Kaonic hydrogen atom and low energyK¯Ninteraction

The apparent discrepancy between the ${\mathit{K}}^{\mathrm{-}}$p scattering length obtained from the 1S level shift of the kaonic hydrogen atom and that from the K¯N scattering at low energies is reexamined. Two models, one proposed by Kumar and Nogami and the other by Schnick and Landau, are extended by including all relevant channels so that comparison with all data available at low energies is possible. A value of the ${\mathit{K}}^{\mathrm{-}}$p scattering length consistent with the atomic data and a good overall fit to all the other low energy data have been obtained by means of the extended Schnick-Landau model. The resulting ${\mathit{K}}^{\mathrm{-}}$p scattering amplitude is quite different from the one determined earlier by means of the K-matrix parametrization. Its sign around threshold is opposite to that indicated by the low energy extrapolation of the Coulomb-nuclear interference data. It is argued that the extrapolation is subject to some uncertainty.