2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/94174We compute the time evolving probability of a Gaussian wave packet to be reflected from a rectangular potential barrier which is perturbed by reducing its height. A time interval is found during which this probability of reflection is enhanced (superarrivals) compared to the unperturbed case. Such a time evolving reflection probability implies that the effect of perturbation propagates across the wave packet faster than its group velocity - a curious form of nonlocality.latex, 6 figuresQuantum Physicstext