Cosmological Searches for the Dark Photon

Hugo Schérer ( Université McGill )

The nature of dark matter is one of the greatest mysteries of modern cosmology, and its measured properties can only be explained by physics beyond the Standard Model (SM). Dark matter could reside in a "dark sector" that contains a "dark photon," a spin-1 gauge boson that would couple weakly to the SM photon. This coupling results in interesting phenomenology in a variety of physical contexts. In my research, I study the astrophysical and cosmological phenomenology of the dark photon, in order to derive bounds on its parameters. I mainly focus on photons with longitudinal polarization, which were previously overlooked but which could turn out to have significant consequences on early universe cosmology. In this talk, I will present an overview of observational evidence for dark matter, with emphasis on cosmological observables from the early universe. I will also discuss the dark photon as part of a well-motivated dark sector, and present some bounds on its parameters from cosmology and astrophysics.