Nature ofΛ(1405)

We study the structure of $\Lambda \mathrm{}\left(1405\right)\mathrm{}$ by means of a coupled-channel potential model and by fitting low-energy $\overline{K}N$ data, including the $K^{-}p$ scattering length obtained from the latest x-ray measurements of the kaonic hydrogen atom. From the best fit obtained, we find two possible interpretations of $\Lambda \mathrm{}\left(1405\right),$ either as (1) the ${70}^{-}$ three-quark state strongly coupled with $\overline{K}N$ and $\pi \Sigma$ or (2) a $\pi \Sigma$ resonance and/or an unstable $\overline{K}N$ bound state. In the latter case, the three-quark state that belongs to the ${70}^{-}$ multiplet is located slightly above the $\overline{K}N$ threshold and results in a sharp resonance peak in the $K^{-}p$ elastic cross section at laboratory momentum $170\hspace{0.5em}\mathrm{MeV}/c.\mathrm{}$ To explore these possibilities, measurements of the $\pi \Sigma$ invariant mass distribution and the $K^{-}p$ cross sections with finer resolution are required.