Heavy-ion collisions and a new phase of QED

Abstract

We argue that the “anomalous” narrow peaks, seen in the e +e − spectrum of heavy-ion collisions, at energies near the Coulomb barrier, at GSI, may be due to the fact that the effective coupling of the e +e − system to the coherent EM field of the two nuclei, can be of order one at impact parameters comparable to (or smaller than) the e − Compton wavelength. Is is conceivable that the excitation of a large number of virtual and real pairs within a Compton volume could result in momentum correlations for the e + and e −, or even lead to a “new phase” of QED with a different mass scale for the electron. The presence of similar anomalies in the e +e − spectrum of relativistic, but exclusively coherent, collisions of heavy nuclei, would support this idea and rule out any interpretation based on spontaneous emission from a supercritical QED vacuum. In addition, the use of e +e − interferometry could help in clarifying the crucial point of whether the emitted pairs stem from a new or the well-known phase of QED.