Combined search for the quarks of a sequential fourth generation

• Main Authors: Apyan, Aram (Contributor), Bauer, Gerry P. (Contributor), Bendavid, Joshua L. (Contributor), Busza, Wit (Contributor), Butz, Erik M. (Contributor), Cali, Ivan Amos (Contributor), Chan, M. (Contributor), Dutta, V. (Contributor), Gomez-Ceballos, Guillelmo (Contributor), Goncharov, Maxim (Contributor), Hahn, Kristian Allan (Contributor), Kim, Y. (Contributor), Klute, Markus (Contributor), Krajczar, Krisztian F. (Contributor), Li, W. (Contributor), Luckey, P. David, Jr (Contributor), Ma, Teng (Contributor), Nahn, Steven (Contributor), Paus, Christoph M. E. (Contributor), Ralph, Duncan Kelley (Contributor), Roland, Christof E. (Contributor), Roland, Gunther M. (Contributor), Rudolph, M. (Contributor), Stephans, George S. F. (Contributor), Stockli, Fabian (Contributor), Sumorok, Konstanty C. (Contributor), Sung, Kevin Kai Hong (Contributor), Velicanu, Dragos Alexandru (Contributor), Wenger, Edward Allen (Contributor), Wolf, R. (Contributor), Wyslouch, Boleslaw (Contributor), Yang, M. (Contributor), Yilmaz, Yetkin (Contributor), Yoon, A. S. (Contributor), Zanetti, Marco (Contributor)
• Other Authors: Massachusetts Institute of Technology. Department of Physics (Contributor), Massachusetts Institute of Technology. Laboratory for Nuclear Science (Contributor), Massachusetts Institute of Technology. School of Science (Contributor)
• Format: Article
• Language: English
• Published: American Physical Society, 2013-02-13T22:15:37Z.
• Subjects: Article
• Online Access: Get fulltext

 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.