Peter Arnold

University of Virginia

The QCD Landau-Pomeranchuk-Migdal effect


When a charged, high-energy particle travels through matter, it loses energy by cascading through bremsstrahlung and pair creation. At high enough energies, the coherence time for bremsstrahlung emission becomes large enough that successive collisions can no longer be treated as independent, leading to a reduction of the bremsstrahlung rate known as the Landau-Pomeranchuk-Migdal (LPM) effect. I will give a simple picture of the origin of the LPM effect and explain the difference between the effect in QED and QCD. Then I use the picture to explain the resolution of a theoretical puzzle concerning the role of the LPM effect at very high energies in a finite medium, related to a theoretically idealized picture of high-energy jet energy loss in a quark-gluon plasma created by a heavy ion collision.


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