Theoretical constraints on new generations with and without quarks or neutrinos

Knochel, Alexander; Wetterich, C.

doi:10.1016/j.physletb.2011.09.004

Cited by 6 publications

(5 citation statements)

References 19 publications

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“…As yet another model building alternative, instead of single lepton doublet with hypercharge Y (L L ) = −3/2, one can saturate the Witten anomaly by introducing three SM-like lepton doublets, and a stable heavy neutrino among these three becomes a plausible dark matter candidate. Various further possibilities of nonsequential generations beyond the SM have been considered in literature [24,25].…”

Section: Model Lagrangian and Mass Termsmentioning

confidence: 99%

Invisible Higgs and dark matter

Heikinheimo

Tuominen

Virkajärvi

2012

J. High Energ. Phys.

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Abstract:We investigate the possibility that a massive weakly interacting fermion simultaneously provides for a dominant component of the dark matter relic density and an invisible decay width of the Higgs boson at the LHC. As a concrete model realizing such dynamics we consider the minimal walking technicolor, although our results apply more generally. Taking into account the constraints from the electroweak precision measurements and current direct searches for dark matter particles, we find that such scenario is heavily constrained, and large portions of the parameter space are excluded.

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Section: Model Lagrangian and Mass Termsmentioning

confidence: 99%

Invisible Higgs and dark matter

Heikinheimo

Tuominen

Virkajärvi

2012

J. High Energ. Phys.

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“…Large masses of the fourth-generation fermions lead to nonperturbativity of Yukawa couplings at a low scale Λ M GU T as well as instability of the vacuum. This has been investigated in the context of models without supersymmetry (SUSY) [41,67,[69][70][71][72] and with SUSY [73], after taking into account various bounds from precision EW data as well as collider and direct search experiments on sequential heavy fermions.…”

Section: Introductionmentioning

confidence: 99%

Large mass splittings for fourth generation fermions allowed by LHC Higgs boson exclusion

Dighe¹,

Ghosh²,

Godbole³

et al. 2012

Phys. Rev. D

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In the context of the standard model with a fourth generation, we explore the allowed mass spectra in the fourth-generation quark and lepton sectors as functions of the Higgs mass. Using the constraints from unitarity and oblique parameters, we show that a heavy Higgs allows large mass splittings in these sectors, opening up new decay channels involving W emission. Assuming that the hints for a light Higgs do not yet constitute an evidence, we work in a scenario where a heavy Higgs is viable. A Higgs heavier than ∼ 800 GeV would in fact necessitate either a heavy quark decay channel t → b W/b → t W or a heavy lepton decay channel τ → ν W as long as the mixing between the third and fourth generations is small. This mixing tends to suppress the mass splittings and hence the W -emission channels. The possibility of the W -emission channel could substantially change the search strategies of fourth-generation fermions at the LHC and impact the currently reported mass limits.

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“…Simultaneously satisfying these four conditions strongly restricts the combinations of representations which are allowed and only the following (minimal) spectra, given in terms of left-handed spinors, satisfy these requirements [44,45] I : (3, 2) 1/6 ⊕ (3, 1) −2/3 ⊕ (3, 1) 1/3 ⊕ (1, 2) −1/2 ⊕ (1, 1) 1…”

Section: Motivating Guts Without Weak Scale Susymentioning

confidence: 99%

Precision unification and proton decay in F-theory GUTs with high scale supersymmetry

Hebecker¹,

Unwin

2014

J. High Energ. Phys.

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F-theory GUTs provide a promising UV completion for models with approximate gauge coupling unification, such as the (non-supersymmetric) Standard Model. More specifically, if the superparters have masses well above the TeV scale, the resulting imperfection in unification can be accounted for by the, in principle calculable, classical F-theory correction at the high scale. In this paper we argue for the correct form of the F-theory corrections to unification, including KK mode loop effects. However, the price of compensating the imprecise unification in such High Scale SUSY models with F-theory corrections is that the GUT scale is lowered, potentially leading to a dangerously high proton decay rate from dimension-6 operators. We analyse the possibility of suppressing the decay rate by the localization of X, Y gauge bosons in higher dimensions. While this effect can be very strong for the zero modes, we find that in the simplest models of this type it is difficult to realize a significant suppression for higher modes (Landau levels). Notably, in the absence of substantial suppressions to the proton decay rate, the superpartners must be lighter than 100 TeV to satisfy proton decay constraints. We highlight that multiple correlated signals of proton decay could verify this scenario.

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Theoretical constraints on new generations with and without quarks or neutrinos

Cited by 6 publications

References 19 publications

Invisible Higgs and dark matter

Invisible Higgs and dark matter

Large mass splittings for fourth generation fermions allowed by LHC Higgs boson exclusion

Precision unification and proton decay in F-theory GUTs with high scale supersymmetry

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