Higgs mass constraints on a fourth family: Upper and lower limits on CKM mixing

Chanowitz, Michael S.

doi:10.1103/physrevd.82.035018

Cited by 26 publications

(15 citation statements)

References 76 publications

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“…[1,2] for reviews. It is now common knowledge that a fourth family is not excluded by electroweak precision constraints [3][4][5][6][7][8][9][10][11] or by flavor constraints [12][13][14][15][16][17]. Moreover, this extension (SM4) of the standard model also offers several desired features:…”

Section: Introductionmentioning

confidence: 99%

Fourth generation Majorana neutrinos

2012

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We investigate the possibility of a fourth sequential generation in the lepton sector. Assuming neutrinos to be Majorana particles and starting from a recent-albeit weak-hint for a nonzero admixture of a fourth generation neutrino from fits to weak lepton and meson decays, we discuss constraints from neutrinoless double beta decay, radiative lepton decay, and like-sign dilepton production at hadron colliders. Also, an idea for fourth generation neutrino mass model building is briefly outlined. Here we soften the large hierarchy of the neutrino masses within an extradimensional model that locates each generation on different lepton number violating branes without large hierarchies.

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Section: Introductionmentioning

confidence: 99%

Fourth generation Majorana neutrinos

2012

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“…We shall assume that the dominant decay modes for these two heavy quarks are t ′ → W b and b ′ → tW → W W b, which is consistent with current bounds [6,7]. It is known that the multivariate analysis methods [8], like the neural network method and the boost decision tree method, can be quite useful to separate signal to background.…”

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confidence: 89%

Searches for thet′of a fourth family

Holdom

Yan

2011

Phys. Rev. D

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We study the detection of the t ′ of a fourth family during the early running of LHC with 7 TeV collision energy and 1 fb −1 integrated luminosity. By use of a neural network we show that it is feasible to search for the t ′ even with a mass close to the unitarity upper bound, which is in the 500 to 600 GeV range. We also present results for the Tevatron with 10 fb −1 . In both cases the search for a fourth family quark doublet can be significantly enhanced if one incorporates the contribution that the b ′ can make to a t ′ -like signal. Thus the bound on the mass of a degenerate quark doublet should be stronger than the bounds obtained by treating t ′ and b ′ in isolation.

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“…The expressions for Y 0 , S 0 , C 0 , D 0 and E 0 can be found in Appendix A, and H(x) is given in (3. 15). Note that D 0 (x) and E 0 (x) diverge logarithmically for x → 0, but G 0 (x) vanishes for x → 0.…”

Section: Four-lepton Transitionsmentioning

confidence: 99%

Lepton flavour violation in the presence of a fourth generation of quarks and leptons

Buras

Duling

Feldmann

et al. 2010

J. High Energ. Phys.

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We calculate the rates for the charged lepton flavour violating (LFV) decays i → j γ, τ → π, τ → η ( ) , µ − → e − e + e − , the six three-body leptonic decays τ − → − i + j − k and the rate for µ − e conversion in nuclei in the Standard Model (SM3) extended by a fourth generation of quarks and leptons (SM4), assuming that neutrinos are Dirac particles. We also calculate branching ratios for K L → µe, K L → π 0 µe, B d,s → µe, B d,s → τ e and B d,s → τ µ. We find that the pattern of the LFV branching ratios in the SM4 differs significantly from the one encountered in the MSSM, allowing to distinguish these two models with the help of LFV processes in a transparent manner. Also differences with respect to the Littlest Higgs model with T-parity are found. Most importantly the branching ratioscan all still be as large as the present experimental upper bounds but not necessarily simultaneously. Also the rate for µ − e conversion in nuclei can reach the corresponding upper bound.

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Higgs mass constraints on a fourth family: Upper and lower limits on CKM mixing

Cited by 26 publications

References 76 publications

Fourth generation Majorana neutrinos

Fourth generation Majorana neutrinos

Searches for thet′of a fourth family

Lepton flavour violation in the presence of a fourth generation of quarks and leptons

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