Least fine-tuned U(1) extended SSM

Abstract

We consider the Higgs boson mass in a class of the UMSSM models in which the MSSM gauge group is extended by an additional U (1) group. Implementing the universal boundary condition at the GUT scale we target phenomenologically interesting regions of UMSSM where the necessary radiative contributions to the lightest CP-even Higgs boson mass are significantly small and LSP is always the lightest neutralino. We find that the smallest amount of radiative contributions to the Higgs boson mass is about 50 GeV in UMSSM, this result is much lower than that obtained in the MSSM framework, which is around 90 GeV. Additionally, we examine the Higgs boson properties in these models in order to check whether if it can behave similar to the SM Higgs boson under the current experimental constraints. We find that enforcement of smaller radiative contribution mostly restricts the U (1) breaking scale as v S 10 TeV. Besides, such low contributions demand h S ∼ 0.2 − 0.45. Because of the model dependency in realizing these radiative contributions θ E 6 < 0 are more favored, if one seeks for the solutions consistent with the current dark matter constraints. As to the mass spectrum, we find that stop and stau can be degenerate with the LSP neutralino in the range from 300 GeV to 700 GeV; however, the dark matter constraints restrict this scale as mt, mτ 500 GeV. Such degenerate solutions also predict stop-neutralino and stau-neutralino coannihilation channels, which are effective to reduce the relic abundance of neutralino down to the ranges consistent with the current dark matter observations. Finally, we discuss the effects of heavy M Z in the fine-tuning. Even though the radiative contributions are significantly low, the required fine-tuning can still be large. We comment about reinterpretation of the fine-tuning measure in the UMSSM framework, which can yield efficiently low results for the fine-tuning the electroweak scale.1

Charged Higgs boson in MSSM and beyond

“…On the other hand, this bound can vary model dependently, and a most recent study [47] has shown that M Z 0 ≳ 2.5 TeV can survive, if Z 0 is leptophobic. Based on our previous study [19], which was conducted in the similar parameter space, the leptonic decay processes of Z 0 are found as BRðZ 0 → llÞ ≲ 14%. Since the leptonic decays of Z 0 are found rather low, we set the mass bound on Z 0 as M Z 0 ≥ 2.5 TeV.…”

“…However, as shown in a recent study [19], Z 0 may barely decay into two leptons; hence such strict bounds can be relaxed. Moreover, its neutral superpartner (B 0 ) is also included in the low energy spectrum as required by SUSY.…”

“…(18) reflects the contribution from the Uð1Þ 0 sector, where g Y 0 is the gauge coupling associated with Uð1Þ 0 , Q H u and Q H d are the charges of H u and H d under the Uð1Þ 0 group. After these contributions, the tree-level Higgs boson mass can be obtained as large as about 140 GeV for low tan β, while it can be as heavy as about 115 GeV, when tan β is large [19]. Similarly, other Higgs bosons receive contributions from the Uð1Þ 0 sector, and the charged Higgs boson mass can be obtained at tree level as…”

“…The recent studies have shown that new flavor states, which are allowed to mix with the MSSM neutralinos, can significantly alter the DM implications [21]. The fundamental parameter space for NMSSM and UMSSM is restricted based on our previous studies [19,56], which explored the regions with acceptable fine-tuning in the fundamental parameter space of UMSSM.…”

Stop search in SUSY SO(10) GUTs with nonuniversal Gaugino masses

“…(8), which results in independent non-universal SSB mass terms for the gauginos. Despite a variety of different breaking patterns of SO(10) symmetry which may yield different extensions of MSSM, most of them lead to similar implications when one considers the masses, decay channels and possible signals for the stop and gluino [143][144][145][146]. Even though they can yield LSPs other than MSSM neutralinos [147][148][149][150][151], stop and gluino either do not directly decay into such LSPs [152] or they do interact very weakly [153].…”