  Because of colour confinement, the physical vacuum forms an event horizon for
quarks and gluons; this can be crossed only by quantum tunneling, i.e., through
the QCD counterpart of Hawking radiation by black holes. Since such radiation
cannot transmit information to the outside, it must be thermal, of a
temperature determined by the strong force at the confinement surface, and it
must maintain colour neutrality. The resulting process provides a common
mechanism for thermal hadron production in high energy interactions, from
$e^+e^-$ annihilation to heavy ion collisions. The analogy with black-hole
event horizon suggests a dependence of the hadronization temperature on the
baryon density.
