Quantum and Thermal Fluctuations of Cherenkov Radiation from HQET

Abstract

Charged particles travelling faster than the speed of light in the medium in which they propagate emit Cherenkov radiation. The formula for the spectrum of this radiation as a function of frequency, known as the Frank-Tamm formula, first derived almost 90 years ago, follows purely from classical electromagnetism. In this work, we demonstrate how this result also follows from a short quantum field theory calculation, which in addition to it contains all of the cumulants of thermal and quantum fluctuations around the classical radiation spectrum at leading order in the inverse of the particle's mass. All of these results follow from the particle's momentum change probability, which we calculate for weakly coupled gauge theories using the tools of Heavy Quark Effective theory.