Electroweak baryogenesis

171

167

The discovery of the Higgs boson by the LHC experiments ATLAS and CMS has marked a milestone for particle physics. Yet, there are still many open questions that cannot be answered within the Standard Model (SM). For example, the generation of the observed matter-antimatter asymmetry in the universe through baryogenesis can only be explained qualitatively in the SM. A simple extension of the SM compatible with the current theoretical and experimental constraints is given by the 2-Higgs-Doublet Model (2HDM) where a second Higgs doublet is added to the Higgs sector. We investigate the possibility of a strong first order electroweak phase transition in the CP-conserving 2HDM type I and type II where either of the CP-even Higgs bosons is identified with the SM-like Higgs boson. The renormalisation that we apply on the loop-corrected Higgs potential allows us to efficiently scan the 2HDM parameter space and simultaneously take into account all relevant theoretical and up-to-date experimental constraints. The 2HDM parameter regions found to be compatible with the applied constraints and a strong electroweak phase transition are analysed systematically. Our results show that there is a strong interplay between the requirement of a strong phase transition and collider phenomenology with testable implications for searches at the LHC.

Section: Jhep02(2017)121mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Strong first order electroweak phase transition in the CP-conserving 2HDM revisited

Basler

Krause

Mühlleitner

et al. 2017

171

167

“…To obtain an explicitly gauge-invariant result, 3 we will also analyze the finite-T behavior of the model by retaining only the tree-level potential at T = 0, performing a high-T expansion of the thermal functions, whereby…”

Section: Jhep08(2017)096mentioning

confidence: 99%

Non-resonant collider signatures of a singlet-driven electroweak phase transition

Chen

Kozaczuk

Lewis

2017

107

Abstract:We analyze the collider signatures of the real singlet extension of the Standard Model in regions consistent with a strong first-order electroweak phase transition and a singlet-like scalar heavier than the Standard Model-like Higgs. A definitive correlation exists between the strength of the phase transition and the trilinear coupling of the Higgs to two singlet-like scalars, and hence between the phase transition and non-resonant scalar pair production involving the singlet at colliders. We study the prospects for observing these processes at the LHC and a future 100 TeV pp collider, focusing particularly on double singlet production. We also discuss correlations between the strength of the electroweak phase transition and other observables at hadron and future lepton colliders. Searches for non-resonant singlet-like scalar pair production at 100 TeV would provide a sensitive probe of the electroweak phase transition in this model, complementing resonant di-Higgs searches and precision measurements. Our study illustrates a strategy for systematically exploring the phenomenologically viable parameter space of this model, which we hope will be useful for future work.

“…A singlet scalar boson s does not affect the ρ parameter at tree level, and is not that strongly constrained by the electroweak precision tests (EWPT). It can also make the electroweak phase transition strongly first order [33,34], and enables us to consider electroweak baryogenesis if there are new sources of CP violation beyond the Kobayashi-Maskawa (KM) phase in the SM with three generations. Finally, if we imposed a new discrete Z 2 symmetry s → −s, the singlet scalar s could make a good dark matter candidate [35][36][37].…”

Section: Modelsmentioning

confidence: 99%

Bounds on Higgs-portal models from the LHC Higgs data

Cheung

Ko²,

Lee

et al. 2015

In a number of Higgs-portal models, an SU(2) isospin-singlet scalar boson generically appears at the electroweak scale and can mix with the Standard Model (SM) Higgs boson with a mixing angle α. This singlet scalar boson can have renormalizable couplings to a pair of dark matter particles, vector-like leptons or quarks, or new gauge bosons, thereby modifying the Higgs signal strengths in a nontrivial way. In this work, we perform global fits to such models using the most updated LHC Higgs-boson data and discuss the corresponding implications on Higgs-portal-type models. In particular we find that the current LHC Higgs-boson data slightly favors the SM over the Higgs-portal singlet-scalar models, which has to be further examined using the upcoming LHC Higgsboson data. Finally, without non-SM particles contributing to the Hγγ and Hgg vertices, the Higgs-portal models are constrained as follows: cos α 0.86 and ∆Γ tot 1.24 MeV at 95% confidence level (CL).