Eur. Phys. J. C (2007) 49: 791-801
https://doi.org/10.1140/epjc/s10052-006-0137-y

Regular Article - Theoretical Physics

Is V_tb≃1?

Centre for Particle Physics and Phenomenology (CP3), Université Catholique de Louvain, Chemin du Cyclotron 2, 1348, Louvain-la-Neuve, Belgium

^* e-mail: ekou@fyma.ucl.ac.be

Received: 28 July 2006
Revised: 19 September 2006
Published online: 2 December 2006

Abstract

The strongest constraint on V_tb presently comes from the 3×3 unitarity of the CKM matrix, which fixes V_tb to be very close to one. If unitarity is relaxed, current information from top production at Tevatron still leaves open the possibility that V_tb is sizably smaller than one. In minimal extensions of the standard model with extra heavy quarks, the unitarity constraints are much weaker, and the EW precision parameters entail the strongest bounds on V_tb. We discuss the experimental perspectives of discovering and identifying such new physics models at the Tevatron and the LHC, through a precise measurement of V_tb from the single top cross sections and by the study of processes where the extra heavy quarks are produced.