Speaker
Description
We perform a comprehensive scan of the parameter space of a general singlet scalar
extension of the Standard Model to identify the regions which can lead to a strong first-
order phase transition, as required by the electroweak baryogenesis mechanism. We find
that taking into account bubble nucleation is a fundamental constraint on the parameter
space and present a conservative and fast estimate for it so as to enable efficient param-
eter space scanning. The allowed regions turn out to be already significantly probed by
constraints on the scalar mixing from Higgs signal strength measurements. We also con-
sider the addition of new neutrino singlet fields with Yukawa couplings to both scalars
and forming heavy (pseudo)-Dirac pairs, as in the linear or inverse Seesaw mechanisms
for neutrino mass generation. We find that their inclusion does not alter the allowed pa-
rameter space from early universe phenomenology in a significant way. Conversely, there
are allowed regions of the parameter space where the presence of the neutrino singlets
would remarkably modify the collider phenomenology, yielding interesting new signatures
in Higgs and singlet scalar decays.
