Top pair production cross sections at LHCb

The production and decay properties of the top-quark are sensitive to new physics in several scenarios beyond the Standard Model. LHCb is the only experiment where the top-quark can be studied in the forward region exploiting, therefore, production mechanisms different from ATLAS and CMS experiments. The first cross section measurement in the forward region has been performed at $\sqrt{s}=7, 8$ TeV. The most precise determination at LHCb uses data collected at $\sqrt{s}=13$ TeV requiring final states with a $b$-jet and two leptons, muon and electron, coming from the $W$ decay. A description of these measurements is provided together with comparison with theories.