Analysis of tbW and ttZ couplings from CLEO and LEP/SLC data

TL;DR

This paper updates constraints on anomalous tbW and ttZ couplings using data from CLEO and LEP/SLC, finding very tight bounds and limited explanation for certain asymmetry deviations.

Contribution

It provides the most recent and stringent bounds on anomalous tbW and ttZ couplings from precision electroweak data.

Findings

Stringent bounds on anomalous couplings from data

Limited explanation for asymmetry deviations

Strong constraints reduce new physics possibilities

Abstract

We update the constraints on anomalous dimension four $\tbw$ and $\ttz$ couplings by using CLEO $b \ra s \gamma$ and LEP/SLC precision $Z$-pole data. It is found that the data imposes very stringent bounds on them. Moreover, the $2 \sigma$ pull from SM predictions of $A_{LR}$(hadrons), $A_b$ and $A_{FB}$(b) have little chance of being explained by the strongly constrained anomalous couplings.