Measurement of jets produced in top quark events using the di-lepton final state with 2 $b$-tagged jets in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector

Measurements of the normalized differential cross-sections of top-quark pair production are presented as a function of multiplicity of additional jets using 3.2 $fb^{-1}$ of pp collision data at a centre-of-mass energy of 13 TeV. The data are corrected to obtain a particle-level fiducial cross-section as a function of jet multiplicity. Events are required to have a pair of oppositely charged leptons and at least two b-jets, all with transverse momentum above 25 GeV. The jet multiplicity for the additional jets is obtained for various jet transverse momentum thresholds: 25, 40, 60 and 80 GeV. The results are compared to predictions of different NLO Monte Carlo models and to variations of initial- and final-state radiation within Powheg+Pythia6 and good agreement is reached overall. Among the different shower variations the settings leading to more radiation describe the data best.