Single-pole nature of the detectable Lambda(1405)

Abstract

We have investigated the single-pole nature of the detectable |$\Lambda(1405)$| in detail, by employing a chiral model having double poles of a |$\bar KN$|–|$\pi \Sigma$| 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 |$T_{\pi \Sigma \leftarrow \bar KN}$|(⁠|$T_{21}$|⁠) and |$T_{\pi \Sigma \leftarrow \pi \Sigma}$|(⁠|$T_{22}$|⁠) 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 |$\Lambda(1405)$|⁠.