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Gluon induced contributions to WZ and W gamma production at NNLO

K. L. Adamson, D. de Florian, A. Signer

TL;DR

The paper addresses precise predictions for WZ and Wγ production at hadron colliders by including gluon-induced NNLO contributions from gg→WZqq̄ and gg→Wγqq̄, incorporating anomalous triple gauge couplings. It employs an extended subtraction framework (FKS) and helicity amplitudes with W/Z decays in the narrow-width approximation, along with photon isolation to suppress fragmentation. Numerically, the gluon-induced NNLO terms are found to be small due to sign cancellations, with qg and qq̄ channels remaining dominant, and anomalous couplings have only a modest effect on the gg piece. The results imply robust, stable predictions for vector-boson pair production at the LHC and demonstrate the feasibility of incorporating gluon-induced NNLO corrections in precision collider phenomenology.

Abstract

We calculate the contribution of the partonic processes gg->WZ q\bar{q} and gg -> W gamma q\bar{q} to WZ and W gamma pair production at hadron colliders, including anomalous triple gauge-boson couplings. We use the helicity method and include the decay of the W and Z-boson into leptons in the narrow-width approximation. In order to integrate over the q\bar{q} final state phase space we use an extended version of the subtraction method to NNLO and remove collinear singularities explicitly. Due to the large gluon density at low x, the gluon induced terms of vector-boson pair production are expected to be the dominant NNLO QCD correction, relevant at LHC energies. However, we show that due to a cancellation they turn out to provide a rather small contribution, anticipating good stability for the perturbative expansion.

Gluon induced contributions to WZ and W gamma production at NNLO

TL;DR

The paper addresses precise predictions for WZ and Wγ production at hadron colliders by including gluon-induced NNLO contributions from gg→WZqq̄ and gg→Wγqq̄, incorporating anomalous triple gauge couplings. It employs an extended subtraction framework (FKS) and helicity amplitudes with W/Z decays in the narrow-width approximation, along with photon isolation to suppress fragmentation. Numerically, the gluon-induced NNLO terms are found to be small due to sign cancellations, with qg and qq̄ channels remaining dominant, and anomalous couplings have only a modest effect on the gg piece. The results imply robust, stable predictions for vector-boson pair production at the LHC and demonstrate the feasibility of incorporating gluon-induced NNLO corrections in precision collider phenomenology.

Abstract

We calculate the contribution of the partonic processes gg->WZ q\bar{q} and gg -> W gamma q\bar{q} to WZ and W gamma pair production at hadron colliders, including anomalous triple gauge-boson couplings. We use the helicity method and include the decay of the W and Z-boson into leptons in the narrow-width approximation. In order to integrate over the q\bar{q} final state phase space we use an extended version of the subtraction method to NNLO and remove collinear singularities explicitly. Due to the large gluon density at low x, the gluon induced terms of vector-boson pair production are expected to be the dominant NNLO QCD correction, relevant at LHC energies. However, we show that due to a cancellation they turn out to provide a rather small contribution, anticipating good stability for the perturbative expansion.

Paper Structure

This paper contains 4 sections, 16 equations, 5 figures.

Table of Contents

  1. Introduction
  2. Calculation
  3. Numerical Results
  4. Conclusions

Figures (5)

  • Figure 1: Partonic cross sections for $W\gamma$: $\hat{\sigma}_{q\bar{q}}$, $\hat{\sigma}_{qg}$ and $\hat{\sigma}_{gg}$.
  • Figure 2: Partonic cross sections for $WZ$: $\hat{\sigma}_{q\bar{q}}$, $\hat{\sigma}_{qg}$ and $\hat{\sigma}_{gg}$
  • Figure 3: $W\gamma$ production: $p_T$ distribution for LHC, $q\bar{q}, qg$ and $gg$ pieces separately
  • Figure 4: $WZ$ production: $p_T$ distribution for LHC, $q\bar{q}, qg$ and $gg$ pieces separately
  • Figure 5: Partonic cross section $\hat{\sigma}_{q\bar{q}}$, $\hat{\sigma}_{qg}$ and $\hat{\sigma}_{gg}$ for $WZ$ production with anomalous couplings as given in eq. (\ref{['anom_couplings']})