Neutral Kaon System in Dense Matter and Heavy-Ion Collisions

TL;DR

This paper investigates how the neutral kaon system's eigenstates change with matter density, highlighting a transition from strangeness eigenstates to CP eigenstates around a critical density relevant in heavy-ion collisions.

Contribution

It provides a detailed estimation of the energies and mixing of neutral kaon modes across a range of densities up to nuclear matter density, and models their behavior in heavy-ion collisions.

Findings

Critical density for transition is approximately 20 g/cm^3.

Transition occurs about 2×10^5 fm/c after collision.

Eigenstates shift from strangeness to CP eigenstates at critical density.

Abstract

Above a critical matter density the propagating modes of the neutral kaon system are essentially eigenstates of strangeness, but below it they are almost 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 nuclear matter density $2\times 10^{14}$ g/cm$^3$. In a heavy ion collision the strong interactions create eigenstates of strangeness, and these propagate adiabatically until the density has fallen to the critical value, whereupon the system undergoes a sudden transition to (near) eigenstates of CP. We estimate the critical density to be 20 g/cm$^3$, and that this density will be reached about $2\times 10^5$ fm/c after the end of the collision.