HEP computing is approaching the end of an era when simulation parallelization could be performed simply by running one instance of full simulation per core. The increasing number of cores and ...appearance of hardware-thread support both pose a severe limitation on memory and memory-bandwidth available to each execution unit. Typical simulation and reconstruction jobs of AliROOT (offline framework of the ALICE experiment at LHC) do not differ significantly in memory usage - but the input/output rate of reconstruction is approximately three times higher. This makes simulation a more natural candidate for parallelization, especially since the simulation code is relatively stable while the reconstruction code is not expected to settle until the detector is fully calibrated with real data and understood under stable running conditions. We have chosen to use multi-threading solution with one primary particle and all its secondaries being tracked by a given thread. This model corresponds well to Pb-Pb ion collision simulation where 60,000 primary particles need to be transported. After the MC processing of a primary particle is completed, the same thread also performs output serialization. Modifications of ROOT, AliROOT and GEANT3 that were required to perform this task are discussed. Performance of the parallelized version of simulation under varying running conditions is presented.
Do regions matter in ALICE? Widmer, E. D.; Viry, G.; Carminati, F. ...
European physical journal plus,
02/2012, Letnik:
127, Številka:
2
Journal Article
Recenzirano
This study aims at investigating the impact of regional affiliations of centres on the organisation of collaborations within the Distributed Computing ALICE infrastructure, based on social networks ...methods. A self-administered questionnaire was sent to all centre managers about support, email interactions and wished collaborations in the infrastructure. Several additional measures, stemming from technical observations were collected, such as bandwidth, data transfers and Internet Round Trip Time (RTT) were also included. Information for 50 centres were considered (about 70% response rate). Empirical analysis shows that despite the centralisation on CERN, the network is highly organised by regions. The results are discussed in the light of policy and efficiency issues.
An overview is presented of the characteristics of HEP computing and its mapping to the Grid paradigm. This is followed by a synopsis of the main experiences and lessons learned by HEP experiments in ...their use of DataGrid middleware using both the EDG application testbed and the LCG production service. Particular reference is made to experiment ‘data challenges’, and a forward look is given to necessary developments in the framework of the EGEE project.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) The ALICE Collaboration at the LHC has measured the J/ψ and ψ' photoproduction at mid-rapidity in ultra-peripheral Pb-Pb ...collisions at ... The charmonium is identified via its leptonic decay for events where the hadronic activity is required to be minimal. The analysis is based on an event sample corresponding to an integrated luminosity of about 23 mub^sup -1^. The cross section for coherent and incoherent J/ψ production in the rapidity interval -0.9<y<0.9, are ... and ..., respectively. The results are compared to theoretical models for J/ψ production and the coherent cross section is found to be in good agreement with those models incorporating moderate nuclear gluon shadowing at Bjorken-x around 10^sup -3^, such as EPS09 parametrization. In addition the cross section for the process γγarrow righte ^sup +^ e ^sup -^ has been measured and found to be in agreement with models implementing QED at leading order.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A Large Ion Collider Experiment (ALICE) is the dedicated heavy-ion experiment at the CERN LHC and will take data with a bandwidth of up to 1.25 GB/s. It consists of 18 subdetectors that interact with ...five online systems (CTP, DAQ, DCS, ECS, and HLT). Data recorded is read out by DAQ in a raw data stream produced by the subdetectors. In addition the subdetectors produce conditions data derived from the raw data, i.e. calibration and alignment information, which have to be available from the beginning of the reconstruction and therefore cannot be included in the raw data. The extraction of the conditions data is steered by a system called Shuttle. It provides the link between data produced by the subdetectors in the online systems and a dedicated procedure per subdetector, called preprocessor, that runs in the Shuttle system. The preprocessor performs merging, consolidation, and reformatting of the data. Finally, it stores the data in the Grid Offline Conditions DataBase (OCDB) so that they are available for the Offline reconstruction. The reconstruction of a given run is initiated automatically once the raw data is successfully exported to the Grid storage and the run has been processed in the Shuttle framework. These proceedings introduce the Shuttle system. The performance of the system during the ALICE cosmics commissioning and LHC startup is described.
In the metallurgical industries the silica risk has long been known, particularly for the refractoryes maintenance workers. The maintenance of furnaces, ladles and tundisches refractory linings, on ...the current organization of production, is provided by companies under contract. The information available about the characterization of risk for this group of workers are at present inadequate. The study investigates the exposure to dust, also containing free crystalline silica (SLC), through the analysis of samples of commercial products used in the reconstruction of refractory linings of furnaces, ladles and tundisches, materials from the demolition of refractory articles and dust from work areas. It also presents the results of an environmental investigation conducted during the demolition and reconstruction of the refractory in three steel mills. The Authors, by the numerous inspections and the systematic survey of working conditions, have formulated a SLC risk profile and some proposals for prevention.
