We compute by numerical integration of the Dirac equation the number of quark-antiquark pairs initially produced in the classical color fields of colliding ultrarelativistic nuclei. While the number of $q\overline{q}$ pairs is parametrically suppressed in the coupling constant, we find that in this classical field model their production rate is comparable to the thermal ratio of $\mathrm{\text{gluons}}/\mathrm{\text{pairs}}=9N_{\mathrm{f}}/32$. After isotropization one thus would have a quark-gluon plasma in chemical equilibrium.

• Received 23 August 2005

DOI:https://doi.org/10.1103/PhysRevLett.96.032304