Combined search for the quarks of a sequential fourth generation
Author(s)
Apyan, Aram; Bauer, Gerry P.; Bendavid, Joshua L.; Busza, Wit; Butz, Erik M.; Cali, Ivan Amos; Chan, M.; Dutta, V.; Gomez-Ceballos, Guillelmo; Goncharov, Maxim; Hahn, Kristian Allan; Kim, Y.; Klute, Markus; Krajczar, Krisztian F.; Li, W.; Luckey, P. David, Jr.; Ma, Teng; Nahn, Steven; Paus, Christoph M. E.; Ralph, Duncan Kelley; Roland, Christof E.; Roland, Gunther M.; Rudolph, M.; Stephans, George S. F.; Stockli, Fabian; Sumorok, Konstanty C.; Sung, Kevin Kai Hong; Velicanu, Dragos Alexandru; Wenger, Edward Allen; Wolf, R.; Wyslouch, Boleslaw; Yang, M.; Yilmaz, Yetkin; Yoon, A. S.; Zanetti, Marco; ... Show more Show less
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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[superscript -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.
Date issued
2012-12Department
Massachusetts Institute of Technology. Department of Physics; Massachusetts Institute of Technology. Laboratory for Nuclear Science; Massachusetts Institute of Technology. School of ScienceJournal
Physical Review D
Publisher
American Physical Society
Citation
Chatrchyan, S. et al. “Combined Search for the Quarks of a Sequential Fourth Generation.” Physical Review D 86.11 (2012). © 2012 CERN, for the CMS Collaboration
Version: Final published version
ISSN
1550-7998
1089-4918