The Experts below are selected from a list of 276 Experts worldwide ranked by ideXlab platform
C. D. Froggatt - One of the best experts on this subject based on the ideXlab platform.
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Supersymmetric grand unification with a Fourth Generation
Physics Letters B, 2003Co-Authors: J. E. Dubicki, C. D. FroggattAbstract:Abstract The possibility of incorporating a chiral Fourth Generation into a SUSY-GUT is investigated. Precision fits to electroweak observables require us to introduce light supersymmetric particles, with masses less than M Z . These particles might also provide decay channels for the Fourth Generation quarks of mass ∼ 100 GeV. We also require tan β to lie in the range 1.50 ≲tan β ≲ 1.75 and obtain an upper limit on the lightest Higgs boson mass in the MSSM4 of 152 GeV.
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Supersymmetric grand unification with a Fourth Generation?
Physics Letters B, 2003Co-Authors: J. E. Dubicki, C. D. FroggattAbstract:The possibility of incorporating a chiral Fourth Generation into a SUSY-GUT is investigated. Precision fits to electroweak observables require us to introduce light supersymmetric particles, with masses less than M/sub Z/. These particles might also provide decay channels for the Fourth Generation quarks of mass ~100 GeV. We also require tan beta to lie in the range 1.50 lt or approximately=tan beta 1.75 and obtain an upper limit on the lightest Higgs boson mass in the MSSM4 of 152 GeV
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Could there be a Fourth Generation
arXiv: High Energy Physics - Phenomenology, 2002Co-Authors: C. D. Froggatt, J. E. DubickiAbstract:We investigate the possibility of incorporating a chiral Fourth Generation into a GUT model. We find that in order to do so, precision fits to electroweak observables demand the introduction of light (< M_Z) supersymmetric particles. This also enables us to provide decay channels to the Fourth-Generation quarks. Perturbative consistency sets an upper bound on the coloured supersymmetric spectrum. The upper limit on the lightest Higgs boson is calculated and found to be above the present experimental lower limit.
J. E. Dubicki - One of the best experts on this subject based on the ideXlab platform.
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Supersymmetric grand unification with a Fourth Generation
Physics Letters B, 2003Co-Authors: J. E. Dubicki, C. D. FroggattAbstract:Abstract The possibility of incorporating a chiral Fourth Generation into a SUSY-GUT is investigated. Precision fits to electroweak observables require us to introduce light supersymmetric particles, with masses less than M Z . These particles might also provide decay channels for the Fourth Generation quarks of mass ∼ 100 GeV. We also require tan β to lie in the range 1.50 ≲tan β ≲ 1.75 and obtain an upper limit on the lightest Higgs boson mass in the MSSM4 of 152 GeV.
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Supersymmetric grand unification with a Fourth Generation?
Physics Letters B, 2003Co-Authors: J. E. Dubicki, C. D. FroggattAbstract:The possibility of incorporating a chiral Fourth Generation into a SUSY-GUT is investigated. Precision fits to electroweak observables require us to introduce light supersymmetric particles, with masses less than M/sub Z/. These particles might also provide decay channels for the Fourth Generation quarks of mass ~100 GeV. We also require tan beta to lie in the range 1.50 lt or approximately=tan beta 1.75 and obtain an upper limit on the lightest Higgs boson mass in the MSSM4 of 152 GeV
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Could there be a Fourth Generation
arXiv: High Energy Physics - Phenomenology, 2002Co-Authors: C. D. Froggatt, J. E. DubickiAbstract:We investigate the possibility of incorporating a chiral Fourth Generation into a GUT model. We find that in order to do so, precision fits to electroweak observables demand the introduction of light (< M_Z) supersymmetric particles. This also enables us to provide decay channels to the Fourth-Generation quarks. Perturbative consistency sets an upper bound on the coloured supersymmetric spectrum. The upper limit on the lightest Higgs boson is calculated and found to be above the present experimental lower limit.
Christian Fabjan - One of the best experts on this subject based on the ideXlab platform.
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Combined search for the quarks of a sequential Fourth Generation
Physical Review D, 2012Co-Authors: Serguei Chatrchyan, J. Erö, E Aguilo, Vardan Khachatryan, Marko Dragicevic, Tobias Bergauer, Albert M Sirunyan, Armen Tumasyan, Wolfgang Adam, Christian FabjanAbstract:Results are presented from a search for a Fourth Generation of quarks produced singly or in pairs in a data set corresponding to an integrated luminosity of 5 fb-1 recorded by the CMS experiment at the LHC in 2011. A novel strategy has been developed for a combined search for quarks of the up and down type in decay channels with at least one isolated muon or electron. Limits on the mass of the Fourth-Generation quarks and the relevant Cabibbo-Kobayashi-Maskawa matrix elements are derived in the context of a simple extension of the standard model with a sequential Fourth Generation of fermions. The existence of mass-degenerate Fourth-Generation quarks with masses below 685 GeV is excluded at 95% confidence level for minimal off-diagonal mixing between the third- and the Fourth-Generation quarks. With a mass difference of 25 GeV between the quark masses, the obtained limit on the masses of the Fourth-Generation quarks shifts by about ±20 GeV. These results significantly reduce the allowed parameter space for a Fourth Generation of fermions.
