Tracking Fast Small Color Dipoles through Strong Gluon Fields at the LHC

We argue that the process gamma + A -> J/psi + gap + X at large momentum transfer q(2) provides a quick and effective way to test the onset of a novel perturbative QCD regime of strong absorption for the interaction of small dipoles at the collider energies. We find that already the first heavy-ion run at the LHC will allow one to study this reaction with sufficient statistics via ultraperipheral collisions, hence probing the interaction of q (q) over bar dipoles of sizes similar to 0.2 fm with nuclear media down to x similar to 10(-5).