Status of the fourth fermion generation before ICHEP2012: Higgs data and electroweak precision observables

We perform a global fit of the parameters of the Standard Model with a sequential fourth generation (SM4) to LHC and Tevatron Higgs data and electroweak precision data. We find that the minimal chi-square value of the SM4 is larger than that of the Standard Model with three generations (SM3) by 8 un...

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Detalles Bibliográficos
Autores principales: Eberhardt, Otto, Lenz, Alexander, Menzel, Andreas, Nierste, Ulrich, Wiebusch, Martin
Lenguaje:eng
Publicado: 2012
Materias:
Particle Physics - Phenomenology
Acceso en línea:https://dx.doi.org/10.1103/PhysRevD.86.074014
http://cds.cern.ch/record/1459329
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author Eberhardt, Otto
Lenz, Alexander
Menzel, Andreas
Nierste, Ulrich
Wiebusch, Martin
author_facet Eberhardt, Otto
Lenz, Alexander
Menzel, Andreas
Nierste, Ulrich
Wiebusch, Martin
author_sort Eberhardt, Otto
collection CERN
description We perform a global fit of the parameters of the Standard Model with a sequential fourth generation (SM4) to LHC and Tevatron Higgs data and electroweak precision data. We find that the minimal chi-square value of the SM4 is larger than that of the Standard Model with three generations (SM3) by 8 units. We then perform several likelihood ratio tests which compare the the performance of the SM4 and SM3 at describing the measured data. Since the SM3 and SM4 are not nested (i.e. the SM3 can not be considered as a special case of the SM4 with some parameters fixed) the usual analytical formulae for p-values in likelihood ratio tests do not hold. We thus apply a new method to compute these p-values. For a Higgs mass of 126.5 GeV we find that the SM4 is excluded at 3.1 sigma.
id cern-1459329
institution Organización Europea para la Investigación Nuclear
language eng
publishDate 2012
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spelling cern-14593292020-06-22T19:27:46Zdoi:10.1103/PhysRevD.86.074014http://cds.cern.ch/record/1459329engEberhardt, OttoLenz, AlexanderMenzel, AndreasNierste, UlrichWiebusch, MartinStatus of the fourth fermion generation before ICHEP2012: Higgs data and electroweak precision observablesParticle Physics - PhenomenologyWe perform a global fit of the parameters of the Standard Model with a sequential fourth generation (SM4) to LHC and Tevatron Higgs data and electroweak precision data. We find that the minimal chi-square value of the SM4 is larger than that of the Standard Model with three generations (SM3) by 8 units. We then perform several likelihood ratio tests which compare the the performance of the SM4 and SM3 at describing the measured data. Since the SM3 and SM4 are not nested (i.e. the SM3 can not be considered as a special case of the SM4 with some parameters fixed) the usual analytical formulae for p-values in likelihood ratio tests do not hold. We thus apply a new method to compute these p-values. For a Higgs mass of 126.5 GeV we find that the SM4 is excluded at 3.1 sigma.We perform a global fit of the parameters of the Standard Model with a sequential fourth generation (SM4) to LHC and Tevatron Higgs data and electroweak precision data. Using several likelihood ratio tests we compare the performance of the SM4 and SM3 at describing the measured data. Since the SM3 and SM4 are not nested (i.e. the SM3 can not be considered as a special case of the SM4 with some parameters fixed) the usual analytical formulae for p-values in likelihood ratio tests do not hold. We thus apply a new method to compute these p-values. For a Higgs mass of 126.5 GeV and fourth-generation quark masses above 600 GeV we find that the SM4 is excluded at 3.1 sigma.arXiv:1207.0438TTP12-023CERN-PH-TH-2012-182TTP12-023CERN-PH-TH-2012-182oai:cds.cern.ch:14593292012-07-03
spellingShingle Particle Physics - Phenomenology
Eberhardt, Otto
Lenz, Alexander
Menzel, Andreas
Nierste, Ulrich
Wiebusch, Martin
Status of the fourth fermion generation before ICHEP2012: Higgs data and electroweak precision observables
title Status of the fourth fermion generation before ICHEP2012: Higgs data and electroweak precision observables
title_full Status of the fourth fermion generation before ICHEP2012: Higgs data and electroweak precision observables
title_fullStr Status of the fourth fermion generation before ICHEP2012: Higgs data and electroweak precision observables
title_full_unstemmed Status of the fourth fermion generation before ICHEP2012: Higgs data and electroweak precision observables
title_short Status of the fourth fermion generation before ICHEP2012: Higgs data and electroweak precision observables
title_sort status of the fourth fermion generation before ichep2012: higgs data and electroweak precision observables
topic Particle Physics - Phenomenology
url https://dx.doi.org/10.1103/PhysRevD.86.074014
http://cds.cern.ch/record/1459329
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AT lenzalexander statusofthefourthfermiongenerationbeforeichep2012higgsdataandelectroweakprecisionobservables
AT menzelandreas statusofthefourthfermiongenerationbeforeichep2012higgsdataandelectroweakprecisionobservables
AT niersteulrich statusofthefourthfermiongenerationbeforeichep2012higgsdataandelectroweakprecisionobservables
AT wiebuschmartin statusofthefourthfermiongenerationbeforeichep2012higgsdataandelectroweakprecisionobservables

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