  In brane world string models with large extra dimensions, there are processes
where fermion and antifermion (or two gluons) can annihilate producing a light
particle (e.g. gluon) carrying transverse momentum and a Kaluza-Klein graviton
or an excited closed string that propagates in the extra dimensions. In high
energy colliders, this process gives a missing momentum signature. We compute
the total cross section for this process within the context of type II
superstring theory in the presence of a D brane. This includes all missing
energy sources for this string theory model up to s=8M_s^2, and it can be used
to put new limits on the string scale M_s.
