The branching ratio Rb in the littlest Higgs model

In the context of the littlest Higgs (LH) model, we study the contributions of the new particles to the branching ratio R-b. We find that the contributions mainly dependent on the free parameters f, c' and XL. The precision measurement value of Rb gives severe constraints on these free parameters. (C) 2004 Elsevier B.V. All rights reserved.