Abstract
Single- and double-differential cross-section measurements are presented for the production of top-quark pairs, in the lepton + jets channel at particle and parton level. Two topologies, resolved and boosted, are considered and the results are presented as a function of several kinematic variables characterising the top and tbar{t} system and jet multiplicities. The study was performed using data from pp collisions at centre-of-mass energy of 13 TeV collected in 2015 and 2016 by the ATLAS detector at the CERN Large Hadron Collider (LHC), corresponding to an integrated luminosity of 36~mathrm {fb}^{-1}. Due to the large tbar{t} cross-section at the LHC, such measurements allow a detailed study of the properties of top-quark production and decay, enabling precision tests of several Monte Carlo generators and fixed-order Standard Model predictions. Overall, there is good agreement between the theoretical predictions and the data.
Highlights
Background simulation samplesSeveral processes can produce the same final state as the tt +jets channel
The missing transverse momentum ETmiss is defined as the magnitude of the pTmiss vector computed from the negative sum of the transverse momenta of the reconstructed calibrated physics objects together with an additional soft term constructed with all tracks that are associated with the primary vertex but not with these objects [102, 103]
Single- and double-differential cross-sections for the production of top-quark pairs are measured in the +jets channel at particle and parton level, in the resolv√ed and boosted topologies, using data from pp collisions at s = 13 TeV collected in 2015 and 2016 by the ATLAS detector at the CERN Large Hadron Collider and corresponding to an integrated luminosity of 36.1 fb−1
Summary
ATLAS is a multipurpose detector [29] that provides nearly full solid angle coverage around the interaction point. Within the region |η| < 3.2, electromagnetic calorimetry is provided by barrel and endcap high-granularity lead/liquid-argon (LAr) calorimeters, with an additional thin LAr presampler covering |η| < 1.8, to correct for energy loss in material upstream of the calorimeters. The solid angle coverage is completed with forward copper/LAr and tungsten/LAr calorimeter modules optimised for electromagnetic and hadronic measurements respectively. The calorimeters are surrounded by a muon spectrometer within a magnetic field provided by air-core toroid magnets with a bending integral of about 2.5 Tm in the barrel and up to 6 Tm in the endcaps. A hardware-based trigger uses custom-made hardware and coarser-granularity detector data to initially reduce the trigger rate to approximately 100 kHz from the original 40 MHz LHC bunch crossing rate. A software-based high-level trigger, which has access to full detector granularity, is applied to further reduce the event rate to 1 kHz
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