Speaker
Description
In this talk we investigate the capability of the new ATLAS searches for
$A \to ZH$ decays in $ell^+ \ell^- t \bar t$ and $\nu \nu b \bar b$
final states to probe the electroweak phase transition in the early
Universe. In the framework of the Two Higgs Doublet Model (2HDM), we
investigate the impact of the new searches on the 2HDM parameter space,
paying special attention to parameter space regions that predict a
strong first order electroweak phase transition. We discuss the
complementarity with other LHC searches, and we analyze the interplay of
collider searches and space based gravitational wave experiments. We
furthermore show that the $3\sigma$ excess observed at $m_A = 650$~GeV
and $m_H = 450$~GeV can be described in the 2HDM, where the preferred
parameter space falls within the region suitable for a realization of a
strong first-order phase transition. The GW signal produced during the
transition in the early universe might be in reach of LISA. Finally, we
present a python package for the exploration of the 2HDM parameter space
that can be used to confront the model with the most significant
theoretical and experimental constraints.
