Hadronic production of top-quark pairs in association with a pair of leptons in the POWHEG BOX framework

Understand

We present an implementation of $t\bar t \ell^+\ell^-$ ($\ell=e,\mu$) hadronic production at next-to-leading order in QCD matched to parton-shower event generators in the POWHEG BOX framework.

• The program we developed includes all leading-order contributions of order $\alpha_s^2\alpha^2$ for the specified final state, as well as the corresponding first-order QCD corrections.
• Decays of the top quarks have been simulated retaining spin-correlations in all tree-level matrix elements.
• We consider the case of the Large Hadron Collider at $\sqrt{s}=13$ TeV and compare results for $t\bar t \ell^+\ell^-$ production in the fiducial volume where the invariant mass of the lepton pairs is centered around the $Z$-boson mass to corresponding predictions for $t\bar{t}Z$ on-shell production with $Z\rightarrow \ell^+\ell^-$.