Cosmological implications of a U(1) extension of the Standard Model

Thursday 8 Dec 2022, 15:15 → 17:15 Europe/Stockholm

The Standard Model of particle physics is known to have shortcomings when it comes to certain observations. In particular, astrophysical measurements have indicated the existence of an unknown type of feebly interacting matter (which we generally call dark matter), as well as significant asymmetry between the number of baryons and anti-baryons. In this talk, I will introduce a simple U(1) extension with particular focus on simultaneously explaining these cosmological observations. Right-handed neutrinos are introduced to account for the finite mass of the neutrinos, and furthermore their lightest member can be our dark matter particle. The dark matter study constrains the masses of the particles involved and provides us with a range for the vacuum expectation value of a new singlet scalar, that acts as the Higgs in the dark sector. Given these parameters, the effective potential of the 2-scalar system can be calculated and we can find the nature of the phase transition. The effective potential is known to be complex below the zero temperature minimum: this feature is unphysical and is usually dropped in calculations. In the second part of my talk, I will present a novel, consistent way of obtaining a fully real effective potential.

Lund_Seminar_2022_December.pdf