[en] The ATLAS computing model describes a hierarchical distributed virtual computing facility within which are defined Tier-1 and Tier-2 computing centres having certain specific MOU agreed roles and capacities to be used for the benefit and at the direction of ATLAS as a whole. In this model the primary functions of the Tier-1 are to host and provide long term storage for, access to and re-reconstruction of a subset of the ATLAS RAW data (20% in the case of the Tier-1), provide access to ESD, AOD and TAG data sets and support the analysis of these data sets. The primary functions of the Tier-2.s are simulation (they provide the bulk of simulation for ATLAS), calibration, chaotic analysis for a subset of analysis groups and hosting of AOD, TAG and some physics group samples. Tier-3 sites are institution-level non-ATLAS funded or controlled centres/clusters which wish to participate in ATLAS computing, presumably most frequently in support of the particular interests of local physicists (physicists at the local Tier-3 decide how these resources are used). These are clusters of computers which can vary widely in size. It should be noted that substantial institutional funding to originate such clusters is potentially available, and that they could make a real contribution to the impact of ATLAS on the overall ATLAS physics output. As such, there is considerable value in providing some level of technical support to these sites. In this talk the experience gained on running, maintaining, supporting and managing a Tier2 centre will be presented. Finally, a Tier-3 prototype at IFIC-Valencia is going to be discussed, in order to meet ATLAS data-taking requirements. (Author)

[en] ATLAS project has been asked to define the scope and role of Tier-3 resources (facilities or centres) within the existing ATLAS computing model, activities and facilities. This document attempts to address these questions by describing Tier-3 resources generally, and their relationship to the ATLAS Software and Computing Project. Originally the tiered computing model came out of MONARC (see http://monarc.web.cern.ch/MONARC/) work and was predicated upon the network being a scarce resource. In this model the tiered hierarchy ranged from the Tier-0 (CERN) down to the desktop or workstation (Tier 3). The focus on defining the roles of each tiered component has evolved with the initial emphasis on the Tier-0 (CERN) and Tier-1 (National centres) definition and roles. The various LHC projects, including ATLAS, then evolved the tiered hierarchy to include Tier-2s (Regional centers) as part of their projects. Tier-3s, on the other hand, have (implicitly and sometime explicitly) been defined as whatever an institution could construct to support their Physics goals using institutional and otherwise leveraged resources and therefore have not been considered to be part of the official ATLAS Research Program computing resources nor under their control, meaning there is no formal MOU process to designate sites as Tier-3s and no formal control of the program over the Tier-3 resources. Tier-3s are the responsibility of individual institutions to define, fund, deploy and support. However, having noted this, we must also recognize that Tier-3s must exist and will have implications for how our computing model should support ATLAS physicists. Tier-3 users will want to access data and simulations and will want to enable their Tier-3 resources to support their analysis and simulation work. Tiers 3s are an important resource for physicists to analyze LHC (Large Hadron Collider) data. This document will define how Tier-3s should best interact with the ATLAS computing model, detail the conditions under which Tier-3s can expect some level of support and set reasonable expectations for the scope and support of ATLAS Tier-3 sites. (Author)

[en] The ATLAS detector will explore the high-energy frontier of Particle Physics collecting the proton-proton collisions delivered by the LHC (Large Hadron Collider). Starting in spring 2008, the LHC will produce more than 10 Peta bytes of data per year. The adapted tiered hierarchy for computing model at the LHC is: Tier-0 (CERN), Tiers-1 and Tiers-2 centres distributed around the word. The ATLAS Distributed Analysis (DA) system has the goal of enabling physicists to perform Grid-based analysis on distributed data using distributed computing resources. IFIC Tier-2 facility is participating in several aspects of DA. In support of the ATLAS DA activities a prototype is being tested, deployed and integrated. The analysis data processing applications are based on the Athena framework. GANGA, developed by LHCb and ATLAS experiments, allows simple switching between testing on a local batch system and large-scale processing on the Grid, hiding Grid complexities. GANGA deals with providing physicists an integrated environment for job preparation, bookkeeping and archiving, job splitting and merging. The experience with the deployment, configuration and operation of the DA prototype will be presented. Experiences gained of using DA system and GANGA in the Top physics analysis will be described. (Author)

[en] In the ATLAS computing model the tiered hierarchy ranged from the Tier-0 (CERN) down to desktops or workstations (Tier-3). The focus on defining the roles of each tiered component has evolved with the initial emphasis on the Tier-0 and Tier-1 definition and roles. The various LHC (Large Hadron Collider) projects, including ATLAS, then evolved the tiered hierarchy to include Tier-2's (Regional centers) as part of their projects. Tier-3 centres, on the other hand, have been defined as whatever an institution could construct to support their Physics goals using institutional and otherwise leveraged resources and therefore have not been considered to be part of the official ATLAS computing resources. However, Tier-3 centres are going to exist and will have implications on how the computing model should support ATLAS physicists. Tier-3 users will want to access LHC data and simulations and will want to enable their resources to support their analysis and simulation work. This document will define how IFIC (Instituto de Fisica Corpuscular de Valencia), after discussing with the ATLAS Tier-3 task force, should interact with the ATLAS computing model, detail the conditions under which Tier-3 centres can expect some level of support and set reasonable expectations for the scope and support of ATLAS Tier-3 sites. (orig.)

[en] The lateral and longitudinal profiles of hadronic showers detected by a prototype of the ATLAS Iron-Scintillator Tile Hadron Calorimeter have been investigated. This calorimeter presents a unique longitudinal configuration of scintillator tiles. Using a fine-grained pion beam scan at 100 GeV, a detailed picture of transverse shower behaviour is obtained. The underlying radial energy densities for the four depth segments and for the entire calorimeter have been reconstructed. A three-dimensional hadronic shower parametrisation has been developed. The results presented here are useful for understanding the performance of iron-scintillator calorimeters, for developing fast simulations of hadronic showers, for many calorimetry problems requiring the integration of a shower energy deposition in a volume and for future calorimeters design