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Vector Boson Pair Production in Hadronic Collisions at Order $α_s$: Lepton Correlations and Anomalous Couplings

L. Dixon, Z. Kunszt, A. Signer

TL;DR

This work delivers a comprehensive NLO QCD framework for vector-boson pair production in hadronic collisions with full lepton decay spin correlations and the capability to incorporate anomalous triple gauge couplings. It combines helicity-amplitude methods, the FKS subtraction scheme, and a flexible Monte Carlo implementation to produce infrared-safe predictions for WW, WZ, and ZZ production at Tevatron and LHC energies. The study shows that standard model predictions are robust for total cross sections but exhibit sizable enhancements in high-$p_T$ regions, where anomalous couplings can produce pronounced deviations, highlighting the pathway to tighter experimental constraints. Overall, the approach enables precise SM tests and sensitive probes of new physics in vector-boson self-interactions, leveraging high-energy data from the LHC.

Abstract

We present cross sections for production of electroweak vector boson pairs, $WW$, $WZ$ and $ZZ$, in $p\bar{p}$ and $pp$ collisions, at next-to-leading order in $α_s$. We treat the leptonic decays of the bosons in the narrow-width approximation, but retain all spin information via decay angle correlations. We also include the effects of $WWZ$ and $WWγ$ anomalous couplings.

Vector Boson Pair Production in Hadronic Collisions at Order $α_s$: Lepton Correlations and Anomalous Couplings

TL;DR

This work delivers a comprehensive NLO QCD framework for vector-boson pair production in hadronic collisions with full lepton decay spin correlations and the capability to incorporate anomalous triple gauge couplings. It combines helicity-amplitude methods, the FKS subtraction scheme, and a flexible Monte Carlo implementation to produce infrared-safe predictions for WW, WZ, and ZZ production at Tevatron and LHC energies. The study shows that standard model predictions are robust for total cross sections but exhibit sizable enhancements in high- regions, where anomalous couplings can produce pronounced deviations, highlighting the pathway to tighter experimental constraints. Overall, the approach enables precise SM tests and sensitive probes of new physics in vector-boson self-interactions, leveraging high-energy data from the LHC.

Abstract

We present cross sections for production of electroweak vector boson pairs, , and , in and collisions, at next-to-leading order in . We treat the leptonic decays of the bosons in the narrow-width approximation, but retain all spin information via decay angle correlations. We also include the effects of and anomalous couplings.

Paper Structure

This paper contains 12 sections, 17 equations, 8 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Computation
  3. Standard Model Results
  4. Total Cross Sections
  5. $W^+ W^-$
  6. $W^\pm Z$
  7. Anomalous $W^+W^-Z$ and $W^+W^-\gamma$ Couplings
  8. Triple Gauge Boson Vertices
  9. Tree, Virtual and Bremsstrahlung Amplitudes for $WW$
  10. Tree, Virtual and Bremsstrahlung Amplitudes for $WZ$
  11. Numerical Results
  12. Conclusions

Figures (8)

  • Figure 1: Scale dependence of $\sigma^{\rm cut}$, the cross section for $W$-pair production at the Tevatron with standard cuts. The scale is given in units of $M_W$. We show the LO, NLO and NLO with jet veto curves. The inset shows the three curves normalized to 1 at $\mu = M_W$.
  • Figure 2: Scale dependence of $\sigma^{\rm cut}$, the cross section for $W$-pair production at the LHC with standard cuts. The scale is given in units of $\mu_{\rm st}$ as defined in eq. (\ref{['must']}). We show the LO, NLO and NLO with jet veto curves without additional cuts (left) and with an additional cut $p_T^{\rm max}(\ell)>200$ GeV and $p_T^{\rm min}(\ell)>100$ GeV (right). The insets show the curves normalized to 1 at $\mu=\mu_{\rm st}$.
  • Figure 3: Differential cross sections in pb/GeV for $W^-W^+$ production at the Tevatron for the $p_T$-like variables $p_T(\ell^-)$, $M_{\ell\ell}$, $p_T^{\rm miss}$ and $p_T^{\rm max}$ defined in the text at LO (dashed curves) and NLO (solid curves), with $\mu=M_W$. Standard cuts have been applied and the branching ratios for the leptonic decay of the vector bosons are not included. The insets show the ratio $d\sigma^{NLO}/d\sigma^{LO}$. The units on the horizontal axes are GeV.
  • Figure 4: Differential cross sections in pb for the Tevatron for the $W^-W^+$ angular variables defined in the text at LO (dashed curves) and NLO (solid curves), with $\mu=M_W$. Standard cuts have been applied and the leptonic branching ratios are not included.
  • Figure 5: Differential cross sections in pb/GeV for $W^-W^+$ production at the LHC, for the $p_T$-like variables defined in the text at LO (dashed curves) and NLO (solid curves), with $\mu=M_W$. Standard cuts have been applied and the leptonic branching ratios are not included. Also shown (as dot-dashed lines) are the NLO curves with a jet veto $E_T^{\rm had} < 40$ GeV. The insets show the ratio $d\sigma^{NLO}/d\sigma^{LO}$. The units on the horizontal axes are GeV.
  • ...and 3 more figures