Revisiting extremely high energy QED bremsstrahlung in matter

par Omar Elgedawy (École polytechnique)

mercredi 18 févr. 2026, 14:00 → 15:00 Europe/Paris

100/2-A201 - Salle A201 (IJCLab)

Very high energy electrons traversing matter lose energy primarily through bremsstrahlung and pair production, initiating electromagnetic showers. At sufficiently high energies, the formation time of bremsstrahlung exceeds the mean free time for elastic scattering in the medium, leading to a suppression of radiation known as the Landau–Pomeranchuk–Migdal (LPM) effect. In this talk, I revisit the LPM suppression of bremsstrahlung and examine how it is modified by quantum overlap with subsequent pair production. I show that, at extremely high energies, pair production can occur within the bremsstrahlung formation time, leading to sizable corrections to the standard LPM picture. Contrary to early qualitative expectations that such effects would further suppress radiation, I find that quantum interference between bremsstrahlung and pair production instead leads to a substantial enhancement of the bremsstrahlung rate relative to the conventional LPM result.