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Combined search for the quarks of a sequential fourth generation


CMS Collaboration; Chatrchyan, S; Khachatryan, V; Sirunyan, A M; Tumasyan, A; Amsler, C; Chiochia, V; De Visscher, S; Favaro, C; Ivova Rikova, M; Millan Mejias, B; Otiougova, P; Robmann, P; Snoek, H; Tupputi, S; Verzetti, M (2012). Combined search for the quarks of a sequential fourth generation. Physical Review D (Particles, Fields, Gravitation and Cosmology), 86(11):112003.

Abstract

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.

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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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Physics Institute
Dewey Decimal Classification:530 Physics
Language:English
Date:2012
Deposited On:08 Mar 2013 09:19
Last Modified:05 Apr 2016 16:39
Publisher:American Physical Society
ISSN:1550-2368
Publisher DOI:https://doi.org/10.1103/PhysRevD.86.112003
Permanent URL: https://doi.org/10.5167/uzh-76098

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