Less space for a new family of fermions

Journal Article · Mon Nov 01 00:00:00 EDT 2010 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PHYSREVD.82.095006· OSTI ID:21503822

Eberhardt, Otto ^[1]; Lenz, Alexander ^[1]; Rohrwild, Juergen ^[2]

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1. Institut fuer Theoretische Physik, Universitaet Regensburg, D-93040 Regensburg (Germany)
2. Institut fuer Theoretische Teilchenphysik und Kosmologie, RWTH Aachen University, D-52056 Aachen (Germany)

We investigate the experimentally allowed parameter space of an extension of the standard model (SM3) by one additional family of fermions. Therefore we extend our previous study of the Cabibbo-Kobayashi-Maskawa (CKM)-like mixing constraints of a fourth generation of quarks. In addition to the bounds from tree-level determinations of the 3x3 CKM elements and flavor-changing neutral currents processes (K, D, B{sub d}, B{sub s} mixing and the decay b{yields}s{gamma}) we also investigate the electroweak S, T, U parameters, the angle {gamma} of the unitarity triangle, and the rare decay B{sub s}{yields}{mu}{sup +}{mu}{sup -}. Moreover we improve our treatment of the QCD corrections compared to our previous analysis. We also take leptonic contributions into account, but we neglect the mixing among leptons. As a result we find that typically small mixing with the fourth family is favored, but still some sizeable deviations from the SM3 results are not yet excluded. The minimal possible value of V{sub tb} is 0.93. Also very large CP-violating effects in B{sub s} mixing seem to be impossible within an extension of the SM3 that consists of an additional fermion family alone. We find a delicate interplay of electroweak and flavor observables, which strongly suggests that a separate treatment of the two sectors is not feasible. In particular we show that the inclusion of the full CKM dependence of the S and T parameters in principle allows the existence of a degenerate fourth generation of quarks.

• OSTI ID: 21503822
• Journal Information: Physical Review. D, Particles Fields, Vol. 82, Issue 9; Other Information: DOI: 10.1103/PhysRevD.82.095006; (c) 2010 American Institute of Physics; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
B S MESONS
CORRECTIONS
CP INVARIANCE
FLAVOR MODEL
KOBAYASHI-MASKAWA MATRIX
MIXING
MUONS MINUS
MUONS PLUS
NEUTRAL CURRENTS
PARTICLE DECAY
QUANTUM CHROMODYNAMICS
QUARKS
STANDARD MODEL
UNITARITY
WEINBERG-SALAM GAUGE MODEL
ALGEBRAIC CURRENTS
ANTILEPTONS
ANTIMATTER
ANTIPARTICLES
BEAUTY MESONS
BEAUTY PARTICLES
BOSONS
COMPOSITE MODELS
CURRENTS
DECAY
ELEMENTARY PARTICLES
FERMIONS
FIELD THEORIES
GRAND UNIFIED THEORY
HADRONS
INVARIANCE PRINCIPLES
LEPTONS
MATHEMATICAL MODELS
MATRICES
MATTER
MESONS
MUONS
PARTICLE MODELS
PSEUDOSCALAR MESONS
QUANTUM FIELD THEORY
QUARK MODEL
STRANGE MESONS
STRANGE PARTICLES
UNIFIED GAUGE MODELS
UNIFIED-FIELD THEORIES