Measurement of jet activity produced in top-quark events with an electron, a muon and two b-tagged jets in the final state in pp collisions at s√=13 TeV with the ATLAS detector

Abstract

Measurements of jet activity in top-quark pair events produced in proton?proton collisionsare presented, using 3.2 fb −1 of pp collision data at a centre-of-mass energy of 13 TeV collec-ted by the ATLAS experiment at the Large Hadron Collider. Events are chosen by requiringan opposite-charge eμ pair and two b-tagged jets in the final state. The normalised differen-tial cross-sections of top-quark pair production are presented as functions of additional-jetmultiplicity and transverse momentum, p T . The fraction of signal events that do not containadditional jet activity in a given rapidity region, the gap fraction, is measured as a function ofthe p T threshold for additional jets, and is also presented for different invariant mass regionsof the eμbb̄ system. All measurements are corrected for detector effects and presented asparticle-level distributions compared to predictions with different theoretical approaches forQCD radiation. While the kinematics of the jets from top-quark decays are described well,the generators show differing levels of agreement with the measurements of observables thatdepend on the production of additional jets.