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Higher-order corrections for $t{\bar t}Z$ production

Nikolaos Kidonakis, Chris Foster

TL;DR

This work addresses precise theoretical predictions for associated ttZ production in proton collisions by computing higher-order QCD and EW corrections. It employs soft-gluon resummation in 1PI kinematics to derive approximate NNLO and approximate N^3LO cross sections, supplemented by NLO EW corrections, delivering aN^3LO QCD+NLO EW results. The results show large higher-order corrections, with K-factors around 1.5 at LHC energies and substantial enhancements in differential distributions, and they are validated against LHC measurements. The findings improve the precision of the top-Z coupling determination and sharpen constraints on new physics in ttZ production.

Abstract

We present calculations of higher-order QCD and electroweak (EW) corrections to the associated production of a top-antitop quark pair and a $Z$ boson, i.e. $t{\bar t}Z$ production, in proton collisions. We find that the contributions from soft-gluon corrections are numerically dominant and large. We present approximate NNLO (aNNLO) and approximate N$^3$LO (aN$^3$LO) cross sections that include soft corrections on top of the exact NLO QCD result. We also add electroweak corrections through NLO. We compare our aN$^3$LO QCD + NLO EW theoretical results to measurements of total cross sections from the LHC, and we also calculate top-quark differential distributions in transverse momentum and rapidity.

Higher-order corrections for $t{\bar t}Z$ production

TL;DR

This work addresses precise theoretical predictions for associated ttZ production in proton collisions by computing higher-order QCD and EW corrections. It employs soft-gluon resummation in 1PI kinematics to derive approximate NNLO and approximate N^3LO cross sections, supplemented by NLO EW corrections, delivering aN^3LO QCD+NLO EW results. The results show large higher-order corrections, with K-factors around 1.5 at LHC energies and substantial enhancements in differential distributions, and they are validated against LHC measurements. The findings improve the precision of the top-Z coupling determination and sharpen constraints on new physics in ttZ production.

Abstract

We present calculations of higher-order QCD and electroweak (EW) corrections to the associated production of a top-antitop quark pair and a boson, i.e. production, in proton collisions. We find that the contributions from soft-gluon corrections are numerically dominant and large. We present approximate NNLO (aNNLO) and approximate NLO (aNLO) cross sections that include soft corrections on top of the exact NLO QCD result. We also add electroweak corrections through NLO. We compare our aNLO QCD + NLO EW theoretical results to measurements of total cross sections from the LHC, and we also calculate top-quark differential distributions in transverse momentum and rapidity.
Paper Structure (3 sections, 8 equations, 2 figures)

This paper contains 3 sections, 8 equations, 2 figures.

Table of Contents

  1. Introduction
  2. Resummation of soft-gluon corrections for $t{\bar{t}}Z$ production
  3. Total and differential cross sections

Figures (2)

  • Figure 1: The total cross sections for $t{\bar{t}}Z$ production in $pp$ collisions. The left plot shows cross sections at orders from NLO QCD through aN$^3$LO QCD + NLO EW, and the right plot shows a comparison with LHC data at 7, 8, and 13 TeV energies CMSATLAS.
  • Figure 2: The top-quark $p_T$ (left) and rapidity (right) distributions at orders from NLO QCD through aN$^3$LO QCD + NLO EW for $t{\bar{t}}Z$ production in $pp$ collisions at LHC energy of 13.6 TeV.