Particle Physics Seminar: Dr. Pouya Asadi, University of Oregon

Despite its remarkable success, the Standard Model of particle physics leaves many open problems and falls short of explaining the origin of all matter - dark and visible - in our universe. Explaining the similarity of the baryonic and dark matter energy densities can be the guiding principle in exploring models beyond the Standard Model. I will develop a mechanism explaining this similarity in the context of the axion dark matter model. Starting from a review of sphaleron dynamics, I derive both (i) the axion-induced contributions to fermion asymmetries and (ii) the back-reaction of these fermion asymmetries on axion fields, which manifests itself as a friction on the axions. This analysis clarifies why the minimal axiogenesis scenario cannot produce the correct dark matter and baryon abundances simultaneously. I then show that introducing a second axion and an additional vector-like dark confining sector - a natural infrared realization in the well-motivated axiverse framework - resolves this tension by providing a distinct source of friction in the axion dynamics. Beyond its cosmological implications, this framework motivates searching for the second axion in the ~eV mass range and predicts complementary collider signatures.