ATLAS

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 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)..

Abstract:

Using data corresponding to 4.6-4.7 fb-1 of integrated luminosity from s = 7 TeV pp collisions at the LHC, the ATLAS Collaboration has measured the production cross section of heavy dibosons (WW, WZ, and ZZ) in the fully leptonic decay channels. A first measurement of ZZ production at s = 8 TeV with data corresponding to 5.8 fb-1 of integrated luminosity has also been performed. Differential cross sections are measured for WZ production, and limits are set on anomalous WWZ and WW? couplings.

Abstract:

The ATLAS detector at the LHC is used to search for high-mass states, such as heavy charged gauge bosons (Wʹ), decaying to a charged lepton (electron or muon) and a neutrino. Results are presented based on the analysis of pp collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 4.7 fb−1. No excess beyond Standard Model expectations is observed. AWʹ with Sequential Standard Model couplings is excluded at the 95% credibility level for masses up to 2.55 TeV. Excited chiral bosons (W*) with equivalent coupling strength are excluded for masses up to 2.42 TeV.

Abstract:

Measurements from the CMS experiment at the LHC of dihadron correlations for charged particles produced in PbPb collisions at a nucleon-nucleon centre-of-mass energy of 2. 76 TeV are presented. The results are reported as a function of the particle transverse momenta (pT) and collision centrality over a broad range in relative pseudorapidity (Δη) and the full range of relative azimuthal angle (Δφ). The observed two-dimensional correlation structure in Δη and Δφ is characterised by a narrow peak at (Δη,Δφ)≈(0,0) from jet-like correlations and a long-range structure that persists up to at least {pipe}Δη{pipe}=4. An enhancement of the magnitude of the short-range jet peak is observed with increasing centrality, especially for particles of pT around 1-2 GeV/c. The long-range azimuthal dihadron correlations are extensively studied using a Fourier decomposition analysis. The extracted Fourier coefficients are found to factorise into a product of single-particle azimuthal anisotropies up to pT≈3-3. 5 GeV/c for at least one particle from each pair, except for the second-order harmonics in the most central PbPb events. Various orders of the single-particle azimuthal anisotropy harmonics are extracted for associated particle pT of 1-3 GeV/c, as a function of the trigger particle pT up to 20 GeV/c and over the full centrality range. © 2012 CERN for the benefit of the CMS collaboration.