${\Psi }^{\prime }/\Psi$ ratio in Nucleus-Nucleus Collisions : a Measure for the Chiral Symmetry Restoration Temperature ?

Abstract

We argue that a decrease of the chiral scalar meson mass is responsible for re-creation of ${\Psi }^{\prime }$ from $J/\Psi$ in ultrarelativistic nucleus-nucleus collisions. This causes the charmonium yields to freeze out at temperatures close to the chiral symmetry restoration temperature $T_c$. As a result ${\Psi }^{\prime }/\Psi$ may serve as a thermometer for $T_c$ itself. Results in a detailed reaction model support the conjecture. They show good agreement with recent data of NA38 and NA50 for $J/\Psi$ and ${\Psi }^{\prime }$ production in S on U and Pb on Pb collisions.

Comments: 4 pages revtex including 3 postscript figures