Properties ofK*(890)andK*(1400)Produced inK−pInteractions at 4.1 and 5.5 GeV/c

Abstract

The results presented in this paper were obtained from an analysis of ${K}^{\ensuremath{-}}p$ interactions in the 30-in. hydrogen bubble chamber at the Argonne ZGS using incident ${K}^{\ensuremath{-}}$ beams of momenta 4.1 and 5.5 GeV/c. The $\overline{K}\ensuremath{\pi}N$ final states were studied extensively; the most prominent feature of these is production of the ${K}^{*}(890)$ and ${K}^{*}(1400)$ resonances. The ${\overline{K}}^{0}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}n$ final state was used to measure the branching ratio of the decay of the ${K}^{*}(1400)$ into ${K}^{*}(890)\ensuremath{\pi}$ and $K\ensuremath{\rho}$. Evidence for quasi-two-body production of ${K}^{*}{(890)}^{\ensuremath{-}}$ and ${K}^{*}{(1400)}^{\ensuremath{-}}$ is presented both from the two-prong events in which the positive track was identified as a proton, and from events where the ${\overline{K}}^{0}$ decay was observed. For final states with a missing neutron, a study of the missing-mass distributions proved that the kinematical fits to ${K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}n$ and ${\overline{K}}^{0}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}n$ final states could be used with confidence to study ${K}^{*}{(890)}^{0}$ and ${K}^{*}{(1400)}^{0}$ production. The ${K}^{*}{(890)}^{0,\ensuremath{-}}$ production angular distribution and decay correlations are analyzed in the framework of the absorptive peripheral model. Vector exchange dominates the ${K}^{*}{(890)}^{\ensuremath{-}}$ production, whereas ${K}^{*}{(890)}^{0}$ is formed mainly via pseudoscalar exchange. An absorptive-peripheral-model calculation using the vector-meson coupling strengths to the nucleon given by relativistic $\mathrm{SU}(6)$ gives a good fit to the ${K}^{*}{(890)}^{0,\ensuremath{-}}$ density-matrix elements as a function of production angle, and gives a reasonable fit to the differential cross section. For the ${K}^{*}(1400)$ resonance, a mass and width of 1416\ifmmode\pm\else\textpm\fi{}8 and 107\ifmmode\pm\else\textpm\fi{}20 MeV are obtained. Decay branching ratios measured for this resonance of $K\ensuremath{\pi}:{K}^{*}\ensuremath{\pi}:K\ensuremath{\rho}$ of 1: (0.52\ifmmode\pm\else\textpm\fi{}0.12): (0.26\ifmmode\pm\else\textpm\fi{}0.16) are in agreement with those predicted from $\mathrm{SU}(3)$ assuming the ${K}^{*}(1400)$ is a member of a ${2}^{+}$ nonet. The absorptive peripheral model gives no reasonable fits to the ${K}^{*}(1400)$ production angular distributions. The ${K}^{*}{(1400)}^{0,\ensuremath{-}}$ production and decay angular distributions suggest that the spin parity of the ${K}^{*}(1400)$ is ${2}^{+}$, but without many more events, or a better model for the production mechanism, we cannot make a decisive determination.

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