Top-assisted di-Higgs boson production motivated by baryogenesis

Abstract

We study top-assisted di-Higgs production via $cg\ensuremath{\rightarrow}tH\ensuremath{\rightarrow}thh$, where $h$ is the 125 GeV scalar boson and $H$ is the $CP$-even heavy Higgs. The context is the two Higgs doublet model without a ${Z}_{2}$ symmetry, where the extra Yukawa coupling ${\ensuremath{\rho}}_{tc}$ generates $tH$ production, with the extra top Yukawa ${\ensuremath{\rho}}_{tt}\ensuremath{\simeq}0$ to avoid $gg\ensuremath{\rightarrow}H$ constraints. We find that discovery is possible for ${m}_{H}$ around 300 GeV or so at the LHC but would need finite $h\ensuremath{-}H$ mixing angle $\mathrm{cos}\ensuremath{\gamma}$ to allow for finite ${\ensuremath{\lambda}}_{Hhh}$ coupling, and ${\ensuremath{\rho}}_{tc}$ also needs to be not too small. A sizable ${\ensuremath{\rho}}_{tc}$ could drive electroweak baryogenesis, which further motivates the search.