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Abstract:

A measurement is presented of the inclusive cross-section for b-jet production in association with a Z boson in pp collisions at a centre-of-mass energy of s=7 TeV. The analysis uses the data sample collected by the ATLAS experiment in 2010, corresponding to an integrated luminosity of approximately 36 pb-1. The event selection requires a Z boson decaying into high pT electrons or muons, and at least one b-jet, identified by its displaced vertex, with transverse momentum pT>25 GeV and rapidity |y|<2.1. After subtraction of background processes, the yield is extracted from the vertex mass distribution of the candidate b-jets. The ratio of this cross-section to the inclusive Z cross-section (the average number of b-jets per Z event) is also measured. Both results are found to be in good agreement with perturbative QCD predictions at next-to-leading order. © 2011 CERN.

Abstract:

A search for a narrow Higgs boson resonance in the diphoton mass spectrum is presented based on data corresponding to 7.0fb-1 of integrated luminosity from pp̄ collisions at √s=1.96TeV collected by the CDF experiment. No evidence of such a resonance is observed, and upper limits are set on the cross section times branching ratio of the resonant state as a function of Higgs boson mass. The limits are interpreted in the context of the standard model and one fermiophobic benchmark model where the data exclude fermiophobic Higgs bosons with masses below 114GeV/c2 at a 95% Bayesian credibility level. © 2012 American Physical Society.

Abstract:

The volume and diversity of metadata in an experiment of the size and scope of ATLAS are considerable. Even the definition of metadata may seem context-dependent: data that are primary for one purpose may be metadata for another. ATLAS metadata services must integrate and federate information from inhomogeneous sources and repositories, map metadata about logical or physics constructs to deployment and production constructs, provide a means to associate metadata at one level of granularity with processing or decision-making at another, offer a coherent and integrated view to physicists, and support both human use and programmatic access. In this paper we consider ATLAS metadata, metadata services, and metadata flow principally from the illustrative perspective of how disparate metadata are made available to executing jobs and, conversely, how metadata generated by such jobs are returned. We describe how metadata are read, how metadata are cached, and how metadata generated by jobs and the tasks of which they are a part are communicated, associated with data products, and preserved. We also discuss the principles that guide decision-making about metadata storage, replication, and access..

Abstract:

The ATLAS inner detector is used to reconstruct secondary vertices due to hadronic interactions of primary collision products, so probing the location and amount of material in the inner region of ATLAS. Data collected in 7 TeV pp collisions at the LHC, with a minimum bias trigger, are used for comparisons with simulated events. The reconstructed secondary vertices have spatial resolutions ranging from ∼ 200μm to 1 mm. The overall material description in the simulation is validated to within an experimental uncertainty of about 7%. This will lead to a better understanding of the reconstruction of various objects such as tracks, leptons, jets, and missing transverse momentum. © 2012 CERN.

Abstract:

The ATLAS Metadata Interface ("AMI") was designed as a generic cataloguing system, and as such it has found many uses in the experiment including software release management, tracking of reconstructed event sizes and control of dataset nomenclature. The primary use of AMI is to provide a catalogue of datasets (file collections) which is searchable using physics criteria. In this paper we discuss the various mechanisms used for filling the AMI dataset and file catalogues. By correlating information from different sources we can derive aggregate information which is important for physics analysis; for example the total number of events contained in dataset, and possible reasons for missing events such as a lost file. Finally we will describe some specialized interfaces which were developed for the Data Preparation coordinators. These interfaces manipulate information from both the dataset domain held in AMI, and the run-indexed information held in the ATLAS COMA application (Conditions and Configuration MetadatA)..