Low-MomentumK−-He4Scattering

We have measured the differential cross section for elastic scattering of $K^{-}$ mesons on ${\mathrm{He}}^4$ in the momentum intervals 100-150 MeV/c and 150-200 MeV/c, and the total inelastic cross section in the interval 150-200 MeV/c. We have calculated scattering lengths for the $K^{-}$-${\mathrm{He}}^4$ system using the zero-effective-range approximation. The results for the scattering lengths have been compared with other experiments, including a measurement of $K^{-}$-mesonic x rays in ${\mathrm{He}}^4$. Our results are in disagreement with the latter.