Eur. Phys. J. A 9, 521-536
Antikaon production and medium effects in proton-nucleus reactions at subthreshold beam energies
Institute for Nuclear Research, Russian Academy
of Sciences, Moscow 117312, Russia
Received: 20 July 2000 / Revised version: 10 November 2000
Communicated by W. Weise
Abstract
The inclusive K--meson production in proton-nucleus
collisions in the subthreshold energy regime is analyzed in the
framework of an appropriate folding model for incoherent primary
proton-nucleon and secondary pion-nucleon production processes,
which takes properly into account the struck target nucleon
momentum and removal energy distribution (nucleon spectral
function), novel elementary cross-sections for proton-nucleon
reaction channel close to threshold as well as nuclear mean-field
potential effects on the one-step and two-step antikaon creation
processes. A detailed comparison of the model calculations of the
K- differential cross-sections for the reactions
p +
and p +
at subthreshold
energies with the first experimental data obtained at the ITEP
proton synchrotron is given, that displays both the relative role
of the primary and secondary production channels at considered
incident energies and the contributions to the K- production
coming from the use of the single-particle part as well as high-momentum-energy
part of the nucleon spectral function. It is
found that the pion-nucleon production channel does not dominate
in the subthreshold ``hard'' antikaon production in
p
-, p
-collisions and the
main contributions to the antikaon yields here come from the
direct K- production mechanism. The influence of the nucleon,
kaon and antikaon mean-field potentials on the K- yield is
explored. It is shown that the effect of the nucleon mean-field
is of importance in explaining the considered experimental data
on ``hard'' antikaon production, whereas the K+ and K-optical potentials play a minor role. The sensitivity of the
subthreshold ``soft'' antikaon production in p
-,
p
-reactions to the nucleon, kaon and antikaon
mean fields is studied. It is demonstrated that, contrary to the
case of ``hard'' antikaon production, the K- potential has a
very strong effect on the K- yield, which is greater than that
from nucleon effective potential.
PACS
25.40.-h Nucleon-induced reactions
Copyright Società Italiana di Fisica, Springer-Verlag 2000
