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Properties of K * ( 890 ) and K * <mml:mn…

1968; American Institute of Physics; Volume: 166; Issue: 5 Linguagem: Inglês

10.1103/physrev.166.1317

1536-6065

F. Schweingruber, M. Derrick, T. Fields, David J. Griffiths, L. Hyman, R. J. Jabbur, J. Loken, R. Ammar, R. Davis, W. Kropac, J. Mott,

Nuclear physics research studies

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.