The PanDA (Production and Distributed Analysis) Workload Management System is used for ATLAS distributed production and analysis worldwide. The needs of ATLAS global computing imposed challenging ...requirements on the design of PanDA in areas such as scalability, robustness, automation, diagnostics, and usability for both production shifters and analysis users. Through a system-wide job database, the PanDA monitor provides a comprehensive and coherent view of the system and job execution, from high level summaries to detailed drill-down job diagnostics. It is (like the rest of PanDA) an Apache-based Python application backed by Oracle. The presentation layer is HTML code generated on the fly in the Python application which is also responsible for managing database queries. However, this approach is lacking in user interface flexibility, simplicity of communication with external systems, and ease of maintenance. A decision was therefore made to migrate the PanDA monitor server to Django Web Application Framework and apply JSON/AJAX technology in the browser front end. This allows us to greatly reduce the amount of application code, separate data preparation from presentation, leverage open source for tools such as authentication and authorization mechanisms, and provide a richer and more dynamic user experience. We describe our approach, design and initial experience with the migration process.
To overcome scalability limitations in database access on the Grid, ATLAS introduced the Database Release technology replicating databases in files. For years Database Release technology assured ...scalable database access for Monte Carlo production on the Grid. Since previous CHEP, Database Release technology was used successfully in ATLAS data reprocessing on the Grid. Frozen Conditions DB snapshot guarantees reproducibility and transactional consistency isolating Grid data processing tasks from continuous conditions updates at the "live" Oracle server. Database Release technology fully satisfies the requirements of ALLAS data reprocessing and Monte Carlo production. We parallelized the Database Release build workflow to avoid linear dependency of the build time on the length of LHC data-taking period. In recent data reprocessing campaigns the build time was reduced by an order of magnitude thanks to a proven master-worker architecture used in the Google MapReduce. We describe further Database Release optimizations scaling up the technology for the LHC long run.
The production of exotic heavy hadronic particles arises in several models for physics beyond the standard model. The focus is on R-hadrons, which are stable hadronized gluinos, predicted by certain ...supersymmetric models. Interactions and signatures of single R-hadrons are studied with the ATLAS simulation and reconstruction framework. The ATLAS fast simulation framework has been extended to include parameterizations for R-hadrons. Based on topological and kinematic variables only, the discovery potential of the ATLAS detector for R-hadron events produced in \(pp\to\tilde{g}\tilde{g}\), is studied for masses below 2 TeV/c2. R-hadrons with masses as predicted by standard SUSY scenarios would be discovered already in the very early stages of the running of the LHC. The discovery reach of heavy gluinos, predicted by for example split supersymmetry models, extends up to at least 1.8 TeV/c2 for three years running of the LHC at low luminosity.
The production system for Grid Data Processing handles petascale ATLAS data reprocessing and Monte Carlo activities. The production system empowered further data processing steps on the Grid ...performed by dozens of ATLAS physics groups with coordinated access to computing resources worldwide, including additional resources sponsored by regional facilities. The system provides knowledge management of configuration parameters for massive data processing tasks, reproducibility of results, scalable database access, orchestrated workflow and performance monitoring, dynamic workload sharing, automated fault tolerance and petascale data integrity control. The system evolves to accommodate a growing number of users and new requirements from our contacts in ATLAS main areas: Trigger, Physics, Data Preparation and Software & Computing. To assure scalability, the next generation production system architecture development is in progress. We report on scaling up the production system for a growing number of users providing data for physics analysis and other ATLAS main activities.
During massive data reprocessing operations an ATLAS Conditions Database application must support concurrent access from numerous ATLAS data processing jobs running on the Grid. By simulating ...realistic work-flow, ATLAS database scalability tests provided feedback for Conditions Db software optimization and allowed precise determination of required distributed database resources. In distributed data processing one must take into account the chaotic nature of Grid computing characterized by peak loads, which can be much higher than average access rates. To validate database performance at peak loads, we tested database scalability at very high concurrent jobs rates. This has been achieved through coordinated database stress tests performed in series of ATLAS reprocessing exercises at the Tier-1 sites. The goal of database stress tests is to detect scalability limits of the hardware deployed at the Tier-1 sites, so that the server overload conditions can be safely avoided in a production environment. Our analysis of server performance under stress tests indicates that Conditions Db data access is limited by the disk I/O throughput. An unacceptable side-effect of the disk I/O saturation is a degradation of the WLCG 3D Services that update Conditions Db data at all ten ATLAS Tier-1 sites using the technology of Oracle Streams. To avoid such bottlenecks we prototyped and tested a novel approach for database peak load avoidance in Grid computing. Our approach is based upon the proven idea of pilot job submission on the Grid: instead of the actual query, an ATLAS utility library sends to the database server a pilot query first.
Advances in the simulation of Transition Radiation Detectors Nevski, Pavel
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2004, Letnik:
522, Številka:
1
Journal Article
Recenzirano
Different techniques used to simulate the behaviour of the Transition Radiation Detectors are discussed.
We report the first observations of the first harmonic (directed flow, v(1)) and the fourth harmonic (v(4)), in the azimuthal distribution of particles with respect to the reaction plane in Au+Au ...collisions at the BNL Relativistic Heavy Ion Collider (RHIC). Both measurements were done taking advantage of the large elliptic flow (v(2)) generated at RHIC. From the correlation of v(2) with v(1) it is determined that v(2) is positive, or in-plane. The integrated v(4) is about a factor of 10 smaller than v(2). For the sixth (v(6)) and eighth (v(8)) harmonics upper limits on the magnitudes are reported.
A new inner vertex detector for STAR Wieman, H.; Bieser, F.; Kleinfelder, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2001, Letnik:
473, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We report on design considerations for a new inner vertex detector for the STAR experiment at RHIC. A brief description of the STAR experiment and motivation for a high resolution vertex detector are ...presented.
The end-cap Transition Radiation Tracker (TRT), consisting of 36 modules (wheels), is being constructed as a part of the ATLAS Inner Detector at the CERN LHC. This paper describes a method for ...determining the wire positions inside the straw proportional tubes (SPT), which are the basic building blocks of the ATLAS TRT, with an accuracy of better than
10
μm
. The procedure involves moving a narrow monochromatic X-ray beam across the straw and measuring the counting rate as a function of the position of the X-ray beam in the straw. To achieve this goal, a Beam Directing Device (BDD), providing the possibility to direct the X-ray beam in a chosen direction within some solid angle and supplying an accurate angular measurement system, has been constructed. The results of the wire position measurements performed using this BDD on a full-scale mechanical prototype end-cap wheel of the TRT are presented in this paper.
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