Medium effects in the $ΛK^+$ pair production by 2.83 GeV protons on nuclei

E. Ya. Paryev, M. Hartmann, Yu. T. Kiselev

Published 2016-12-08Version 1

We study the ${\Lambda}K^+$ pair production in the interaction of protons of 2.83 GeV kinetic energy with C, Cu, Ag, and Au target nuclei in the framework of the nuclear spectral function approach for incoherent primary proton--nucleon, secondary pion--nucleon production processes and processes associated with the creation of intermediate ${\Sigma^0}K^+$ pairs. The approach accounts for the initial proton, final $\Lambda$ hyperon and $K^+$ meson absorption in nuclei, target nucleon binding and Fermi motion as well as nuclear mean-field potential effects on these processes. We calculate the $\Lambda$ momentum dependence of the absolute ${\Lambda}K^+$ yield from the considered target nuclei in the kinematical conditions of the ANKE experiment, performed at COSY, within the different scenarios for the $\Lambda$-nucleus optical potential. We show that the above observable is appreciable sensitive to this potential in the low-momentum region. Therefore, it can help to determine the $\Lambda$ hyperon optical potential at finite momenta from the direct comparison of the results of our calculations with the data from the ANKE-at-COSY experiment. We also demonstrate that the two-step pion--nucleon production channels dominate in the low-momentum ${\Lambda}K^+$ production in the chosen kinematics and, therefore, they have to be taken into account in the analysis of these data.