A search for undiscovered particles decaying into top-antitop quark pairs produced in proton-proton collisions with the ATLAS experiment at the Large Hadron Collider utilizing 20.3 fb$^-1$ of data collected at $\sqrt{s}=8$ \tev\ center-of-mass energy during the 2012 data taking period is presented. The invariant mass spectrum of events containing multiple jets, exactly one lepton, and missing transverse energy and which are consistent with the decay of a top-antitop quark pair is studied and found to be consistent with that predicted by the Standard Model. Upper limits on the production cross section times branching ratio of several benchmark signal models are set at a 95\% confidence level.

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Supersymmetry is at an exciting stage of development. It extends the Standard Model of particle physics into a more powerful theory that both explains more and allows more questions to be addressed. Most important, it opens a window for studying and testing fundamental theories at the Planck scale. Experimentally we are finally entering the intensity and energy regions where superpartners are likely to be detected, and then studied. There has been progress in understanding the remarkable physics implications of supersymmetry, including the derivation of the Higgs mechanism, the unification of the Standard Model forces, cosmological connections such as a candidate for the cold dark matter of the universe and the scalar fields that drive inflation and their potential, the relationship to Planck scale theories, and more.While there are a number of reviews and books where the mathematical structure and uses of supersymmetry can be learned, there are few where the particle physics is the main focus. This book fills that gap. It begins with an excellent pedagogical introduction to the physics and methods and formalism of supersymmetry, by S Martin, which is accessible to anyone with a basic knowledge of the Standard Model of particle physics. Next is an overview of open questions by K Dienes and C Kolda, followed by chapters on topics ranging from how to detect superpartners to connections with Planck scale theories, by leading experts.This invaluable book will allow any interested physicist to understand the coming experimental and theoretical progress in supersymmetry, and will also help students and workers to quickly learn new aspects of supersymmetry they want to pursue.

Abstract: The start of the Large Hadron Collider provides an unprecedent opportunity for the exploration of physics at the TeV scale. It is expected to perform precise tests of the structure of the Standard Model and to hint at the structure of the physical laws at a more fundamental level. The first part of this work describes a tune of the initial- and final- state radiation parameters in the Pythia8 Monte Carlo generator, using ATLAS measurements of ttbar production at 7 TeV. The results are compared to previous tunes to the Z boson transverse momentum at the LHC, and to the LEP event shapes in Z boson hadronic decays, testing of the universality of the parton shower model. The tune of Pythia8 to the ttbar measurements is applied to the next-to-leading or- der generators MadGraph5_aMC@NLO and Powheg, and additional parameters of these generators are tuned to the ttbar data. For the first time in the context of Monte Carlo tuning, the correlation of the experimental uncertainties has been used to constrain the parameters of the Monte Carlo models. In the second section we report results of a model independent search for new phenomena with data recorded by the ATLAS detector at 8 TeV. Event topologies involving isolated electrons, photons, muons, jets, b-jets and missing transverse momentum are investigated. The events are subdivided according to their final states into 697 exclusive analysis channels. For each channel, a search algorithm tests the compatibility of the effective mass distribution in data against the distribution in the Monte Carlo simulated background. No significant deviations between data and the Standard Model expectations have been observed

This volume stresses the important physics developments at various collider facilities. Details of detector systems and their special features for exploiting the strength of a particular collider are also emphasized. The theoretical studies pursue the limits of the standard model and explore the new physics that may emerge at high energy facilities. The lectures are of a pedagogical nature, so that they are useful to students and post-doctoral fellows.

A collection of lectures from eight authoritative speakers, High Energy Phenomenology is a concise introduction for postgraduates new to the field and provides a comprehensive overview of important research activities, results, and future directions for existing researchers. Coverage includes Ian Aitchison's introduction of standard model foundations, HERA physics, the physics and experimental challenges of future hadron colliders, and particle physics and cosmology. The book concludes with Alain Blondel's chapter on precision tests of the standard electroweak model at LEP.