Energy Spectrum of Thermalizing High Energy Decay Products in the Early Universe [CL]

http://arxiv.org/abs/2105.01935


We revisit the Boltzmann equation governing the spectrum of energetic particles originating from the decay of massive progenitors during the process of thermalization. We assume that these decays occur when the background temperature $T$ is much less than the mass $M$ of the progenitor. We pay special attention to the IR cutoff provided by the thermal bath, and include the suppression resulting from the interference of multiple scattering reactions (LPM effect). We solve the resulting integral equation numerically, and construct an accurate analytical fit of the solutions. Our results indicate that the normalization of the spectrum has previously been underestimated by as much as $\sqrt{M/T}$.

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M. Drees and B. Najjari
Thu, 6 May 21
45/55

Comments: 19 pages + references — 5 figures