Combined search for the quarks of a sequential fourth generation
Physical Review D - Particles, Fields, Gravitation and Cosmology, vol.86, no.11, 2012 (SCI-Expanded, Scopus)
- Publication Type: Article / Article
- Volume: 86 Issue: 11
- Publication Date: 2012
- Doi Number: 10.1103/physrevd.86.112003
- Journal Name: Physical Review D - Particles, Fields, Gravitation and Cosmology
- Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
- Yıldız Technical University Affiliated: No
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 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.