Study ofK¯N→YπbelowK¯NThreshold and the Dynamical Nature of theY0*(1405)

Abstract

We have studied the $Y\pi$ angular distributions for the reaction $K^{-}d\to Y\pi N$ for the $Y\pi$ mass range 1350-1530 MeV. These data are used to study the $\overline{K}N\to Y\pi$ amplitudes below $\overline{K}N$ threshold. The analysis confirms previous SU(3) multiplet assignments for the $\Lambda \mathrm{}\left(1520\right)\mathrm{}$ and $\Sigma \mathrm{}\left(1385\right)\mathrm{}$, and indicates that the $S_{01}$ channel is dominated by a repulsive background with the $\Lambda \mathrm{}\left(1405\right)\mathrm{}$ being a small effect superimposed on the background. This conclusion is at odds with the usual $K$-matrix analysis of the low-energy $\overline{K}N$ data but is somewhat supported by recent evidence from baryon-exchange production of the $\Lambda \mathrm{}\left(1405\right)\mathrm{}$.