Lepton-mediated electroweak baryogenesis, gravitational waves and the $4\tau$ final state at the collider

TL;DR

This paper proposes a leptophilic extension of the Standard Model to achieve electroweak baryogenesis, predicts detectable gravitational waves, and suggests collider signatures involving four tau leptons, with future experiments capable of testing the model.

Contribution

It introduces a novel leptophilic model with a singlet scalar and dimension-5 operators for electroweak baryogenesis, linking it to gravitational wave signals and collider phenomenology.

Findings

The model successfully generates the observed baryon asymmetry.

Gravitational wave signals from the phase transition are detectable by future space-based detectors.

Collider signatures involving four tau leptons can be observed at HL-LHC and HE-LHC.

Abstract

An electroweak baryogenesis (EWBG) mechanism mediated by $\tau$ lepton transport is proposed. We extend the Standard Model with a real singlet scalar $S$ to trigger the strong first-order electroweak phase transition (SFOEWPT), and with a set of leptophilic dimension-5 operators to provide sufficient CP violating source. We demonstrate this model is able to generate the observed baryon asymmetry of the universe. This scenario is experimentally testable via either the SFOEWPT gravitational wave signals at the next-generation space-based detectors, or the $pp\to h^*\to SS\to 4\tau$ process (where $h^*$ is an off-shell Higgs) at the hadron colliders. A detailed collider simulation shows that a considerable fraction of parameter space can be probed at the HL-LHC, while almost the whole parameter space allowed by EWBG can be reached by the 27 TeV HE-LHC.