NLO effects in EFT fits to W+W− production at the LHC

Julien Baglio,Ian M Lewis,Sally Dawson

doi:10.1103/physrevd.99.035029

Abstract

We study the impact of anomalous gauge boson and fermion couplings on the production of $W^+W^-$ pairs at potential future LHC upgrades and estimate the sensitivity at $\sqrt{S}=14$ TeV with $3~ab^{-1}$ and $\sqrt{S}=27$ TeV with $15~ab^{-1}$. A general technique for including NLO QCD effects in effective field theory (EFT) fits to kinematic distributions is presented, and numerical results are given for $\sqrt{S}=13$ TeV $W^+W^-$ production. Our method allows fits to anomalous couplings at NLO accuracy in any EFT basis and has been implemented in a publicly available version of the POWHEG-BOX. Analytic expressions for the $K$-factors relevant for $13$ TeV total cross sections are given for the HISZ and Warsaw EFT bases and differential $K$-factors can be obtained using the supplemental material. Our study demonstrates the necessity of including anomalous $Z$- fermion couplings in the extraction of limits on anomalous 3-gauge-boson couplings.

Highlights

With the discovery of the Higgs boson, and subsequent measurements of its properties at the LHC, the general features of the Standard Model (SM) electroweak theory have been confirmed experimentally [1]
II B, we present a general method for deriving next-to-leading order (NLO) expressions for the total cross section and for distributions in a SMEFT in terms of a fixed number of subamplitudes, which we term “primitive cross sections.”
To order OðΛ−2nÞ the primed primitive cross sections dσ0ðn; R⃗ i0Þ are defined with the vector R⃗ i evaluated relative to the new basis C⃗ 0: dσ0ðn; R⃗ iÞ ≡ dσnðC⃗ 0 1⁄4 R⃗ iÞ: ð14Þ

Summary

INTRODUCTION

With the discovery of the Higgs boson, and subsequent measurements of its properties at the LHC, the general features of the Standard Model (SM) electroweak theory have been confirmed experimentally [1]. The longitudinally polarized contributions to WþW− grow with energy faster than the SM contributions in the presence of BSM physics This implies that the LHC can put strong constraints on the coefficients of the dimension-6 SMEFT operators. At dimension-8, there are many other possible operators, modifying the triple-gauge-boson interactions and new four-point ggWþW− interactions [16] These operators contribute at tree level at order Oð1=Λ4Þ in the EFT and must be included in a study of the dimension-8 Lagrangian. The effects of anomalous three-gauge-boson couplings exist in the POWHEG-BOX framework [28,29], and we add the additional contributions from anomalous fermion couplings This public tool can be found at [30] and can be used to perform fits to anomalous couplings including NLO QCD and showering effects. EÆμ∓ννat 13 TeV as an illustration of our technique, along with analytic results for the total cross section, as functions of arbitrary EFT coefficients

Effective gauge and fermion interactions

Primitive cross sections

FUTURE PROJECTIONS

Lδ2sys

Findings

CONCLUSIONS