More Higgses at the LHC and the Electroweak Phase Transition

A cosmological first order electroweak phase transition could explain the origin of the cosmic matter-antimatter asymmetry. While it does not occur in the Standard Model, it becomes possible in the presence of a second Higgs doublet. In this context, we obtain the properties of the new scalars $H_0$, $A_0$ and $H^{\pm }$ leading to such a phase transition, showing that its key LHC signature would be the decay $A_0\to H_{0}Z$, and we analyze the promising LHC search prospects for this decay in the $\mathrm{\ell }\mathrm{\ell }b\bar{b}$ and $\mathrm{\ell }\mathrm{\ell }{W}^{+}{W}^{-}$ final states. Finally, we comment on the impact of the $A_0\to H_{0}Z$ decay on current LHC searches for $A_0$ decaying into SM particles.