An evaporating black hole in the presence of an extra spatial dimension would undergo an explosive phase of evaporation. We show that such an event, involving a primordial black hole, can produce a detectable, distinguishable electromagnetic pulse, signaling the existence of an extra dimension of size $Lsim10^{-18}-10^{-20}$ m. We derive a generic relationship between the Lorentz factor of a pulse-producing fireball and the TeV energy scale. For an ordinary toroidally compactified extra dimension, transient radio-pulse searches probe the electroweak energy scale ($sim$0.1 TeV), enabling comparison with the Large Hadron Collider.
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