The Dynamical Models and the Z -> b¯ {b} Asymmetry

Motivated by the 3.2σ (1.4σ) deviations between the recent experimental value for A_FB^b(R_b) and the standard model (SM) prediction, we examine the effect of new physics (NP) on the Zb¯ {b} couplings g_L^b and g_R^b. First we focus our attention on the dynamical models. Then, using effective Lagrangian techniques, we discuss the corrections of NP to g_L^b and g_R^b. We find some kinds of NP which might explain the recently experimental data about R_b and A_FB ^b. However, the free parameters of these kinds of NP must be severely constrained.