Thermal Relaxation Time in Chemically Non-equilibrated Quark- Gluon Plasma

The definition of thermal relaxation time is extended to chemically non-equilibrated quark-gluon plasma and the chemical non-equilibrated thermal relaxation times for partons are calculated using the non-equilibrium Debye mass as the infrared regulator. The dependence of the thermal relaxation time on the fugacity is given and the influence of the chemical non-equilibration is discussed. We find that there are threshold fugacities $\lambda_g^*$ and $\lambda_q^*$ for gluons and quarks. For \lambda_g < \lambda_g^* (\lambda_q < \lambda_q^*), \tau_g^{NEQ}/\tau_g^{EQ} (\tau_q^{NEQ}/\tau_q^{EQ}) decreases strongly with increasing fugacity, while for $\lambda_g > \lambda_g^* (\lambda_q>\lambda_q^*$), the ratios are almost 1. It is shown that there is also the two-stage equilibration in a chemically non-equilibrated plasma. We also discussed the effect of using the non-equilibrium Deby mass as the infrared cutoff.