The branching ratio $R_{b}$ 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 $x_{L}$. The precision measurement value of $R_{b}$ gives severe constraints on these free parameters.