Evidence of kaon nuclear and Coulomb potential effects on soft K + production from nuclei.

Abstract The ratio of forward K + production on copper, silver and gold targets to that on carbon has been measured at proton beam energies between 1.5 and 2.3 GeV as a function of the kaon momentum p K using the ANKE spectrometer at COSY-Julich. The strong suppression in the ratios observed for p K c may be ascribed to a combination of Coulomb and nuclear repulsion in the K + A system. This opens a new way to investigate the interaction of K + -mesons in the nuclear medium. Our data are consistent with a K + A nuclear potential of V K 0 ≈20MeV at low kaon momenta and normal nuclear density. Given the sensitivity of the data to the kaon potential, the current experimental precision might allow one to determine V K 0 to better than 3 MeV.