The Top Quark Decay Vertex in Standard Model Extensions

TL;DR

This paper examines how new physics models like two-Higgs doublets, supersymmetry, and technicolor influence the top quark's decay vertex, revealing small but notable deviations from the Standard Model predictions.

Contribution

It provides a comparative analysis of anomalous top decay couplings across multiple beyond Standard Model theories, highlighting potential observable effects.

Findings

Anomalous couplings are below 1% in two-Higgs and supersymmetric models.

Technicolor interactions can reduce the left-chiral coupling by several percent.

The study offers insights into potential deviations in top quark decay measurements.

Abstract

New physics interactions can affect the strength and structure of the $tbW$ vertex. We investigate the magnitudes and phases of "anomalous" contributions to this vertex in a two-Higgs doublet and the minimal supersymmetric extension of the standard model, and in a top-color assisted technicolor (TC2) model. While the magnitudes of the anomalous couplings remain below 1 percent in the first two models, TC2 interactions can reduce the left-chiral coupling $f_L$ by several percent.