# Associated production of a top quark pair with a heavy electroweak gauge boson at NLO+NNLL accuracy

## TL;DR

This paper performs advanced resummation calculations for top-antitop quark pair production with heavy electroweak bosons at the LHC, significantly improving theoretical predictions and reducing uncertainties, especially for the t-tbar-Z process.

## Contribution

It introduces NNLL resummation of soft gluon corrections for associated top pair and heavy boson production, enhancing accuracy over previous NLO results.

## Key findings

- Resummation increases the t-tbar-Z cross section by nearly 30%.
- Theoretical uncertainties are significantly reduced at NLO+NNLL level.
- Resummation effects are less significant for t-tbar-W processes.

## Abstract

We perform threshold resummation of soft gluon corrections to the total cross sections and the invariant mass distributions for production of a top-antitop quark pair associated with a heavy electroweak boson $V = W^+$, $W^-$ or $Z$ in $pp$ collisions at the Large Hadron Collider. The resummation is carried out at next-to-next-to-leading-logarithmic (NNLL) accuracy using the direct QCD Mellin space technique in the three-particle invariant mass kinematics. It is found that for the $t\bar t Z$ process the soft gluon resummation introduces significant corrections to the next-to-leading order (NLO) results. For the central scale equal to the $t\bar t Z$ invariant mass the corrections reach nearly 30%. For this process, the dominant theoretical uncertainty of the cross section due to the scale choice is significantly reduced at the NLO+NNLL level with respect to the NLO results. The effects of resummation are found to be less pronounced in the $t\bar t W^{\pm}$ case. The obtained results are compared to recent measurements performed by CMS and ATLAS collaborations at the LHC.