  Using the AdS/CFT correspondence for strongly coupled gauge theories, we
calculate thermalization of mesons caused by a time-dependent change of a
baryon number chemical potential. On the gravity side, the thermalization
corresponds to a horizon formation on the probe flavor brane in the AdS throat.
Since heavy ion collisions are locally approximated by a sudden change of the
baryon number chemical potential, we discuss implication of our results to RHIC
and LHC experiments, to find a rough estimate of rather rapid thermalization
time-scale t_{th} < 1 [fm/c]. We also discuss universality of our analysis
against varying gauge theories.
