Same-sign dilepton excesses and vector-like quarks

Chen, Chuan-Ren; Cheng, H. J.; Low, Ian

doi:10.1007/jhep03(2016)098

Cited by 6 publications

(8 citation statements)

References 56 publications

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“…We will show that an additional contribution arising from the production of the Z in association with top quarks (ttZ ) could provide an explanation for the observed excess. (For previous theoretical studies of this excess, see [11][12][13][14][15].) We stress that a more precise measurement of this Higgs production mechanism will be one of the key objectives at the LHC Run II, making our study relevant for the near future.…”

Section: Jhep06(2016)110mentioning

confidence: 99%

Novel collider and dark matter phenomenology of a top-philic Z ′

Cox

Medina

Ray

et al. 2016

J. High Energ. Phys.

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We consider extending the Standard Model by including an additional Abelian gauge group broken at low energies under which the right-handed top quark is the only effectively charged Standard Model fermion. The associated gauge boson (Z ) is then naturally top-philic and couples only to the rest of the SM particle content at loop-level or via kinetic mixing with the hypercharge gauge boson which is assumed to be small. Working at the effective theory level, we demonstrate that such a minimal extension allows for an improved fitting of the ∼ 2σ excess observed in tth searches at the LHC in a region of parameter space that satisfies existing collider constraints. We also present the reach of the LHC at 13 TeV in constraining the relevant region of parameter space. Additionally we show that within the same framework a suitably chosen fermion charged only under the exotic Abelian group can, in the region of parameter space preferred by thetth measurements, simultaneously explain the dark matter relic density and the γ-ray excess at the galactic center observed by the Fermi-LAT experiment.

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Section: Jhep06(2016)110mentioning

confidence: 99%

Novel collider and dark matter phenomenology of a top-philic Z ′

Cox

Medina

Ray

et al. 2016

J. High Energ. Phys.

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“…The tth production excess is mainly driven by the multi-lepton channel and is one of several excesses in searches in final states consisting of bottom quarks and many leptons [16][17][18]. Such excesses were also explained in models with standard Higgs sector by introducing new scalar or fermion particles [19][20][21].…”

Section: Jhep02(2017)050mentioning

confidence: 99%

Enhanced Higgs associated production with a top quark pair in the NMSSM with light singlets

Badziak

Wagner

2017

J. High Energ. Phys.

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Precision measurements of the 125 GeV Higgs resonance recently discovered at the LHC have determined that its properties are similar to the ones of the Standard Model (SM) Higgs boson. However, the current uncertainties in the determination of the Higgs boson couplings leave room for significant deviations from the SM expectations. In fact, if one assumes no correlation between the top-quark and gluon couplings to the Higgs, the current global fit to the Higgs data lead to central values of the Higgs couplings to the bottom-quark and the top-quark that are about 2 σ away from the SM predictions. In a previous work, we showed that such a scenario could be realized in the Next to Minimal Supersymmetric extension of the SM (NMSSM), for heavy singlets and light MSSM-like Higgs bosons and scalar top quarks, but for couplings that ruined the perturbative consistency of the theory up to the GUT scale. In this work we show that a perturbative consistent scenario, for somewhat heavier stops, may be obtained in the presence of light singlets. An interesting bonus of this scenario is the possibility of explaining an excess of events observed in CP-even Higgs searches at LEP2.

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“…For the electroweak singlet T , no dedicated searches exist, although there exist searches for the scalar top quark (stop) in supersymmetry which also decays to tt + MET. These limits, 4 The T field can also have a coupling with S as y ST iγ 5 T , which slightly increases the diphoton rate. 5 The λ term in Eq.…”

Section: Vector-like Quarks and Multilepton Excessmentioning

confidence: 99%

“…As was pointed out in Refs. [3,4], the multilepton excesses were observed with varying degrees of significance in many Run 1 analyses in both ATLAS and CMS collaborations, which include searches for ttH production [5,6], for scalar bottom quarks in supersymmetry [7,8], for SM production of ttW [9, 10] and for heavy VLQs [11]. (The CMS Run 1 search for VLQ's, which imposes very hard cuts on the kinematics, is the only exception which didn't see an excess [12].)…”

Section: Introductionmentioning

confidence: 99%

“…In the Monte Carlo simulation we generate signal events using Madgraph [146] + Pythia [147] + Delphes[148] and a tagging efficiency of b-jet at 77%. In the ttH channel we implement the same cuts as in Ref [4]. at both 8 TeV and 13 TeV, and normalize the resulting events to the number expected from the Such a decay could arise from the interaction Sφφ, which is irrelevant for our study for m φ ≥ m S /2.…”

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confidence: 99%

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From the 750 GeV diphoton resonance to multilepton excesses

et al. 2016

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Weakly-coupled models for the 750 GeV diphoton resonance often invoke new particles carrying both color and/or electric charges to mediate loop-induced couplings of the resonance to two gluons and two photons. The new colored particles may not be stable and could decay into final states containing standard model particles. We consider an electroweak doublet of vector-like quarks (VLQs) carrying electric charges of 5/3 and 2/3, respectively, which mediate the loop-induced couplings of the 750 GeV resonance. If the VLQ has a mass at around 1 TeV, it naturally gives rise to the observed diphoton signal strength while all couplings remain perturbative up to a high scale. At the same time, if the charge-5/3 VLQ decays into final states containing top quark and W boson, it would contribute to the multilepton excesses observed in both Run 1 and Run 2 data.It is also possible to incorporate a dark matter candidate in the decay final states to explain the observed relic density.

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Same-sign dilepton excesses and vector-like quarks

Cited by 6 publications

References 56 publications

Novel collider and dark matter phenomenology of a top-philic Z ′

Novel collider and dark matter phenomenology of a top-philic Z ′

Enhanced Higgs associated production with a top quark pair in the NMSSM with light singlets

From the 750 GeV diphoton resonance to multilepton excesses

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