Abstract: This paper presents measurements of the W+->mu+nu and W-->mu-nu cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton-proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2fb(-1). The precision of the cross-section measurements varies between 0.8 and 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.

Abstract: This paper describes a study of techniques for identifying Higgs bosons at high transverse momenta decaying into bottom-quark pairs, H -> b (b) over bar, for proton-proton collision data collected by the ATLAS detector at the Large Hadron Collider at a centre-of-mass energy root s = 13 TeV. These decays are reconstructed from calorimeter jets found with the anti-k(t) R = 1.0 jet algorithm. To tag Higgs bosons, a combination of requirements is used: b-tagging of R = 0.2 track-jets matched to the large-R calorimeter jet, and requirements on the jet mass and other jet substructure variables. The Higgs boson tagging efficiency and corresponding multijet and hadronic top-quark background rejections are evaluated using Monte Carlo simulation. Several benchmark tagging selections are defined for different signal efficiency targets. The modelling of the relevant input distributions used to tag Higgs bosons is studied in 36 fb(-1) of data collected in 2015 and 2016 using g -> b (b) over bar and Z(-> b (b) over bar)gamma event selections in data. Both processes are found to be well modelled within the statistical and systematic uncertainties.

Abstract: The production cross-sections for W +/- and Z bosons are measured using ATLAS data corresponding to an integrated luminosity of 4.0 pb-1 collected at a centre-ofmass energy v s = 2.76 TeV. The decay channels W and Z. are used, where can be an electron or a muon. The cross-sections are presented for a fiducial region defined by the detector acceptance and are also extrapolated to the full phase space for the total inclusive production cross-section. The combined (average) total inclusive cross-sections for the electron and muon channels are: s tot W+ = 2312 +/- 26 (stat.) +/- 27 (syst.) +/- 72 (lumi.) +/- 30 (extr.) pb, s tot W- = 1399 +/- 21 (stat.) +/- 17 (syst.) +/- 43 (lumi.) +/- 21 (extr.) pb, s tot Z. = 323.4 +/- 9.8 (stat.) +/- 5.0 (syst.) +/- 10.0 (lumi.) +/- 5.5(extr.) pb. Measured ratios and asymmetries constructed using these cross-sections are also presented. These observables benefit from full or partial cancellation of many systematic uncertainties that are correlated between the different measurements.

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 t <overline> 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 fb-1. Due to the large tt 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.

Abstract: A measurement of W-+/- boson production in Pb+Pb collisions at root s(NN) = 5.02 TeV is reported using data recorded by the ATLAS experiment at the LHC in 2015, corresponding to a total integrated luminosity of 0.49 nb(-1). The W-+/- bosons are reconstructed in the electron or muon leptonic decay channels. Production yields of leptonically decaying W-+/- bosons, normalised by the total number of minimum-bias events and the nuclear thickness function, are measured within a fiducial region defined by the detector acceptance and the main kinematic requirements. These normalised yields are measured separately for W+ and W- bosons, and are presented as a function of the absolute value of pseudorapidity of the charged lepton and of the collision centrality. The lepton charge asymmetry is also measured as a function of the absolute value of lepton pseudorapidity. In addition, nuclear modification factors are calculated using the W-+/- boson production cross-sections measured in pp collisions. The results are compared with predictions based on next-to-leading-order calculations with CT14 parton distribution functions as well as with predictions obtained with the EPPS16 and nCTEQ15 nuclear parton distribution functions. No dependence of normalised production yields on centrality and a good agreement with predictions are observed for mid-central and central collisions. For peripheral collisions, the data agree with predictions within 1.7 (0.9) standard deviations for W- (W+) bosons.