  We obtain an exact result for the non-perturbative quark (antiquark)
production rate and its p_T distribution from a constant SU(3) chromo-electric
field E^a with arbitary color index $a$ by directly evaluating the path
integral. Unlike the WKB tunneling result, which depends only on one gauge
invariant quantity |E|, the strength of the chromo-electric field, we find that
the exact result for the p_T distribution for quark (antiquark) production rate
depends on two independent Casimir (gauge) invariants, E^aE^a and
[d_{abc}E^aE^bE^c]^2.
