Single-pole nature of the detectable Lambda(1405)

We have investigated the single-pole nature of the detectable Lambda(1405) in detail, by employing a chiral model having double poles of a <(K)overbar>N-pi Sigma coupled-channel T-matrix. The effects of the first pole and the second pole on the observed pi Sigma mass spectrum in the Lambda(1405) region have been analyzed almost separately. It is concluded that the first pole is responsible for both peak structures seen in the T-pi Sigma <-<(K)overbar>N(T-21) and T-pi Sigma <-pi Sigma(T-22) invariant-mass spectra, and, due to an energy-dependent chiral interaction, the second pole provides continuum amplitudes affecting the shape of the peak structures of the first pole in the experimentally observable spectrum of Lambda(1405).