Abstract: A search is conducted for new resonances decaying into a W or Z boson and a 125 GeV Higgs boson in the nu(nu) over barb (b) over bar, l(+/-)nu b (b) over bar, and l(+)l(-)b (b) over bar final states, where l(+/-) = e(+/-) or mu(+/-), in pp collisions at root s = 13 TeV. The data used correspond to a total integrated luminosity of 36.1 fb(-1) collected with the ATLAS detector at the Large Hadron Collider during the 2015 and 2016 data-taking periods. The search is conducted by examining the reconstructed invariant or transverse mass distributions of Wh and Zh candidates for evidence of a localised excess in the mass range of 220 GeV up to 5 TeV. No significant excess is observed and the results are interpreted in terms of constraints on the production cross-section times branching fraction of heavy W' and Z' resonances in heavy-vector-triplet models and the CP-odd scalar boson A in two-Higgs-doublet models. Upper limits are placed at the 95% confidence level and range between 9.0 x 10(-4) pb and 7.3 x 10(-1) pb depending on the model and mass of the resonance.

Abstract: A search is presented for photonic signatures, motivated by generalized models of gauge-mediated supersymmetry breaking. This search makes use of proton-proton collision data at root s = 13 TeV corresponding to an integrated luminosity of 36.1 fb(-1) recorded by the ATLAS detector at the LHC, and it explores models dominated by both strong and electroweak production of supersymmetric partner states. Experimental signatures incorporating an isolated photon and significant missing transverse momentum are explored. These signatures include events with an additional photon or additional jet activity not associated with any specific underlying quark flavor. No significant excess of events is observed above the Standard Model prediction, and 95% confidence-level upper limits of between 0.083 and 0.32 fb are set on the visible cross section of contributions from physics beyond the Standard Model. These results are interpreted in terms of lower limits on the masses of gluinos, squarks, and gauginos in the context of generalized models of gauge-mediated supersymmetry, which reach as high as 2.3 TeV for strongly produced and 1.3 TeV for weakly produced supersymmetric partner pairs.

Abstract: A search for the narrow structure, X(5568), reported by the DO Collaboration in the decay sequence X -> B-s(0) pi +/-, B-s(0) -> J/psi phi, is presented. The analysis is based on a data sample recorded with the ATLAS detector at the LHC corresponding to 4.9 fb(-1) of pp collisions at 7 TeV and 19.5 fb(-1)at 8 TeV. No significant signal was found. Upper limits on the number of signal events, with properties corresponding to those reported by DO, and on the A production rate relative to B-s(0) mesons, rho x, were determined at 95% confidence level. The results are N(X) < 382 and rho x <0.015 for B-s(0) mesons with transverse momenta above 10 GeV and N(X) < 356 and rho(x) < 0.016 for transverse momenta above 15 GeV. Limits are also set for potential B-s(0) pi(+) resonances in the mass range 5550 to 5700 MeV.

Abstract: A search for the standard model Higgs boson produced in association with a top-quark pair, t(t)overbar H, is presented. The analysis uses 36.1 fb(-1) of pp collision data at root s = 13 TeV collected with the ATLAS detector at the Large Hadron Collider in 2015 and 2016. The search targets the H -> b(b)overbar decay mode. The selected events contain either one or two electrons or muons from the top-quark decays, and are then categorized according to the number of jets and how likely these are to contain b-hadrons. Multivariate techniques are used to discriminate between signal and background events, the latter being dominated by ft + jets production. For a Higgs boson mass of 125 GeV, the ratio of the measured t(t)overbarH signal cross-section to the standard model expectation is found to be μ= 0.84(-0.61)(+0.64). A value of μgreater than 2.0 is excluded at 95% confidence level (C.L.) while the expected upper limit is μ< 1.2 in the absence of a t(t)overbar H signal.

Abstract: A search for the supersymmetric partners of quarks and gluons (squarks and gluinos) in final states containing hadronic jets and missing transverse momentum, but no electrons or muons, is presented. The data used in this search were recorded in 2015 and 2016 by the ATLAS experiment in root s = 13 TeV proton-proton collisions at the Large Hadron Collider, corresponding to an integrated luminosity of 36.1 fb(-1). The results are interpreted in the context of various models where squarks and gluinos are pair produced and the neutralino is the lightest supersymmetric particle. An exclusion limit at the 95% confidence level on the mass of the gluino is set at 2.03 TeV for a simplified model incorporating only a gluino and the lightest neutralino, assuming the lightest neutralino is massless. For a simplified model involving the strong production of mass-degenerate first-and second-generation squarks, squark masses below 1.55 TeVare excluded if the lightest neutralino is massless. These limits substantially extend the region of supersymmetric parameter space previously excluded by searches with the ATLAS detector.