0\mathrm{}\left(1080\right)\mathrm{}$, (10.5±3)%; $A_2^{}{}_{}{}^0\mathrm{}\left(1300\right)\mathrm{}$, (3±1.5)%; ${\rho }^{+}\mathrm{}\left(760\right)\mathrm{}$, (9±2.5)%; ${\rho }^{-}\mathrm{}\left(760\right)\mathrm{}$, (5.5±2)%; and a ∼960-MeV narrow $3\pi$ enhancement, (2.5±1)%. The $A_1^{}{}_{}{}^0$ is produced in this reaction in a way precluding contributions from the Deck effect. A spin-parity analysis for the $A_1^{}{}_{}{}^0$ provides good evidence that the spin-parity is in the sequence $0^{-}$, $1^{+}$, $2^{-}$,.... Our results are consistent with the previously favored $1^{+}$ assignment. We have 701 events in the combined sample for the $K^{-}{\pi }^{-}{\pi }^{+}{\pi }^{+}n$ final state. Contributions to this channel from accepted or suspected resonance states include: ${\overline{K}}^{*0\mathrm{}}\mathrm{}\left(890\right)\mathrm{}$, (29±4)%; ${\Delta }^{-}\mathrm{}\left(1236\right)\mathrm{}$, (17±3)%; ${\Delta }^{+}\mathrm{}\left(1236\right)\mathrm{}$, (7±2)%; and a narrow 960-MeV ${\pi }^{+}{\pi }^{+}{\pi }^{-}$ effect, (6±2)%. Addition of $K^{*}\pi$ and $K\rho$ distributions from both final states corresponding to specific values of $I_3$ provides good evidence for production of $K_A\mathrm{}\left(1320\right)\mathrm{}$ and $K_N\mathrm{}\left(1420\right)\mathrm{}$. A similar treatment of $I_3=\frac{3}{2}\Delta \mathrm{}\left(1236\right)\mathrm{}\pi$ and $N_{\rho }\mathrm{}\left(760\right)\mathrm{}$ distributions indicates an effect near 1820 MeV.