Evidence for two Lambda(1405) resonance states

Abstract

The $K^{-}p\to {\pi }^0{\pi }^0{\Sigma }^0$ reaction is studied within a chiral unitary model. The distribution of ${\pi }^0{\Sigma }^0$ states forming the $\Lambda (1405)$ shows, in agreement with a recent experiment, a peak at 1420 MeV and a relatively narrow width of $\Gamma =38$ MeV. We use these data in combination with those of the ${\pi }^{-}p\to K^0\pi \Sigma$ reaction and elements of chiral unitary theory to prove that there are two $\Lambda (1405)$ states instead of one as so far assumed.

Comments: Contribution to the Hadron05 Conference, Rio de Janeiro, September 2005