Juan Antonio Aguilar Saavedra

Search for dark matter in events with a hadronically decaying W or Z boson and missing transverse momentum in pp collisions at √s = 8 TeV with the ATLAS detector

A search is presented for dark matter pair production in association with a W or Z boson in pp collisions representing 20.3 fb−1 of integrated luminosity at √ s = 8 TeV using data recorded with the ATLAS detector at the Large Hadron Collider. Events with a hadronic jet with the jet mass consistent with a W or Z boson, and with large missing transverse momentum are analyzed. The data are consistent with the standard model expectations. Limits are set on the mass scale in effective field theories that describe the interaction of dark matter and standard model particles, and on the cross section of Higgs production and decay to invisible particles. In addition, cross section limits on the anomalous production of W or Z bosons with large missing transverse momentum are set in two fiducial regions. ar X iv :1 30 9. 40 17 v2 [ he pex ] 3 0 Ja n 20 14 Search for Dark Matter in Events with a Hadronically Decaying W or Z Boson and Missing Transverse Momentum in pp Collisions at √ s = 8 TeV with the ATLAS Detector

Measurement of the Z/γ* boson transverse momentum distribution in pp collisions at s=7 TeV with the ATLAS detector

A bstractThis paper describes a measurement of the Z/γ* boson transverse momentum spectrum using ATLAS proton-proton collision data at a centre-of-mass energy of s=7

Measurements of normalized differential cross sections for tt¯ production in pp collisions at (s)−−−√=7 TeV using the ATLAS detector

\sqrt{s}=7

Search for supersymmetry in events with large missing transverse momentum, jets, and at least one tau lepton in 20 fb−1 of √s = 8 TeV proton-proton collision data with the ATLAS detector

TeV at the LHC. The measurement is performed in the Z/γ* → e+e− and Z/γ* → μ+μ− channels, using data corresponding to an integrated luminosity of 4.7 fb−1. Normalized differential cross sections as a function of the Z/γ* boson transverse momentum are measured for transverse momenta up to 800 GeV. The measurement is performed inclusively for Z/γ* rapidities up to 2.4, as well as in three rapidity bins. The channel results are combined, compared to perturbative and resummed QCD calculations and used to constrain the parton shower parameters of Monte Carlo generators. This paper describes a measurement of the Z/γ∗ boson transverse momentum spectrum using ATLAS proton–proton collision data at a centre-of-mass energy of √ s = 7 TeV at the LHC. The measurement is performed in the Z/γ∗ → e+e− and Z/γ∗ → μ+μ− channels, using data corresponding to an integrated luminosity of 4.7 fb−1. Normalized differential cross sections as a function of the Z/γ∗ boson transverse momentum are measured for transverse momenta up to 800 GeV. The measurement is performed inclusively for Z/γ∗ rapidities up to 2.4, as well as in three rapidity bins. The channel results are combined, compared to perturbative and resummed QCD calculations and used to constrain the parton shower parameters of Monte Carlo generators. c

Measurements of four-lepton production at the Z resonance in pp collisions at s√=7 and 8 TeV with ATLAS

A search for scalar particles decaying via narrow resonances into two photons in the mass range 65-600 GeV is performed using 20.3  fb(-1) of √s 8 TeV pp collision data collected with the ATLAS detector at the Large Hadron Collider. The recently discovered Higgs boson is treated as a background. No significant evidence for an additional signal is observed. The results are presented as limits at the 95% confidence level on the production cross section of a scalar boson times branching ratio into two photons, in a fiducial volume where the reconstruction efficiency is approximately independent of the event topology. The upper limits set extend over a considerably wider mass range than previous searches.

Search for top squark pair production in final states with one isolated lepton, jets, and missing transverse momentum in √s = 8 TeV pp collisions with the ATLAS detector

Measurements of normalized differential cross-sections for top-quark pair production are presented as a function of the top-quark transverse momentum, and of the mass, transverse momentum, and rapidity of the tt̄ system, in proton–proton collisions at a center-of-mass energy of √ s = 7TeV. The dataset corresponds to an integrated luminosity of 4.6 fb−1, recorded in 2011 with the ATLAS detector at the CERN Large Hadron Collider. Events are selected in the lepton+jets channel, requiring exactly one lepton and at least four jets with at least one of the jets tagged as originating from a b-quark. The measured spectra are corrected for detector efficiency and resolution effects and are compared to several Monte Carlo simulations and theory calculations. The results are in fair agreement with the predictions in a wide kinematic range. Nevertheless, data distributions are softer than predicted for higher values of the mass of the tt̄ system and of the top-quark transverse momentum. The measurements can also discriminate among different sets of parton distribution functions. c

Light Higgs boson discovery from fermion mixing

A search is presented for the production of new heavy quarks that decay to a Z boson and a third-generation Standard Model quark. In the case of a new charge +2/3 quark (T ), the decay targeted is T → Zt, while the decay targeted for a new charge −1/3 quark (B) is B → Zb. The search is performed with a dataset corresponding to 20.3 fb−1 of pp collisions at √ s = 8 TeV recorded in 2012 with the ATLAS detector at the CERN Large Hadron Collider. Selected events contain a high transverse momentum Z boson candidate reconstructed from a pair of oppositely charged same-flavor leptons (electrons or muons), and are analyzed in two channels defined by the absence or presence of a third lepton. Hadronic jets, in particular those with properties consistent with the decay of a b-hadron, are also required to be present in selected events. Different requirements are made on the jet activity in the event in order to enhance the sensitivity to either heavy quark pair production mediated by the strong interaction, or single production mediated by the electroweak interaction. No significant excess of events above the Standard Model expectation is observed, and lower limits are derived on the mass of vector-like T and B quarks under various branching ratio hypotheses, as well as upper limits on the magnitude of electroweak coupling parameters.A bstractA search is presented for the production of new heavy quarks that decay to a Z boson and a third-generation Standard Model quark. In the case of a new charge +2/3 quark (T ), the decay targeted is T → Zt, while the decay targeted for a new charge −1/3 quark (B) is B → Zb. The search is performed with a dataset corresponding to 20.3 fb−1 of pp collisions at s=8