Probing anomalous right-handed current in the Zbb̄ vertex

Motivated by −2σ deviation from the Standard Model prediction for the forward–backward asymmetry of Z→bb̄ decay in the LEP data, we explore the anomalous couplings of Zbb̄ vertex through the electroweak precision test extended by including AFBb. We introduce a new variable ϵ′b to measure the anomalous right-handed coupling in Zbb̄ vertex. Implication of our analysis on the nonuniversal contact interactions is studied and the left-right model is also considered as a possible origin of the anomalous right-handed couplings.