Stabilizing the Higgs potential with a Z′ (original) (raw)
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Electroweak couplings and LHC constraints on alternative Z′ models in E6
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We report the most general expression for the chiral charges of a [Formula: see text] gauge boson coming from an [Formula: see text] unification model, as a function of the electroweak parameters and the charges of the [Formula: see text] factors in the chain of subgroups. These charges are valid for an arbitrary Higgs sector and only depend on the branching rules of the [Formula: see text] fundamental representation and the corresponding rules for the fermionic representations of their subgroups. By assuming [Formula: see text] unification, the renormalization group equations (RGE) allow us to calculate the electroweak parameters at low energies for most of the chains of subgroups in [Formula: see text]. From RGE and unitary conditions, we show that at low energies there must be a mixing between the gauge boson of the standard model hypercharge and the [Formula: see text]. From this, it is possible to delimit the preferred region in the parameter space for a breaking pattern in [Fo...
Physical Review D, 2014
We study the standard model (SM) in its full perturbative validity range between ΛQCD and the U (1)Y Landau pole, assuming that a yet unknown gravitational theory in the UV does not introduce additional particle thresholds, as suggested by the tiny cosmological constant and the absence of new stabilising physics at the EW scale. We find that, due to dimensional transmutation, the SM Higgs potential has a global minimum at 10 26 GeV, invalidating the SM as a phenomenologically acceptable model in this energy range. We show that extending the classically scale invariant SM with one complex singlet scalar S allows us to: (i) stabilise the SM Higgs potential; (ii) induce a scale in the singlet sector via dimensional transmutation that generates the negative SM Higgs mass term via the Higgs portal; (iii) provide a stable CP-odd singlet as the thermal relic dark matter due to CP-conservation of the scalar potential; (iv) provide a degree of freedom that can act as an inflaton in the form of the CP-even singlet. The logarithmic behaviour of dimensional transmutation allows one to accommodate the large hierarchy between the electroweak scale and the Landau pole, while understanding the latter requires a new non-perturbative view on the SM.
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We explore the electroweak vacuum stability in the framework of a recently proposed paradigm for the origin of Yukawa couplings. These arise as low energy effective couplings radiatively generated by portal interactions with a hidden, or dark, sector at the one-loop level. Possible tree-level Yukawa couplings are forbidden by a new underlying symmetry, assumed to be spontaneously broken by the vacuum expectation value of a new scalar field above the electroweak scale. As a consequence, the top Yukawa interaction ceases to behave as a local operator at energies above the new sector scale and, therefore, cannot contribute to the running of the quartic Higgs coupling at higher energies. By studying two complementary scenarios, we explicitly show that the framework can achieve the stability of the electroweak vacuum without particular tuning of parameters. The proposed mechanism requires the existence of a dark sector and new portal messenger scalar interactions that, connecting the Sta...