KN scattering amplitude revisited in a chiral unitary approach and a possible broad resonance in S = +1 channel

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 plab = 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 plab = 500 MeV/c is a hint of the possible broad resonance of strangeness S = +1.