Electroweak baryogenesis via bottom transport: complementarity between LHC and future lepton collider probes

TL;DR

This paper explores how future lepton colliders and the LHC can jointly probe electroweak baryogenesis mechanisms involving an additional bottom Yukawa coupling in a two Higgs doublet model, highlighting potential discovery channels.

Contribution

It demonstrates the complementarity of LHC and future lepton colliders in detecting signatures of electroweak baryogenesis through bottom quark interactions in a general two Higgs doublet model.

Findings

LHC can probe the bottom Yukawa coupling for certain scalar masses.

Future electron-positron colliders can uniquely test the coupling via specific processes.

A 1 TeV collider with high luminosity could discover resonant diHiggs production related to phase transition.

Abstract

We study the complementarity between the Large Hadron Collider (LHC) and future lepton colliders in probing electroweak baryogenesis induced by an additional bottom Yukawa coupling $\rho_{bb}$. The context is general two Higgs doublet model (g2HDM) where such additional bottom Yukawa coupling can account for the observed baryon asymmetry of the Universe if $\mbox{Im}(\rho_{bb}) \gtrsim 0.058$. We find that LHC would probe the nominal $\mbox{Im}(\rho_{bb})$ required for baryogenesis to some extent via $bg \to bA \to bZh$ process if $300~\mbox{GeV}\lesssim m_A \lesssim 450$ GeV, where $A$ is the CP-odd scalar in g2HDM. We show that future electron positron collider such as International Linear Collider with $500$ GeV and 1 TeV collision energies may offer unique probe for the nominal $\mbox{Im}(\rho_{bb})$ via $e^+ e^- \to Z^*\to A H$ process followed by $A,H \to b \bar b$ decays in four $b$-jets signature. For complementarity we also study the resonant diHiggs productions, which may give an insight into strong first-order electroweak phase transition, via $e^+ e^- \to Z^*\to A H \to A h h$ process in six $b$-jets signature. We find that 1 TeV collision energy with $\mathcal{O}(1)~\text{ab}^{-1}$ integrated luminosity could offer an ideal environment for the discovery.