Analysis ofY0*(1520) and Determination of theΣParity

Abstract

The interaction of $K^{-}$ mesons on protons resulting in elastic and charge-exchange scattering and hyperon production are reported for a range of momenta from 250 to 513 MeV/c. About 10 000 events obtained in the Lawrence Radiation Laboratory's 15-in. bubble chamber were analyzed. Differential and total cross sections for all channels are examined. For ${\Sigma }^{+}{\pi }^{-}$, ${\Sigma }^0{\pi }^0$, and $\Lambda {\pi }^0$ production, polarization measurements are also available. A resonant state is identified with a mass 1519 MeV and a full width $\Gamma =16\mathrm{}$ MeV, decaying into $\overline{K}N$, $\Sigma \pi$, and $\Lambda \pi \pi$ in the branching ratio 30:55:15, respectively. The resonance is found to have isotopic spin 0 and spin $\frac{3}{2}$, and its parity is that of the $\overline{K}N$ $D_{\frac{3}{2}}$ state. By use of the polarization arising from the $D_{\frac{3}{2}}-S$-wave interference, a strong argument for negative $\mathrm{KN}\Sigma$ parity is obtained. All the data are fitted to a model based on a Breit-Wigner resonant amplitude and nonresonant $S$, $P$, and $D$ amplitudes, parametrized by constant scattering lengths. An extensive search for ${\chi }^2$ minima was done on an IBM-7090 computer under various assumptions for the spin and parity of the resonance. Only the $D_{\frac{3}{2}}$ possibility in both $K^{-}p$ and $\Sigma \pi$ states yields a satisfactory (43% probability) fit. A $D_{\frac{5}{2}}$ $K^{-}p$ resonance (with $\Sigma \pi$ in $F_{\frac{5}{2}}$) is the nearest alternative possibility, with a likelihood of less than 1% of fitting the data.