Model Independent Constraints Among the Wtb, Zbb, and Ztt Couplings

TL;DR

This paper uses an effective Lagrangian approach to analyze the relationships among Wtb, Zbb, and Ztt couplings, revealing model-independent patterns of deviations constrained by experimental data and implications for collider measurements.

Contribution

It provides a model-independent analysis of electroweak couplings, showing how the standard model symmetry constrains deviations regardless of new physics models.

Findings

Pattern of deviations dictated by electroweak symmetry

Potential to determine Wtb coupling without knowing |V_{tb}|

Implications for collider measurements of top quark interactions

Abstract

Using an effective Lagrangian approach, we perform a model-independent analysis of the interactions among electroweak gauge bosons and the third generation quarks, i.e. the Wtb, Ztt and Zbb couplings. After one imposes the known experimental constraint on the Z b_L b_L coupling, we show that the electroweak symmetry of the standard model specifies the pattern of deviations of the Z t_L t_L and W t_L b_L couplings, independent of underlying new physics scenarios. We study implications of the predicted pattern with data on the single top quark and Ztt associated production processes at the Large Hadron Collider. Such an analysis could in principle allow for a determination of the Wtb coupling without prior knowledge of |V_{tb}|, which is otherwise difficult to achieve.