Neutral-kaon system in dense matter and heavy-ion collisions

Above a critical matter density the propagating modes of the neutral kaon s ystem are essentially eigenstates of strangeness, but below it they are alm ost complete eigenstates of CP. We estimate the real and imaginary parts of the energies of these modes and their mixing at all densities up to a nucl ear matter density of 2 X 10(14) g/cm(3). In a heavy-ion collision the stro ng interactions create eigenstates of strangeness, and these propagate adia batically until the density has fallen to the critical value, whereupon the system undergoes a sudden transition to (near) eigenstates of CP. We estim ate the critical density to be 20 g/cm(3), and that this density will be re ached about 2 X 10(5) fm/c after the end of the collision. (C) 1999 Publish ed by Elsevier Science B.V. All rights reserved.