Branching ratio change in $K^{-}$ absorption at rest and the nature of the Λ(1405)

We investigate in-medium corrections to the branching ratio in $K^{-}$ absorption at rest and their effect on the charged pion ${\pi }^{\pm }$ spectrum. The in-medium corrections are due to Pauli blocking, which arises if the Λ(1405) is assumed to be a $\overline{K}$-nucleon bound state and leads to a density- and momentum-dependent mass shift of the Λ(1405). Requiring that the optical potential and the branching ratio are derived from the same elementary $T$ matrix, we find that the in-medium–corrected, density-dependent $T$ matrix gives a better description of the $K^{-}$ absorption reaction than the free, density-independent one. This result suggests that the dominant component of the Λ(1405) wave function is the $\overline{K}N$ bound state.