Nikita Blinov

Electroweak Baryogenesis from Exotic Electroweak Symmetry Breaking

We investigate scenarios in which electroweak baryogenesis can occur during an exotic stage of electroweak symmetry breaking in the early Universe. This transition is driven by the expectation value of a new electroweak scalar instead of the standard Higgs field. A later, second transition then takes the system to the usual electroweak minimum, dominated by the Higgs, while preserving the baryon asymmetry created in the first transition. We discuss the general requirements for such a two-stage electroweak transition to be suitable for electroweak baryogenesis and present a toy model that illustrates the necessary ingredients. We then apply these results to construct an explicit realization of this scenario within the inert two Higgs doublet model. Despite decoupling the Higgs from the symmetry-breaking transition required for electroweak baryogenesis, we find that this picture generically predicts new light states that are accessible experimentally.

Confronting the moduli-induced lightest-superpartner problem

Nikita Blinov, 2, ∗ Jonathan Kozaczuk, † Arjun Menon, ‡ and David E. Morrissey § Theory Department, TRIUMF, 4004 Wesbrook Mall, Vancouver, BC V6T 2A3, Canada Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1, Canada Department of Physics, University of Oregon, Eugene, OR 97403, USA Abstract Moduli fields with Planck-suppressed couplings to light species are common in string compactifications. Decays of these moduli can reheat the universe at a late time and produce dark matter nonthermally. For generic moduli fields motivated by string theory with masses similar to that of the gravitino and TeV-scale superpartners in the minimal supersymmetric Standard Model (MSSM), the non-thermal production of the lightest superpartner (LSP) tends to create an unacceptably large relic density or too strong of an indirect detection signal. We call this the moduli-induced LSP problem of the MSSM. In this paper we investigate extensions of the MSSM containing new LSP candidates that can alleviate this tension. We examine the viability of this scenario in models with light Abelian and non-Abelian hidden sectors, and symmetric or asymmetric dark matter. In these extensions it is possible, though somewhat challenging, to avoid a moduli-induced LSP problem. In all but the asymmetric scenario, the LSP can account for only a small fraction of the observed dark matter density.

Thermal Dark Matter Below a MeV

We consider a class of models in which thermal dark matter is lighter than a MeV. If dark matter thermalizes with the standard model below the temperature of neutrino-photon decoupling, equilibration and freeze-out cool and heat the standard model bath comparably, alleviating constraints from measurements of the effective number of neutrino species. We demonstrate this mechanism in a model consisting of fermionic dark matter coupled to a light scalar mediator. Thermal dark matter can be as light as a few keV, while remaining compatible with existing cosmological and astrophysical observations. This framework motivates new experiments in the direct search for sub-MeV thermal dark matter and light force carriers.

Solving the wrong hierarchy problem

A bstractMany theories require augmenting the Standard Model with additional scalar fields with large order one couplings. We present a new solution to the hierarchy problem for these scalar fields. We explore parity- and ℤ2

Dark Matter Antibaryons from a Supersymmetric Hidden Sector

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Cosmology and accelerator tests of strongly interacting dark matter

-symmetric theories where the Standard Model Higgs potential has two vacua. The parity or ℤ2

A Thermal Neutrino Portal to Sub-MeV Dark Matter

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