Chemical equilibrium in QCD gas in the early universe

  title={Chemical equilibrium in QCD gas in the early universe},
  author={K. Enqvist and J. Sirkka},
  journal={Physics Letters B},
Abstract We compute the thermally averaged q q -annihilation rate into two and three gluons in the early universe. We show that at very high temperatures q q → ggg represents only a 3% correction to q q → gg . Comparing the annihilation rate to the Hubble rate, corrected for particle interactions in the Standard Model gas, we find that quarks and gluons are not in chemical equilibrium when T ≳ 3 × 1014GeV.