Abstract: The production of a Z boson in association with a J/psi meson in proton-proton collisions probes the production mechanisms of quarkonium and heavy flavour in association with vector bosons, and allows studies of multiple parton scattering. Using 20.3 fb(-1) of data collected with theATLAS experiment at the LHC in pp collisions at root s = 8 TeV, the first measurement of associated Z + J/psi production is presented for both prompt and non-prompt J/psi production, with both signatures having a significance in excess of 5 sigma. The inclusive production cross-sections for Z boson production (analysed in mu(+) mu(-) or e(+) e(-) decay modes) in association with prompt and non-prompt J/psi (-> mu(+) mu(-)) are measured relative to the inclusive production rate of Z bosons in the same fiducial volume to be (36.8 +/- 6.7 +/- 2.5) x 10(-7) and (65.8 +/- 9.2 +/- 4.2) x 10(-7) respectively. Normalised differential production cross-section ratios are also determined as a function of the J/psi transverse momentum. The fraction of signal events arising from single and double parton scattering is estimated, and a lower limit of 5.3 (3.7) mb at 68 (95)% confidence level is placed on the effective cross-section regulating double parton interactions.

Abstract: A search is presented for the direct pair production of a chargino and a neutralino pp -> (X) over tilde (+/-)(1)(X) over tilde (0)(2), where the chargino decays to the lightest neutralino and the W boson, (X) over tilde (+/-)(1) -> (X) over tilde (0)(1) (W-+/- -> l(+/-)nu), while the neutralino decays to the lightest neutralino and the 125 GeV Higgs boson, (X) over tilde (0)(2) -> (X) over tilde (0)(1) (h -> bb/gamma gamma/l(+/-)nu qq). The final states considered for the search have large missing transverse momentum, an isolated electron or muon, and one of the following: either two jets identified as originating from bottom quarks, or two photons, or a second electron or muon with the same electric charge. The analysis is based on 20.3 fb(-1) of root s = 8 TeV proton-proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with the Standard Model expectations, and limits are set in the context of a simplified supersymmetric model.

Abstract: A search for the Standard Model Higgs boson produced in association with a top-quark pair, , is presented. The analysis uses 20.3 fb(-1) of pp collision data at , collected with the ATLAS detector at the Large Hadron Collider during 2012. The search is designed for the decay mode and uses events containing one or two electrons or muons. In order to improve the sensitivity of the search, events are categorised according to their jet and b-tagged jet multiplicities. A neural network is used to discriminate between signal and background events, the latter being dominated by +jets production. In the single-lepton channel, variables calculated using a matrix element method are included as inputs to the neural network to improve discrimination of the irreducible background. No significant excess of events above the background expectation is found and an observed (expected) limit of 3.4 (2.2) times the Standard Model cross section is obtained at 95 % confidence level. The ratio of the measured signal cross section to the Standard Model expectation is found to be assuming a Higgs boson mass of 125 Gev.

Abstract: Asearch for heavy long-lived multi-charged particles is performed using the ATLAS detector at the LHC. Data collected in 2012 at root s = 8TeV from pp collisions corresponding to an integrated luminosity of 20.3 fb(-1) are examined. Particles producing anomalously high ionisation, consistent with long-livedmassive particleswith electric charges from vertical bar q vertical bar = 2e to vertical bar q vertical bar = 6e are searched for. No signal candidate events are observed, and 95% confidence level crosssection upper limits are interpreted as lower mass limits for a Drell-Yan production model. The mass limits range between 660 and 785 GeV.

Abstract: Measurements of the ZZ and WW final states in the mass range above the 2m(Z) and 2m(W) thresholds provide a unique opportunity to measure the off-shell coupling strength of the Higgs boson. This paper presents constraints on the off-shell Higgs boson event yields normalised to the Standard Model prediction (signal strength) in the ZZ -> 4l, ZZ -> 2l2 nu and WW -> e nu μnu final states. The result is based on pp collision data collected by the ATLAS experiment at the LHC, corresponding to an integrated luminosity of 20.3 fb(-1) at a collision energy of root s = 8 TeV. Using the CLs method, the observed 95 % confidence level (CL) upper limit on the off-shell signal strength is in the range 5.1-8.6, with an expected range of 6.7-11.0. In each case the range is determined by varying the unknown gg -> ZZ and gg -> WW background K-factor from higher-order quantum chromodynamics corrections between half and twice the value of the known signal K-factor. Assuming the relevant Higgs boson couplings are independent of the energy scale of the Higgs boson production, a combination with the on-shell measurements yields an observed (expected) 95 % CL upper limit on Gamma(H)/Gamma(SM)(H) in the range 4.5-7.5 (6.5-11.2) using the same variations of the background K-factor. Assuming that the unknown gg -> VV background K-factor is equal to the signal K-factor, this translates into an observed (expected) 95 % CL upper limit on the Higgs boson total width of 22.7 (33.0) MeV.