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Single Top Quark Production and Decay at Next-to-leading Order in Hadron Collision

Qing-Hong Cao, C. -P. Yuan

TL;DR

This work provides a complete next-to-leading-order QCD calculation for both the production and decay of single top quarks at hadron colliders, incorporating spin correlations and a Breit–Wigner treatment of the top width through a modified narrow width approach. It employs a one-scale phase space slicing method and a comprehensive form-factor formalism to handle soft, collinear, and virtual corrections, ensuring fully differential predictions that can accommodate realistic experimental cuts. The analysis is performed in both DREG and DRED schemes to address the γ5 treatment and includes explicit LO and NLO helicity amplitudes for production and decay channels, with a structured categorization into INIT, FINAL, LIGHT, HEAVY, and decay corrections. The framework enables precise Standard Model tests of the W–t–b coupling, CKM element V_tb, and potential new physics effects via form-factor modifications, while providing a robust tool for collider phenomenology and experimental comparisons.

Abstract

We present a calculation of the next-to-leading order QCD corrections, with one-scale phase space slicing method, to single top quark production and decay process $p\bar{p},pp\to t\bar{b}+X\to b\ellν\bar{b}+X$ at hadron colliders. Using the helicity amplitude method, the angular correlation of the final state partons and the spin correlation of the top quark are preserved. The effect of the top quark width is also examined.

Single Top Quark Production and Decay at Next-to-leading Order in Hadron Collision

TL;DR

This work provides a complete next-to-leading-order QCD calculation for both the production and decay of single top quarks at hadron colliders, incorporating spin correlations and a Breit–Wigner treatment of the top width through a modified narrow width approach. It employs a one-scale phase space slicing method and a comprehensive form-factor formalism to handle soft, collinear, and virtual corrections, ensuring fully differential predictions that can accommodate realistic experimental cuts. The analysis is performed in both DREG and DRED schemes to address the γ5 treatment and includes explicit LO and NLO helicity amplitudes for production and decay channels, with a structured categorization into INIT, FINAL, LIGHT, HEAVY, and decay corrections. The framework enables precise Standard Model tests of the W–t–b coupling, CKM element V_tb, and potential new physics effects via form-factor modifications, while providing a robust tool for collider phenomenology and experimental comparisons.

Abstract

We present a calculation of the next-to-leading order QCD corrections, with one-scale phase space slicing method, to single top quark production and decay process at hadron colliders. Using the helicity amplitude method, the angular correlation of the final state partons and the spin correlation of the top quark are preserved. The effect of the top quark width is also examined.

Paper Structure

This paper contains 32 sections, 116 equations, 9 figures.

Table of Contents

  1. Introduction
  2. Outline of the calculation
  3. Narrow width approximation
  4. Phase space slicing method
  5. $\gamma_{5}$ problem
  6. Leading order results of single top quark production and decay process
  7. Helicity matrix elements of single top quark production
  8. Helicity matrix elements of top quark decay
  9. NLO matrix elements of Single top quark production and decay processes
  10. Categorizing the single top quark processes
  11. Form factor formalism for SCV corrections
  12. INIT form factors
  13. FINAL form factors
  14. LIGHT form factors
  15. HEAVY form factors
  16. ...and 17 more sections

Figures (9)

  • Figure 1: Feynman diagrams of the Born level contribution to the production and decay of single top quark. (a) s-channel (b) t-channel
  • Figure 2: Illustration of the PSS method with one cutoff scale to describe the processes with initial state massless quarks. Here, only half of the real emission diagrams is shown. In this paper, we assign the particle's momentum such that the initial state particle's momentum is incoming to the vertex while the final state particle's momentum is outgoing.
  • Figure 3: The way we organize our calculations at the NLO. The blobs in the diagrams denote the higher order QCD corrections, including both virtual and real emission contributions.
  • Figure 4: Feynman diagrams of the real emission corrections to s-channel single top quark production.
  • Figure 5: Feynman diagrams of the real emission corrections to the t-channel single top quark production
  • ...and 4 more figures