  We have investigated the single-pole nature of the detectable Lambda(1405) in
detail, by employing a chiral model having double poles of a KbarN-piSigma
coupled channel T-matrix. The effects of the 1st pole and the 2nd pole on the
observed piSigma mass spectrum in the Lambda(1405) region were analyzed
separately by means of the Generalized Optical Potential. It is concluded that
the 1st pole is responsible for both peak structures seen in the T(piSigma
leftarrow KbarN)(T(21)) and T(piSigma leftarrow piSigma)(T(22)) invariant-mass
spectra, and the 2nd pole due to an energy-dependent chiral interaction
provides continuum amplitudes affecting the shape of peak structures in
experimentally observable spectrum of the Lambda(1405).
