Comprehensive application of a coupled-channel complex scaling method to the (K)over-bar N-π Y system

We have applied the coupled-channel complex scaling method (ccCSM) to (K) over bar N-pi Y system. One advantage of ccCSM is that resonant states as well as scattering states can be treated in the same framework. For the interactions in the system, we have constructed a meson baryon potential-matrix by basing on the chiral SU(3) theory and respecting the (K) over bar N scattering length obtained in the Martin's analysis. For future purpose to apply it more complicated system such as (K) over bar N N, we adopt a local Gaussian form in the r-space. We have investigated both the non-relativistic (NR) and the semi-relativistic (SR) kinematics. In the SR case, two types of the potentials are obtained. To test the constructed potentials, we have calculated scattering amplitudes and searched resonances. One resonance pole, corresponding to Lambda(1405), is found in isospin I = 0 system around (1419, -20) MeV ((1425, -25) or (1419, -13) MeV) on complex-energy plane with the NR (SR) kinematics. Mean distance between meson and baryon in the resonant state is 1.3 - i0.3 fm (1.2 - i0.5 fm) for NR (SR), in which the states are treated as Gamow states. In addition, we have observed a signature of another pole in lower-energy region involving large decay width, although they are unstable against the change of scaling angle theta. This may correspond to the lower pole of the double-pole of Lambda(1405) discussed in literature today. (C) 2013 Elsevier B.V. All rights reserved.