Abstract

Single top-quark t-channel production is exploited for studies of top quark properties. The analyses include the measurement of the CKM matrix element, |Vtb|, search for anomalous couplings of the top quark using a Bayesian neural network analysis, measurement of single top-quark polarization which directly confirms the V-A nature of the tWb production vertex, and the measurement of W-helicity fractions in the phase space sampled by a selection optimized for t-channel single top-quark production, orthogonal to the tt‾ final states used in traditional measurements of these properties. All measurements are found to be consistent with the standard model predictions.

Highlights

  • The top quark is the most massive particle known to date

  • All three production modes are sensitive to tWb-vertex and new physics

  • TW- or s-channel production is useful in W and charged Higgs searches and t-channel production can be used to look for flavor changing neutral currents (FCNCs)

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Summary

Introduction

The top quark is the most massive particle known to date. The top quark decays via the weak interaction and due to its high mass, it has a very short lifetime which is smaller than the hadronization time-scale, 1/ΛQCD. These measurements are sensitive to the tWb-vertex both in production and in decay. Using the fact that |Vtb| is much larger than |Vtd| and |Vts|, an anomalous coupling at the tWb-vertex can be parametrized by fVL and can be related to the measured (σt−ch.) and the theoretical (σtt−hecoh..) t-channel cross sections using the following equation. |V | tb Figure 3: Summary of |Vtb| measurements made by CMS

Anomalous Couplings in the t-channel Single-Top Production
Top Quark Polarization
W Helicity Fractions in Single Top-Quark Topologies
Summary and Conclusions

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