Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Single-top $t$-channel production with off-shell and non-resonant effects

A. S. Papanastasiou, R. Frederix, S. Frixione, V. Hirschi, F. Maltoni

TL;DR

This work delivers a first full NLO QCD calculation of electroweak t-channel single-top production with off-shell top quarks, using the complex-mass scheme within aMC@NLO to retain resonant, non-resonant, and interference effects. By comparing to the NWA and an effective theory approach, the study shows that inclusive observables are only mildly affected by finite-width effects, while observables sensitive to the reconstructed top, such as the invariant mass M(W^+,J_b), exhibit substantial deviations. The results reveal that the ET approximation tracks the full off-shell predictions well across many distributions, whereas the NWA can be dramatically inaccurate in regions influenced by off-shell dynamics. These findings underscore the importance of finite-width and interference effects in precision top-quark phenomenology and motivate further work on parton showers and mass extraction systematics.

Abstract

This letter details and discusses the next-to-leading order QCD corrections to $t$-channel electro-weak $W^+ b j$ production, where finite top-width effects are consistently taken into account. The computation is done within the aMC@NLO framework and includes both resonant and non-resonant contributions as well as interferences between the two. Results are presented for the LHC and compared to those of the narrow-width approximation and effective theory approaches.

Single-top $t$-channel production with off-shell and non-resonant effects

TL;DR

This work delivers a first full NLO QCD calculation of electroweak t-channel single-top production with off-shell top quarks, using the complex-mass scheme within aMC@NLO to retain resonant, non-resonant, and interference effects. By comparing to the NWA and an effective theory approach, the study shows that inclusive observables are only mildly affected by finite-width effects, while observables sensitive to the reconstructed top, such as the invariant mass M(W^+,J_b), exhibit substantial deviations. The results reveal that the ET approximation tracks the full off-shell predictions well across many distributions, whereas the NWA can be dramatically inaccurate in regions influenced by off-shell dynamics. These findings underscore the importance of finite-width and interference effects in precision top-quark phenomenology and motivate further work on parton showers and mass extraction systematics.

Abstract

This letter details and discusses the next-to-leading order QCD corrections to -channel electro-weak production, where finite top-width effects are consistently taken into account. The computation is done within the aMC@NLO framework and includes both resonant and non-resonant contributions as well as interferences between the two. Results are presented for the LHC and compared to those of the narrow-width approximation and effective theory approaches.

Paper Structure

This paper contains 5 sections, 3 equations, 6 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Unstable single-top production
  3. Process definition
  4. Results
  5. Conclusions

Figures (6)

  • Figure 1: Selection of LO $t$-channel diagrams for EW $W^+ b j$ production in the 5F scheme: resonant (a) and non-resonant (b) & (c).
  • Figure 2: Selection of NLO virtual $t$-channel diagrams for EW $W^+ b j$ production in the 5F scheme: resonant (a) and non-resonant (b) & (c).
  • Figure 3: Selection of LO $s$-channel diagrams for EW $W^+ b j$ production: resonant (a) and non-resonant (b) & (c). These are not included in our calculation.
  • Figure 4: Transverse momentum of light jet, $p_T(J_{\text{light}})$.
  • Figure 5: Invariant mass distribution for the reconstructed top quark, $M(W^+,J_b)$.
  • ...and 1 more figures