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Register a new userElectroweak phase transition in an extension of the Standard Model with scalar color octet
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In an extension of the Standard Model with a scalar color octet, the possibility of the strongly first-order electroweak phase transition is studied, by examining the finite-temperature effective Higgs potential at the one-loop level. It is found that there are wide regions in the parameter space that allow the strongly first-order electroweak phase transition, where the Higgs boson mass is larger than the experimental lower bound of 115 GeV, and the masses of the scalar color octet is around 200 GeV. The parameter regions may be explored at the LHC with respect to the electroweak phase transition.
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New physics at the weak scale that can couple to quarks typically gives rise to unacceptably large flavor changing neutral currents. An attractive way to avoid this problem is to impose the principal of minimal flavor violation (MFV). Recently it was noted that in MFV only scalars with the same gauge quantum numbers as the standard model Higgs doublet or color octet scalars with the same weak quantum numbers as the Higgs doublet can couple to quarks. In this paper we compute the one-loop rate for production of a single color octet scalar through gluon fusion at the LHC, which can become greater than the tree level pair production rate for octet scalar masses around a TeV. We also calculate the precision electroweak constraint from Z decays to a b and anti-b quark; this constraint on color octet mass and Yukawa coupling affects the allowed range for single octet scalar production through gluon fusion.
We provide the C++ tool BSMPT for calculating the strength of the electroweak phase transition in extended Higgs sectors. This relies on the loop-corrected effective potential at finite temperature including daisy resummation of the bosonic masses. The program allows to compute the vacuum expectation value (VEV) $v$ of the potential as a function of the temperature, and in particular the critical VEV $v_c$ at the temperature $T_c$ where the phase transition takes place. In addition, the loop-corrected trilinear Higgs self-couplings are provided. We apply an on-shell renormalization scheme in the sense that the loop-corrected masses and mixing angles are required to be equal to their tree-level input values. This allows for efficient scans in the parameter space of the models. The models implemented so far are the CP-conserving and the CP-violating 2-Higgs-Doublet Models (2HDM) and the Next-to-Minimal 2HDM (N2HDM). The program structure is such that the user can easily implement further models. Our tool can be used for the investigation of electroweak baryogenesis in models with extended Higgs sectors and the related Higgs self-couplings. The combination with parameter scans in the respective models allows to study the impact on collider phenomenology and to make a link between collider phenomenology and cosmology. The program package can be downloaded at: https://github.com/phbasler/BSMPT.
We consider a non-Abelian dark SU(2)$_{rm D}$ model where the dark sector couples to the Standard Model (SM) through a Higgs portal. We investigate two different scenarios of the dark sector scalars with $Z_2$ symmetry, with Higgs portal interactions that can introduce mixing between the SM Higgs boson and the SM singlet scalars in the dark sector. We utilize the existing collider results of the Higgs signal rate, direct heavy Higgs searches, and electroweak precision observables to constrain the model parameters. The $text{SU(2)}_{text{D}}$ partially breaks into $text{U(1)}_{text{D}}$ gauge group by the scalar sector. The resulting two stable massive dark gauge bosons and pseudo-Goldstone bosons can be viable cold dark matter candidates, while the massless gauge boson from the unbroken $text{U(1)}_{text{D}}$ subgroup is a dark radiation and can introduce long-range attractive dark matter (DM) self-interaction, which can alleviate the small-scale structure issues. We study in detail the pattern of strong first-order phase transition and gravitational wave (GW) production triggered by the dark sector symmetry breaking, and further evaluate the signal-to-noise ratio for several proposed space interferometer missions. We conclude that the rich physics in the dark sector may be observable with the current and future measurements at colliders, DM experiments, and GW interferometers.
The Higgs potential of the minimal nonminimal supersymmetric standard model (MNMSSM) is investigated within the context of electroweak phase transition. We investigate the allowed parameter space yielding correct electroweak phase transitoin employing a high temperature approximation. We devote to phenomenological consequences for the Higgs sector of the MNMSSM for electron-positron colliders. It is observed that a future $e^+ e^-$ linear collider with $sqrt{s} = 1000$ GeV will be able to test the model with regard to electroweak baryogenesis.
In this work we study the collider phenomenology of color-octet scalars (sgluons) in minimal supersymmetric models endowed with a global continuous $R$ symmetry. We systematically catalog the significant decay channels of scalar and pseudoscalar sgluons and identify novel features that are natural in these models. These include decays in nonstandard diboson channels, such as to a gluon and a photon; three-body decays with considerable branching fractions; and long-lived particles with displaced vertex signatures. We also discuss the single and pair production of these particles and show that they can evade existing constraints from the Large Hadron Collider, to varying extents, in large regions of reasonable parameter space. We find, for instance, that a 725 GeV scalar and a 350 GeV or lighter pseudoscalar can still be accommodated in realistic scenarios.
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