The Study of the contribution of the LHT model to $Zb\bar{b}$ coupling

Abstract

In the framework of the Littlest Higgs Model with T-parity (LHT), we study the contributions of the new particles to $Zb\bar{b}$ couplings at one-loop level. Based on these results, we further study the branching ratio $R_b$ and the unpolarized forward-backward asymmetry $A_{FB}^b$. We find that the correction of the new particles to $Zb\bar{b}$ 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 $R_b$ can give severe constraints on the relevant parameters. The constraints from the precision measurement value of $A_{FB}^b$ are very weak.

20 pages, 23 figures