CP violation in the extension of SM with a complex singlet scalar and vector quarks

TL;DR

This paper explores a model extending the Standard Model with a complex singlet and vector quarks, demonstrating spontaneous CP violation, baryon asymmetry explanation, and analyzing experimental constraints on heavy quark production and Higgs signals.

Contribution

It introduces a novel extension of the SM with spontaneous CP violation via a complex singlet and vector quarks, and studies its phenomenological implications.

Findings

The model can account for the observed baryon-to-entropy ratio.

Constraints on heavy quark masses from collider data are established.

Heavy quarks influence Higgs signal strength and gauge boson propagators.

Abstract

We consider the simplest extension of the SM with a complex singlet and a pair of heavy doublet vector quarks, the so-called cSMCS model. In this model, the CP violation can emerge spontaneously as a consequence of the time-dependent phase of the complex singlet vacuum expectation value and the mass mixing of the SM and heavy vector quarks. In our model, the CP-violating time-dependent phase depends on the Higgs field within the bubble-wall via the Higgs-singlet coupling that can directly explain the observed baryon-to-entropy ratio $\sim 9\times 10^{-11}$. Additionally, as a result of the mixing between vector quarks and SM quarks, the tree level Flavour Changing Neutral Currents and the charged-current decay channels $t' \to Wb, \, Zt, \, h_{i} t$ and $b' \to Wt, \, Zb, \, h_{i} b$ would arise that are well constrained by experimental data. We investigate the implications of these constraints on the total cross-section for the production of heavy vector quark pairs via $pp \to t'\bar{t'}$ and $pp \to b'\bar{b'}$ channels and obtain the bounds on the heavy quark masses for this model. Accordingly, we show the contribution of these heavy quarks in the Higgs bosons signal strength, $\mathcal{R}_{\gamma\gamma}$, as well as corrections to the gauge boson propagators.