This article presents measurements of tt¯ differential cross-sections in a fiducial phase-space region, using an integrated luminosity of 3.2 fb- 1of proton–proton data at a centre-of-mass energy of s=13 TeV recorded by the ATLAS experiment at the LHC in 2015. Differential cross-sections are measured as a function of the transverse momentum and absolute rapidity of the top quark, and of the transverse momentum, absolute rapidity and invariant mass of the tt¯ system. The tt¯ events are selected by requiring one electron and one muon of opposite electric charge, and at least two jets, one of which must be tagged as containing a b-hadron. The measured differential cross-sections are compared to predictions of next-to-leading order generators matched to parton showers and the measurements are found to be consistent with all models within the experimental uncertainties with the exception of the Powheg-Box+ Herwig++ predictions, which differ significantly from the data in both the transverse momentum of the top quark and the mass of the tt¯ system.

Measurements of top-quark pair differential cross-sections in the eμ channel in pp collisions at √s=13 TeV using the ATLAS detector

Amoroso, S.;Barbero, M.;Bellagamba, L.;IRALA BENITEZ, JULIO CESAR;Bona, M.;Cairo, V. M.;Callea, G.;Cao, T.;Capua, M.;Cardillo, F.;Carli, I.;Cavaliere, V.;Cerri, A.;Chen, H.;Chiarella, V.;Colombo, T.;Conti, G.;Crosetti, G.;David, C.;De Maria, A.;De Pedis, D.;Del Gaudio, M.;DeMarco, D. A.;Fabbri, L.;Farina, C.;Fischer, A.;Francis, D.;Gabrielli, A.;Gabrielli, A.;Glasman, C.;Iacobucci, G.;Iodice, M.;Jackson, B.;La Rotonda, L.;Le, B.;Li, C.;Li, S.;Liu, J.;Liu, L.;Liu, M.;Liu, M.;Liu, Y.;Lu, N.;Madaffari, D.;Mancini, G.;Martinez, M.;Mastroberardino, A.;Melo, M.;Meoni, E.;Merola, L.;