LHC Signatures of Vector-Like Quarks

Okada, Yasuhiro; Panizzi, Luca

doi:10.1155/2013/364936

Cited by 91 publications

(71 citation statements)

References 143 publications

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“…The minimal set of VL multiplets that can mix with SM quarks and a SM (or SM-like) Higgs boson have been extensively studied in literature [23,28,32,[34][35][36]40].…”

Section: Vector-like Multipletsmentioning

confidence: 99%

“…Initially, simplifying assumptions were considered (mixing only with the third generation of SM quark family or specific decay modes) [23][24][25][26][27][28][29][30][31][32][33]. However the most recent analyses, due to larger data samples, allow exploring more general situations with mixing of VL quarks with the first two generation of SM quarks [34][35][36][37][38]. There are some works analyzing the phenomenology of exotic quarks [39].…”

Section: Introductionmentioning

confidence: 99%

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Interplay of vector-like top partner multiplets in a realistic mixing set-up

Cacciapaglia

Deandrea

Gaur

et al. 2015

J. High Energ. Phys.

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The ATLAS and CMS collaborations at the LHC have performed analyses on the existing data sets, studying the case of one vector-like fermion or multiplet coupling to the standard model Yukawa sector. In the near future, with more data available, these experimental collaborations will start to investigate more realistic cases. The presence of more than one extra vector-like multiplet is indeed a common situation in many extensions of the standard model. The interplay of these vector-like multiplet between precision electroweak bounds, flavour and collider phenomenology is a important question in view of establishing bounds or for the discovery of physics beyond the standard model. In this work we study the phenomenological consequences of the presence of two vector-like multiplets. We analyse the constraints on such scenarios from tree-level data and oblique corrections for the case of mixing to each of the SM generations. In the present work, we limit to scenarios with two top-like partners and no mixing in the down-sector.

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“…The minimal set of VL multiplets that can mix with SM quarks and a SM (or SM-like) Higgs boson have been extensively studied in literature [23,28,32,[34][35][36]40].…”

Section: Vector-like Multipletsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Interplay of vector-like top partner multiplets in a realistic mixing set-up

Cacciapaglia

Deandrea

Gaur

et al. 2015

J. High Energ. Phys.

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“…Vector-like quarks may exist as isospin singlets, doublets, or triplets. Arguments based on naturalness suggest that VLQ may not interact strongly with light SM quarks [23,24]. Thus it is assumed for this analysis that VLQ decay predominantly to third-generation SM quarks.…”

Section: Introductionmentioning

confidence: 99%

Analysis of events with b-jets and a pair of leptons of the same charge in pp collisions at s = 8 $$ \sqrt{s}=8 $$ TeV with the ATLAS detector

Aad¹,

Abbott²,

Abdallah³

et al. 2015

J. High Energ. Phys.

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Analysis of events with b-jets and a pair of leptons of the same charge in pp collisions at √ s = 8 TeV with the ATLAS detectorThe ATLAS collaboration E-mail: atlas.publications@cern.chAbstract: An analysis is presented of events containing jets including at least one btagged jet, sizeable missing transverse momentum, and at least two leptons including a pair of the same electric charge, with the scalar sum of the jet and lepton transverse momenta being large. A data sample with an integrated luminosity of 20.3 fb −1 of pp collisions at √ s = 8 TeV recorded by the ATLAS detector at the Large Hadron Collider is used. Standard Model processes rarely produce these final states, but there are several models of physics beyond the Standard Model that predict an enhanced rate of production of such events; the ones considered here are production of vector-like quarks, enhanced fourtop-quark production, pair production of chiral b -quarks, and production of two positively charged top quarks. Eleven signal regions are defined; subsets of these regions are combined when searching for each class of models. In the three signal regions primarily sensitive to positively charged top quark pair production, the data yield is consistent with the background expectation. There are more data events than expected from background in the set of eight signal regions defined for searching for vector-like quarks and chiral b -quarks, but the significance of the discrepancy is less than two standard deviations. The discrepancy reaches 2.5 standard deviations in the set of five signal regions defined for searching for four-top-quark production. The results are used to set 95% CL limits on various models. The ATLAS collaboration 35 IntroductionThe Standard Model (SM) has been repeatedly confirmed experimentally. Nonetheless there is a need for physics beyond the SM (BSM) at about the TeV scale, with additional features that explain the baryon asymmetry of the universe, specify the nature of dark matter, and provide a mechanism to naturally stabilize the Higgs boson mass at its observed value of approximately 125 GeV [1,2]. This paper reports on a search for BSM physics resulting in pairs of isolated high-transverse-momentum (high-p T ) leptons 1 with the same electric charge, hereafter denoted as same-sign leptons, (or three or more leptons of any charge) missing transverse momentum, and b-jets. This is a promising search channel since the SM yields of such events are small, and several types of BSM physics may contribute. Among the models that predict enhanced same-sign lepton production are those that postulate the existence of vector-like quarks, an enhancement of the four-top-quark production cross section, the existence of a fourth generation of chiral quarks, or production of two positively charged top quarks. A common data sample is used to search for each of 1 Only electrons and muons are considered in the search. Tau leptons are not explicitly reconstructed, but electrons and muons from τ decay may enter the selected samples. Table ...

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“…we find no competitive bound for m X3 (so its lower value is then fixed to 500 GeV [76]), for m X6 833 GeV and for m X10,X15 4000 GeV. The latter, being at the LHC kinematical threshold, is therefore expected to be somewhat degraded.…”

Section: A Production Cross-section and Vl Fermion Mass Limitsmentioning

confidence: 71%

Diboson anomaly: Heavy Higgs resonance and QCD vectorlike exotics

et al. 2016

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The ATLAS collaboration (and also CMS) has recently reported an excess over Standard Model expectations for gauge boson pair production in the invariant mass region 1.8 − 2.2 TeV. In the light of these results, we argue that such signal might be the first manifestation of the production and further decay of a heavy CP-even Higgs resulting from a type-I Two Higgs Doublet Model. We demonstrate that in the presence of colored vector-like fermions, its gluon fusion production cross-section is strongly enhanced, with the enhancement depending on the color representation of the new fermion states. Our findings show that barring the color triplet case, any QCD "exotic" representation can fit the ATLAS result in fairly large portions of the parameter space. We have found that if the diboson excess is confirmed and this mechanism is indeed responsible for it, then the LHC Run-2 should find: (i) a CP-odd scalar with mass below ∼ 2.3 TeV, (ii) new colored states with masses below ∼ 2 TeV, (iii) no statistically significant diboson events in the W ± Z channel, (iv) events in the triboson channels W ± W ∓ Z and ZZZ with invariant mass amounting to the mass of the CP-odd scalar.

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LHC Signatures of Vector-Like Quarks

Cited by 91 publications

References 143 publications

Interplay of vector-like top partner multiplets in a realistic mixing set-up

Interplay of vector-like top partner multiplets in a realistic mixing set-up

Analysis of events with b-jets and a pair of leptons of the same charge in pp collisions at s = 8 $$ \sqrt{s}=8 $$ TeV with the ATLAS detector

Diboson anomaly: Heavy Higgs resonance and QCD vectorlike exotics

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