Resonances and the Weinberg--Tomozawa 56-baryon --35-meson interaction

Abstract

Vector meson degrees of freedom are incorporated into the Weinberg-Tomozawa (WT) meson-baryon chiral Lagrangian by using a scheme which relies on spin--flavor SU(6) symmetry. The corresponding Bethe-Salpeter approximation successfully reproduces previous SU(3)--flavor WT results for the lowest-lying s--wave negative parity baryon resonances, and it also provides some information on the dynamics of the heavier ones. Moreover, it also predicts the existence of an isoscalar spin-parity ${\frac{3}{2}}^{-}$ $K^{\ast }N$ bound state (strangeness +1) with a mass around 1.7--1.8 GeV, unstable through $K^{\ast }$ decay. Neglecting d-wave KN decays, this state turns out to be quite narrow ($\Gamma \le 15$ MeV) and it might provide clear signals in reactions like $\gamma p\to {\bar{K}}^{0}p{K}^{+}{\pi }^{-}$ by looking at the three body $p{K}^{+}{\pi }^{-}$ invariant mass.

Comments: Talk given at the IVth International Conference on Quarks an Nuclear Physics, Madrid, June 5th-10th 2006. Minor corrections