Indirect Constraints on the Triple Gauge Boson Couplings from $Z \to b \bar{b}$ Partial Width: An Update

Abstract

We update the indirect bounds on anomalous triple gauge couplings coming from the non-universal one-loop contributions to the $Z \to b \bar{b}$ width. These bounds, which are independent of the Higgs boson mass, are in agreement with the standard model predictions for the gauge boson self-couplings since the present value of $R_b$ agrees fairly well with the theoretical estimates. Moreover, these indirect constraints on $\Delta g^Z_1$ and $g^Z_5$ are more stringent than the present direct bounds on these quantities, while the indirect limit on $\lambda_Z$ is weaker than the available experimental data.