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Combined search for the quarks of a sequential Fourth Generation
Physical Review D - Particles Fields Gravitation and Cosmology, 2012Co-Authors: Serguei Chatrchyan, J. Erö, E Aguilo, Vardan Khachatryan, Marko Dragicevic, Tobias Bergauer, Albert M Sirunyan, Armen Tumasyan, Waldemar Adam, Christian FabjanAbstract:Results are presented from a search for a Fourth Generation of quarks produced singly or in pairs in a data set corresponding to an integrated luminosity of 5fb-1 recorded by the CMS experiment at the LHC in 2011. A novel strategy has been developed for a combined search for quarks of the up and down type in decay channels with at least one isolated muon or electron. Limits on the mass of the Fourth-Generation quarks and the relevant Cabibbo-Kobayashi-Maskawa matrix elements are derived in the context of a simple extension of the standard model with a sequential Fourth Generation of fermions. The existence of mass-degenerate Fourth-Generation quarks with masses below 685GeV is excluded at 95% confidence level for minimal off-diagonal mixing between the third- and the Fourth-Generation quarks. With a mass difference of 25GeV between the quark masses, the obtained limit on the masses of the Fourth-Generation quarks shifts by about ±20GeV. These results significantly reduce the allowed parameter space for a Fourth Generation of fermions. © 2012 CERN.
Serguei Chatrchyan - One of the best experts on this subject based on the ideXlab platform.
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Combined search for the quarks of a sequential Fourth Generation
Physical Review D, 2012Co-Authors: Serguei Chatrchyan, J. Erö, E Aguilo, Vardan Khachatryan, Marko Dragicevic, Tobias Bergauer, Albert M Sirunyan, Armen Tumasyan, Wolfgang Adam, Christian FabjanAbstract:Results are presented from a search for a Fourth Generation of quarks produced singly or in pairs in a data set corresponding to an integrated luminosity of 5 fb-1 recorded by the CMS experiment at the LHC in 2011. A novel strategy has been developed for a combined search for quarks of the up and down type in decay channels with at least one isolated muon or electron. Limits on the mass of the Fourth-Generation quarks and the relevant Cabibbo-Kobayashi-Maskawa matrix elements are derived in the context of a simple extension of the standard model with a sequential Fourth Generation of fermions. The existence of mass-degenerate Fourth-Generation quarks with masses below 685 GeV is excluded at 95% confidence level for minimal off-diagonal mixing between the third- and the Fourth-Generation quarks. With a mass difference of 25 GeV between the quark masses, the obtained limit on the masses of the Fourth-Generation quarks shifts by about ±20 GeV. These results significantly reduce the allowed parameter space for a Fourth Generation of fermions.
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Combined search for the quarks of a sequential Fourth Generation
Physical Review D - Particles Fields Gravitation and Cosmology, 2012Co-Authors: Serguei Chatrchyan, J. Erö, E Aguilo, Vardan Khachatryan, Marko Dragicevic, Tobias Bergauer, Albert M Sirunyan, Armen Tumasyan, Waldemar Adam, Christian FabjanAbstract:Results are presented from a search for a Fourth Generation of quarks produced singly or in pairs in a data set corresponding to an integrated luminosity of 5fb-1 recorded by the CMS experiment at the LHC in 2011. A novel strategy has been developed for a combined search for quarks of the up and down type in decay channels with at least one isolated muon or electron. Limits on the mass of the Fourth-Generation quarks and the relevant Cabibbo-Kobayashi-Maskawa matrix elements are derived in the context of a simple extension of the standard model with a sequential Fourth Generation of fermions. The existence of mass-degenerate Fourth-Generation quarks with masses below 685GeV is excluded at 95% confidence level for minimal off-diagonal mixing between the third- and the Fourth-Generation quarks. With a mass difference of 25GeV between the quark masses, the obtained limit on the masses of the Fourth-Generation quarks shifts by about ±20GeV. These results significantly reduce the allowed parameter space for a Fourth Generation of fermions. © 2012 CERN.
R. D. Matheus - One of the best experts on this subject based on the ideXlab platform.
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Lepton sector of a Fourth Generation
Physical Review D, 2010Co-Authors: Gustavo Burdman, L. Da Rold, R. D. MatheusAbstract:In extensions of the standard model with a heavy Fourth Generation, one important question is what makes the Fourth-Generation lepton sector, particularly the neutrinos, so different from the lighter three Generations. We study this question in the context of models of electroweak symmetry breaking in warped extra dimensions, where the flavor hierarchy is generated by choosing the localization of the zero-mode fermions in the extra dimension. In this setup the Higgs sector is localized near the infrared brane, whereas the Majorana mass term is localized at the ultraviolet brane. As a result, light neutrinos are almost entirely Majorana particles, whereas the Fourth-Generation neutrino is mostly a Dirac fermion. We show that it is possible to obtain heavy Fourth-Generation leptons in regions of parameter space where the light neutrino masses and mixings are compatible with observation. We study the impact of these bounds, as well as the ones from lepton flavor violation, on the phenomenology of these models.
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Strongly coupled Fourth Generation at the LHC
Physical Review D, 2009Co-Authors: Gustavo Burdman, L. Da Rold, Ojp Eboli, R. D. MatheusAbstract:We study extensions of the standard model with a strongly coupled Fourth Generation. This occurs in models where electroweak symmetry breaking is triggered by the condensation of at least some of the Fourth-Generation fermions. With focus on the phenomenology at the LHC, we study the pair production of Fourth-Generation down quarks, D{sub 4}. We consider the typical masses that could be associated with a strongly coupled fermion sector, in the range (300-600) GeV. We show that the production and successive decay of these heavy quarks into final states with same-sign dileptons, trileptons, and four leptons can be easily seen above background with relatively low luminosity. On the other hand, in order to confirm the presence of a new strong interaction responsible for Fourth-Generation condensation, we study its contribution to D{sub 4} pair production, and the potential to separate it from standard QCD-induced heavy quark production. We show that this separation might require large amounts of data. This is true even if it is assumed that the new interaction is mediated by a massive colored vector boson, since its strong coupling to the Fourth Generation renders its width of the order of its mass. We conclude that, although this class ofmore » models can be falsified at early stages of the LHC running, its confirmation would require high integrated luminosities.« less
