Electroweak Phase Transition, Higgs Diphoton Rate, and New Heavy Fermions

Abstract

We show that weak scale vector-like fermions with order one couplings to the Higgs can lead to a novel mechanism for a strongly first-order electroweak phase transition (EWPhT), through their tendency to drive the Higgs quartic coupling negative. These same fermions could also enhance the loop-induced branching fraction of the Higgs into two photons, as suggested by the recent discovery of a ~125 GeV Higgs-like state at the CERN Large Hadron Collider (LHC). Our results suggest that measurements of the diphoton decay rate of the Higgs and its self coupling, at the LHC or perhaps at a future lepton collider, could probe the EWPhT in the early Universe, with significant implications for the viability of electroweak baryogenesis scenarios.

6 pages, 1 figure. Revised version shows that the original conclusions hold in a distinct region of parameter space. New discussion on collider probes added

References in corpus (5)

• Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC
• Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC
• Dynamics of Non-renormalizable Electroweak Symmetry Breaking
• Higgs Self-Coupling as a Probe of Electroweak Phase Transition
• On the Higgs Fit and Electroweak Phase Transition

Cited by in corpus (32)

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• Diphoton Decay Excess and 125 GeV Higgs Boson in Gauge-Higgs Unification
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• $SU(2)\otimes SU(2)$ Gauge Extensions of the MSSM Revisited
• Electroweak Baryogenesis with Vector-like Leptons and Scalar Singlets
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