750 GeV Di-photon Excess and Strongly First-Order Electroweak Phase Transition

TL;DR

This paper proposes a model explaining the 750 GeV diphoton excess with a new scalar, which also allows for a strongly first-order electroweak phase transition, potentially enabling electroweak baryogenesis and making testable predictions for future experiments.

Contribution

It introduces a scalar particle model that explains the diphoton excess and simultaneously supports a strongly first-order electroweak phase transition, linking collider signals to baryogenesis.

Findings

Predicted di-Higgs production cross section ≥ 20 fb at 13 TeV LHC

Higgs cubic self-coupling enhanced by ≥ 40% over SM

Model contains a large viable parameter space for strong EWPT

Abstract

A new scalar particle, coupled to photons and gluons via loops of vector-like quarks, provides a simple theoretical interpretation of the 750 GeV diphoton excess reported by the experiments at the Large Hadron Collider (LHC). In this paper, we show that this model contains a large, phenomenologically viable parameter space region in which the electroweak phase transition (EWPT) is strongly first-order, opening the possibility that electroweak baryogenesis mechanism can be realized in this context. A large coupling between the Higgs doublet and the heavy scalar, required for a strongly first-order EWPT, can arise naturally in composite Higgs models. The scenario makes robust predictions that will be tested in near-future experiments. The cross section of resonant di-Higgs production at the 13 TeV LHC is predicted to be at least 20 fb, while the Higgs cubic self-coupling is enhanced by 40% or more with respect to its Standard Model (SM) value.