Constraints on the four-generation quark mixing matrix from a fit to flavor-physics data

Alok, Ashutosh Kumar; Dighe, Amol; London, David

doi:10.1103/physrevd.83.073008

Cited by 50 publications

(37 citation statements)

References 107 publications

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“…For example, the mixing parameters for the quark sector may be constrained [2,39] with data from neutral mesons, the b → sγ transition, existing constraints on the three-generation quark mixing matrix and limits on Br(B S →µ + µ − ). Reference [39] concludes that large mixings of the fourth generation with the three known generations are not ruled out, but [40,41], which considers constraints from corrections to the Z →bb vertex from a fourth generation conclude that these mixings could be comparable to Cabibbo mixing. The quark mixing matrix can also be constrained with precision electroweak data and D 0 − D 0 mixing [42].…”

Section: A Methodsmentioning

confidence: 99%

Masses of a fourth generation with two Higgs doublets

et al. 2012

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We use sampling techniques to find robust constraints on the masses of a possible fourth sequential fermion generation from electroweak oblique variables. We find that in the case of a light (115 GeV) Higgs from a single electroweak symmetry breaking doublet, inverted mass hierarchies are possible for both quarks and leptons, but a mass splitting more than MW in the quark sector is unlikely. We also find constraints in the case of a heavy (600 GeV) Higgs in a single doublet model. As recent data from the Large Hadron Collider hints at the existence of a resonance at 124.5 GeV and a single Higgs doublet at that mass is inconsistent with a fourth fermion generation, we examine a type II two Higgs doublet model. In this model, there are ranges of parameter space where the Higgs sector can potentially counteract the effects of the fourth generation. Even so, we find that such scenarios produce qualitatively similar fermion mass distributions.

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Section: A Methodsmentioning

confidence: 99%

Masses of a fourth generation with two Higgs doublets

et al. 2012

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“…Therefore, which decay is dominant depends sensitively on the KK scale R −1 and also on the CKM mixing V t b . In particular, for R −1 = 1.5 TeV and V t b = 0.1 (a value favored in the fits of [26]), the branching ratio for t → t h seems to be predicted to be dominant and about twice as large as the one for t → b W over the allowed parameter space. While for R −1 = 3 TeV and V t b = 0.1, the branching ratio for In all three plots, the flavor violating decay t → tZ 0 is subdominant, yet non-negligible either, with possible branchings ranging from about 1% to 10%.…”

Section: One-loop Processesmentioning

confidence: 99%

“…In the first possibility, q stands for t if kinematically allowed, and for c or u. The partial width of these channels depend on the size of the CKM4 angles V tb , V cb and V ub which are typically constrained to be small [26]. A channel which could compete is b → b Z 0 , since in the RS scenario under study these flavor violating couplings appear at tree-level, in a similar fashion as in the Higgs sector [5,44].…”

Section: One-loop Processesmentioning

confidence: 99%

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Higgs phenomenology in warped extra dimensions with a fourth generation

Frank¹,

Korutlu²,

Toharia³

2011

Phys. Rev. D

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We study a warped extra-dimension scenario where the Standard Model fields lie in the bulk, with the addition of a fourth family of fermions. We concentrate on the flavor structure of the Higgs couplings with fermions in the flavor anarchy ansatz. Even without a fourth family, these couplings will be generically misaligned with respect to the SM fermion mass matrices. The presence of the fourth family typically enhances the misalignment effects and we show that one should expect them to be highly non-symmetrical in the (34) inter-generational mixing. The radiative corrections from the new fermions and their flavor violating couplings to the Higgs affect negligibly known experimental precision measurements such as the oblique parameters and Z → bb or Z → µ + µ − .On the other hand, ∆F = 1, 2 processes, mediated by tree-level Higgs exchange, as well as radiative corrections to b → sγ and µ → eγ put some generic pressure on the allowed size of the flavor violating couplings. But more importantly, these couplings will alter the Higgs decay patterns as well as those of the new fermions, and produce very interesting new signals associated to Higgs phenomenology in high energy colliders. These might become very important indirect signals for these type of models as they would be present even when the KK mass scale is high and no heavy KK particle is discovered.

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“…The SM4 and VdQ models were examined in Refs. [4] and [10], respectively. In the present paper we consider the VuQ model [14,15], in which the full CKM matrix is 4 × 3.…”

Section: Introductionmentioning

confidence: 99%

New-physics signals of a model with a vector-singlet up-type quark

Umasankar¹,

Alok²,

Banerjee³

et al. 2016

Proceedings of the European Physical Society Conference on High Energy Physics — PoS(EPS-HEP2015)

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The VuQ model involves the addition of a vector isosinglet up-type quark to the standard model. In this model the full CKM quark mixing matrix is 4 × 3. Using present flavor-physics data, we perform a fit to this full CKM matrix, looking for signals of new physics (NP). We find that the VuQ model is very strongly constrained. There are no hints of NP in the CKM matrix, and any VuQ contributions to loop-level flavor-changing b → s, b → d and s → d transitions are very small. There can be significant enhancements of the branching ratios of the flavor-changing decays t → uZ and t → cZ, but these are still below present detection levels.

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Constraints on the four-generation quark mixing matrix from a fit to flavor-physics data

Cited by 50 publications

References 107 publications

Masses of a fourth generation with two Higgs doublets

Masses of a fourth generation with two Higgs doublets

Higgs phenomenology in warped extra dimensions with a fourth generation

New-physics signals of a model with a vector-singlet up-type quark

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