The iron foundries are still well represented in the area of Brescia and, despite having been involved in a major technological developments, have still risks to the health of workers. In order to ...verify the state of the art and effectiveness of prevention measures implemented by various companies, in recent years have carried out numerous inspections, environmental monitoring and biological. Furthermore, there were in the regional information system diseases reported and/or by the reported health. In particular it is shown that, in addition to chemical and physical risk factors, although in a much reduced compared to the 80s, are still present in our workplace pollutants (PAHs, silica, metal fumes, formaldehyde) at the base of classification of iron foundries in group 1, carcinogenic to humans, IARC, 1987 e 2012.
The directed flow of charged particles at midrapidity is measured in Pb-Pb collisions at sqrts_{NN}=2.76 TeV relative to the collision symmetry plane defined by the spectator nucleons. A negative ...slope of the rapidity-odd directed flow component with approximately 3 times smaller magnitude than found at the highest RHIC energy is observed. This suggests a smaller longitudinal tilt of the initial system and disfavors the strong fireball rotation predicted for the LHC energies. The rapidity-even directed flow component is measured for the first time with spectators and found to be independent of pseudorapidity with a sign change at transverse momenta p_{T} between 1.2 and 1.7 GeV/c. Combined with the observation of a vanishing rapidity-even p_{T} shift along the spectator deflection this is strong evidence for dipolelike initial density fluctuations in the overlap zone of the nuclei. Similar trends in the rapidity-even directed flow and the estimate from two-particle correlations at midrapidity, which is larger by about a factor of 40, indicate a weak correlation between fluctuating participant and spectator symmetry planes. These observations open new possibilities for investigation of the initial conditions in heavy-ion collisions with spectator nucleons.
The ALICE measurement of K_{S}^{0} and Λ production at midrapidity in Pb-Pb collisions at sqrts_{NN}=2.76 TeV is presented. The transverse momentum (p_{T}) spectra are shown for several collision ...centrality intervals and in the p_{T} range from 0.4 GeV/c (0.6 GeV/c for Λ) to 12 GeV/c. The p_{T} dependence of the Λ/K_{S}^{0} ratios exhibits maxima in the vicinity of 3 GeV/c, and the positions of the maxima shift towards higher p_{T} with increasing collision centrality. The magnitude of these maxima increases by almost a factor of three between most peripheral and most central Pb-Pb collisions. This baryon excess at intermediate p_{T} is not observed in pp interactions at sqrts=0.9 TeV and at sqrts=7 TeV. Qualitatively, the baryon enhancement in heavy-ion collisions is expected from radial flow. However, the measured p_{T} spectra above 2 GeV/c progressively decouple from hydrodynamical-model calculations. For higher values of p_{T}, models that incorporate the influence of the medium on the fragmentation and hadronization processes describe qualitatively the p_{T} dependence of the Λ/K_{S}^{0} ratio.
A New Format for Handling Nuclear Data Bak, Sang In; Brun, Rene; Carminati, Federico ...
Journal of the Korean Physical Society,
08/2011, Letnik:
59, Številka:
2(3)
Journal Article
Recenzirano
Odprti dostop
The ASCII ENDF format for nuclear data has been used for four decades. It is practical for human inspection and portability, but it is not very effective for manipulating and displaying the data or ...for using them in Monte-Carlo applications. In this paper we present a prototype of a nuclear data manipulation package (TNudy) based on the ROOT system (http://root.cern.ch). The ROOT object-oriented C++ framework is the de-facto standard in high energy and nuclear physics since ten years. Starting from the ENDF format, the data is stored in machine-portable binary format. Root files also offer a powerful direct access capability to their different sections and compressibility upon writing, minimising the disk occupancy. ROOT offers a complete library of visualisation and mathematical routines and the Virtual Monte-Carlo system, which allows running different transport Monte-Carlo (Geant 4, Geant 3) with common scoring and geometry modellers, which comes as part of ROOT. ROOT contains isotope decay data and the possibility to describe the evolution of isotopic vectors via Bateman equations. The addition of the ENDF information to Root will allow the development of a transport code for low energy neutrons and other combination of projectile target, either stand-alone as part of the Root system or in combination with some of the other Monte-Carlo systems within the framework of the Virtual Monte-Carlo. KCI Citation Count: 4
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