SU(6) extension of the Weinberg-Tomozawa meson-baryon Lagrangian

A consistent SU(6) extension of the Weinberg-Tomozawa meson-baryon chiral Lagrangian is constructed which incorporates vector meson and baryon decuplet degrees of freedom. The corresponding Bethe-Salpeter approximation predicts the existence of an isoscalar spin-parity 3^-2 K*N bound state (strangeness $+1$) with a mass around 1.7--1.8 GeV. It is the highest hypercharge state of an antidecuplet SU(3) representation and it is unstable through K* decay. The estimated width of this state (neglecting d-wave $KN$ decay) turns out to be small (Γ≤15 MeV). Clear signals of this resonance would be found in reactions like γp→K̄⁰pK⁺π^- by looking at the three body pK⁺π^- invariant mass.