Abstract
Abstract We revisit the $KN$ scattering amplitude in order to investigate the possibility of the existence of a broad resonance in the $I=0$$KN$ channel around the energy of 1617 MeV with 305 MeV width. We use the chiral unitary model to describe the $KN$ scattering amplitudes and determine the model parameters so as to reproduce the differential cross sections of the $K^{+}N$ scatterings and the $I=0$ and 1 total cross sections up to $p_{\rm lab} = 800$ MeV/c, from which inelastic contributions start to be significant. Performing analytic continuation of the determined amplitude to the complex energy plane, we find a pole for a broad resonance state. We point out that the rapid increase appearing in the $I=0$ total cross section around $p_{\rm lab}=500$ MeV/c is a hint of the possible broad resonance of strangeness $S=+1$.
Highlights
The study of meson-baryon scattering is very important to understand the properties of hadron resonances
Once we parametrize the scattering amplitude in an analytic function, analytic continuation allows us to extend the amplitude to the complex energy plane, where resonances are represented as poles, and extract the properties of resonances, such as mass, decay width and coupling strength
In the chiral unitary approach, the interaction kernel V is given by chiral perturbation theory and we restrict the intermediate state to the elastic channel
Summary
The study of meson-baryon scattering is very important to understand the properties of hadron resonances. We reexamine the elastic scattering amplitude of KN in low energies, plab < 800 MeV/c, based on the chiral unitary approach and study the possibility of an S = +1 exotic resonance in I = 0 channel. The phase shift analysis by Martin [11] found that there were no significant resonances in the partial wave amplitude, the Argand diagram suggested that there could be some broad resonances appearing in P01 and D03 [20,21,22]. These resonances were reported as broad resonances above the energies where the inelastic contributions start to be significant.
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