CP violation in the secluded U(1)'-extended MSSM

TL;DR

This paper explores CP violation in the Higgs sector of the secluded U(1)'-extended MSSM, analyzing how complex phases affect Higgs masses and couplings under various constraints, and identifying conditions for spontaneous CP violation.

Contribution

It provides a detailed analysis of CP violation effects in the sMSSM Higgs sector, including the impact of complex soft SUSY breaking masses and the potential for spontaneous CP violation.

Findings

Allowed electroweak vacuum region is limited by model parameters.

Lightest Higgs can be lighter than Z boson with suppressed Z coupling.

Maximal Higgs mass can exceed 100 GeV with CP violation.

Abstract

We study the Higgs sector of the secluded $U(1)'$-extended MSSM (sMSSM) focusing on CP violation. Using the one-loop effective potential that includes contributions from quarks and squarks in the third generation, we search for the allowed region under theoretical and experimental constraints. It is found that the possible region for the electroweak vacuum to exist is quite limited, depending on the parameters in the model. The masses and couplings of the Higgs bosons are calculated with/without CP violation. Even at the tree level, CP violation is possible by complex soft SUSY breaking masses. Similar to the CPX scenario in the MSSM, the scalar-pseudoscalar mixing enables the lightest Higgs boson mass to become smaller than the $Z$ boson mass while the coupling with the $Z$ boson is sufficiently suppressed to avoid the LEP experimental constraints. However, unlike the CPX scenario, large $\mu$ and $A$ are not required for the realization of large CP violation. The typical spectrum of the SUSY particles is thus different. We also investigate the possible upper bound of the lightest Higgs boson in the case of spontaneous CP violation. The maximal value of it can reach above 100 GeV with maximal CP-violating phases.