Extra quark-lepton generations and precision measurements

Maltoni, Michele; Novikov, V.A.; Okun, L.B.; Rozanov, Alexandre; Vysotsky, M. I.

doi:10.1016/s0370-2693(00)00109-x

Cited by 109 publications

(154 citation statements)

References 17 publications

(16 reference statements)

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“…Therefore, additional fermion families are needed to satisfy the condition (6). It is known that recent precision electroweak data allows the existence of the fourth SM family [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. In this case to satisfy the above condition in our model we take lepton charge of the fourth family leptons is equal to −3 [13,34].…”

Section: The Modelmentioning

confidence: 99%

A search for leptophilic Z l boson at future linear colliders

Kara

Sahin

Sultansoy

et al. 2011

J. High Energ. Phys.

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Section: The Modelmentioning

confidence: 99%

A search for leptophilic Z l boson at future linear colliders

Kara

Sahin

Sultansoy

et al. 2011

J. High Energ. Phys.

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“…Ref. [16] used an unconventional formalism for analyzing the oblique corrections and a detailed comparison is difficult. Our analysis, based on the standard (S, T, U) formalism [6], is transparent and can be readily applied to a given model.…”

Section: B Lepton and Quark Sectormentioning

confidence: 99%

Extra families, Higgs spectrum, and oblique corrections

2001

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The standard model accommodates, but does not explain, three families of leptons and quarks, while various extensions suggest extra matter families. The oblique corrections from extra chiral families with relatively light (weakscale) masses, M f ∼ H , are analyzed and used to constrain the number of extra families and their spectrum. The analysis is motivated, in part, by recent N = 2 supersymmetry constructions, but is performed in a modelindependent way. It is shown that the correlations among the contributions to the three oblique parameters, rather than the contribution to a particular one, provide the most significant bound. Nevertheless, a single extra chiral family with a constrained spectrum is found to be consistent with precision data without requiring any other new physics source. Models with three additional families may also be accommodated but only by invoking additional new physics, most notably, a two-Higgs-doublet extension. The interplay between the spectra of the extra fermions and the Higgs boson(s) is analyzed in the case of either one or two Higgs doublets, and its implications are explored. In particular, the precision bound on the SM-like Higgs boson mass is shown to be significantly relaxed in the presence of an extra relatively light chiral family.

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“…These significant results are primarily based on numerical scans, with emphasis on the role of a lighter neutrino (50 GeV) to minimize the contributions to the oblique parameters (see also Ref. [5]). However, a neutrino with mass of 50 GeV, if unstable, is ruled out by LEP II bounds, while if it exactly stable, may be ruled out by dark matter direct search experiments [6].…”

Section: Introductionmentioning

confidence: 99%

Four generations and Higgs physics

et al. 2007

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In the light of the LHC, we revisit the implications of a fourth generation of chiral matter. We identify a specific ensemble of particle masses and mixings that are in agreement with all current experimental bounds as well as minimize the contributions to electroweak precision observables. Higgs masses between 115-315 (115-750) GeV are allowed by electroweak precision data at the 68% and 95% CL. Within this parameter space, there are dramatic effects on Higgs phenomenology: production rates are enhanced, weak-boson-fusion channels are suppressed, angular distributions are modified, and Higgs pairs can we observed. We also identify exotic signals, such as Higgs decay to same-sign dileptons. Finally, we estimate the upper bound on the cutoff scale from vacuum stability and triviality.

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Extra quark-lepton generations and precision measurements

Cited by 109 publications

References 17 publications

A search for leptophilic Z l boson at future linear colliders

A search for leptophilic Z l boson at future linear colliders

Extra families, Higgs spectrum, and oblique corrections

Four generations and Higgs physics

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