Electroweak phase transition confronted with dark matter detection constraints

TL;DR

This paper investigates the interplay between electroweak phase transitions and dark matter constraints in singlet scalar extensions of the Standard Model, identifying viable parameter spaces for future experimental tests.

Contribution

It provides a comprehensive analysis of real and complex singlet models, highlighting the conditions under which a strong electroweak phase transition and viable dark matter relic density coexist.

Findings

Real singlet models face strong direct detection constraints, limiting dark matter fraction.

Complex singlet models can accommodate both phase transition and dark matter relic density.

Future experiments like HL-LHC and XENONnT can probe the identified parameter space.

Abstract

We study the type-II first-order electroweak phase transition and dark matter (DM) phenomenology in both real and complex singlet extensions of SM. In the real singlet extension with a $\mathbb{Z}_2$ symmetry, we show that the parameter regions favored by the phase transition suffer from strong constraints from DM direct detection so that only a negligible fraction ($f_{X}\sim 10^{-4}-10^{-5}$) of DM composed of the real singlet scalar can survive the LUX and XENON1T constraints. In the complex singlet $S$ case, we impose a $CP$ symmetry $S\to S^{*}$ to the scalar potential. The real component of $S$ can mix with SM Higgs boson while the imaginary component becomes a DM candidate due to the protection of the $CP$ symmetry. By taking into account the current experimental constraints of invisible Higgs decays, Higgs signal strength measurements, and dark matter detections, we find that there exists a large parameter space for the type-II electroweak phase transition to occur while explaining all of the dark matter relic density. We identify a subset of parameter space that is promising for future experiments, including the di-Higgs and Higgs signal strength measurements at the HL-LHC and the dark matter direct detection in the XENONnT project.