Particle Seminar

Monday, October 15, 2018

Speaker: Alexandre Poulin

Time: 2:30PM -- 3:30PM

Location: HP4351

Title: Modifications to the standard freeze-out picture

Abstract: Although Dark Matter (DM) makes up a significant part of the all the 
energy in the Universe, lack experimental DM measurements means that there is
 no clear path or direction for theorists. Because of this,there are many particle 
physics models and ways to theoretically produce DM, one such mechanism is 
thermal freeze-out. In this scenario, the DM was in thermal contact with the 
Standard Model and decoupled once the rate of reaction became comparable to 
the expansion rate of the Universe. This can be a complicated calculation and 
many approximations are typically made, obscuring the physics when making 
modifications to the standard picture. We will explore the concepts behind 
freeze-out in such a way that generalizations to the standard picture become 
clear, well-motivated path for continued research. We will then go down two such
 path by considering modified expansion rate and will be shown that the results 
are not obtain as simply as one would expect if they were only looking at the 
typical freeze-out equations. Next, we will look at the case with multiple DM  
species as a generalization to the single particle case revealing that general 
interactions between DM species can lead to potentially many important effects.