The study of the contribution of the LHT model to Zbb¯ coupling

In the framework of the Littlest Higgs model with T-parity (LHT), we study the contributions of the new particles to Zbb¯ couplings at one-loop level. Based on these results, we further study the branching ratio Rb and the unpolarized forward-backward asymmetry AFBb. We find that the correction of the new particles to Zbb¯ couplings is mainly on the left-handed coupling and has small part of the parameter space to alleviate the deviation between theoretical predictions and experimental values. The precision measurement value of Rb can give severe constraints on the relevant parameters. The constraints from the precision measurement value of AFBb are very weak.