The interactions of positive K-mesons with nuclei in photographic emulsion at energies in the region (240÷300) MeV

Abstract

148 m of K+ track have been followed in an unbiassed way and 109 inelastic interactions with emulsion nuclei found. In addition 3 K+-proton scattering events have been found and numerous cases of elastic scattering from emulsion nuclei. The differential cross-section for the elastic scattering has been plotted for three energy intervals and the results compared with those predicted by the optical model for various nuclear well depths. The variation of cross-section with energy for the inelastic events is found to be consistent with isotropy if the Pauli Exclusion Principle is taken into account and the best fit for the experimental points is obtained for a repulsive potential well of 20 MeV. The inelastic events have been analysed on the basis of the statistical model of the nucleus and an attempt has also been made to obtain from the experimental data the angular distribution in the C.M. system of the K-nucleon cross-section. On any reasonable assumption this appears to be peaked backwards. These data also demand a repulsive potential of ~ 20 MeV. The value of the average K-nucleon cross-section within nuclear matter for meson energies between 40 and 120 MeV is 4 mb/nucleon; allowing for the events forbidden by the exclusion principle this implies a cross-section of 6 mb on a free nucleon. Taking Σp = 14 ± 3) mb, it follows that ΣD= (2 ± 2) mb. The ratio of charge exchange events to noncharge exchange events is 20 ± 07 — the value expected in the limit of a vanishingly small interaction in theT = 0 state.