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Physics of LHC Experiments: Utilizing OSG Resources

This presentation explores how LHC experiments will use OSG resources and the role of the Open Science Grid in particle physics research.

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Physics of LHC Experiments: Utilizing OSG Resources

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  1. LHC PhysicsorHow LHC experiments will use OSG resources • OSG Consortium Meeting • 08 / 21 / 06

  2. Particle Physics • Probe innermost structure and explain it from first principles 08/21/06 Oliver Gutsche - LHC Physics

  3. Standard Model • Current description of matter: • 12 elementary particles and their anti-particles • 4 force particles carrying the 3 dominating forces (at scales investigated) 08/21/06 Oliver Gutsche - LHC Physics

  4. LHC, the discovery machine • What can the LHC add to the current picture: • Higgs: explain the origin of mass • Super-Symmetry: beyond the standard model 08/21/06 Oliver Gutsche - LHC Physics

  5. LHC • Large Hadron Collider • Proton-Proton collisions • Beam energy: 7 TeV • Circumference: 27 km • Bunch crossing rate at interaction regions: 40 MHz 08/21/06 Oliver Gutsche - LHC Physics

  6. Outline • Example for Higgs discovery channel • Analysis and requirements • Computing • CMS Metrics • CMS computing model • The role of the T2 centers • OSG contribution • User use case • Services Challenges and current status • Summary & Outlook Apologies to the other 3 experiments, following talk mainly concentrates on CMS 08/21/06 Oliver Gutsche - LHC Physics

  7. Example Signal: H→ZZ(*)→4μ • Signal Reconstruction strategy: • Reconstruct 4 μ (2 μ+, 2 μ-) • combine each 2 μ to Z • combine 2 Z to H 08/21/06 Oliver Gutsche - LHC Physics

  8. Event display 08/21/06 Oliver Gutsche - LHC Physics

  9. Backgrounds and Analysis Strategy • Signal overlaid by background events which produce similar signature in detector • Analysis Strategy: • Record data with detector • Simulatebackground and signal events • Extract signal from recorded data using the background simulation 3 main background tt Zbb ZZ 08/21/06 Oliver Gutsche - LHC Physics

  10. Data taking vs. MC production High Level Trigger Reconstruction primary datasets Data Taking Generation and Simulation Reconstruction MC datasets MC production 08/21/06 Oliver Gutsche - LHC Physics

  11. Data tiers SimFEVT (full simulated event) FEVT (full event) RECO RECO-SimEvent SimEvent RAW AOD AOD 08/21/06 Oliver Gutsche - LHC Physics

  12. Disk requirements • Detector output rate after trigger: 150 Hz for all running conditions (low luminosity, high luminosity) • Extrapolated beam time: • Events from data taking: • Events from MC production: • Total: 08/21/06 Oliver Gutsche - LHC Physics

  13. CPU requirements • Assume Core in 2007: 2000 SI2K (optimistic) • Single Core Pentium IV 3 GHz ≈ 1300 SI2K • Time to reconstruct event • 78 kSI2K s/ev • On demand reconstruction at 150 Hz • 11.7 MSI2K ≈ 5850 Core’s • Time to simulate and reconstruct event • 234 kSI2K s/ev => 1 Core ≈ 270,000 ev/year Reconstruction and MC production Analysis • Single Analysis has to access one primary dataset and the MC samples • Assume: • Analysis needs access to AOD • Every 3 days • Selection has to be finished at least after 3 days • Analysis needs access to RECO • Every 7 days • Analysis has to be finished at least after 7 days • Selection time: 0.25 kSI2K s/ev • Analysis time: 0.25 kSI2K s/ev 08/21/06 Oliver Gutsche - LHC Physics

  14. CMS Grid Tier Structure T2 T2 T2 T2 T2 T2 T1: USA T2 T2 T1: Italy T1: France T2 T2 T0 T2 T1: Germany T1: Spain T2 T2 T2 T1: UK T1: Taiwan T2 T2 T2 T2 T2 T2 T2 T2 08/21/06 Oliver Gutsche - LHC Physics

  15. Data flow • T0 distributes RAW and reconstructed data to T1’s(subset of the primary datasets, full AOD copy) • T2’s are associated to specific T1 which provides support and distributes data(simulated MC is transferred back to associated T1) 7 T1 25 T2 • substantial computing resources are provided by the T1’s and T2’s • CMS-CAF performs latency critical activities like detector problem diagnostic, trigger performance service, derivation of calibration and alignment data 08/21/06 Oliver Gutsche - LHC Physics

  16. US contribution to CMS Tier structure • U.S. contribution to CMS tier structure • T1 at FNAL • 7 associated T2 sites (OSG) Wisconsin MIT T2 FNAL Nebraska T2 T1 T2 T2 Purdue CALTECH T2 San Diego T2 Florida T2 08/21/06 Oliver Gutsche - LHC Physics

  17. CMS Computing Infrastructure • Core Infrastructure • DBS: Data Bookkeeping System • official catalog of available datasets and MC samples • organizes datasets and samples in fileblock containing files • DLS: Data Location Service • catalog of which storage elements contain specific datasets and MC samples • TFC: Trivial File Catalog • files are stored in a CMS specific namespace which is reproduced at the storage elements at every site • Access to files in the CMS namespace is resolved by the CMS applications automatically prepending site specific locations and access protocol using a local site configuration CRAB PhEDEx ProdAgent GRID Middleware DBS DLS Site Resources batch-system TFC CPU Disk 08/21/06 Oliver Gutsche - LHC Physics batch-system

  18. CMS Computing Infrastructure • Computing Systems • PhEDEX • Transport any dataset or samples registered in DBS between sites • MC production system (ProdAgent) • Produce MC samples in centralized way • User Analysis Tool (CRAB) • enable user to execute his analysis code on any sample registered in DBS/DLS CRAB PhEDEx ProdAgent GRID Middleware DBS DLS Site Resources batch-system TFC CPU Disk 08/21/06 Oliver Gutsche - LHC Physics batch-system

  19. Site requirements • CMS T2 site • CPU: 1 MSI2K • DISK: 200 TB • Network: 2.5-10 Gbps • OSG middleware stack • Computing Element (CE) • Storage Element (SE) • Batch system • OSG sites: Condor and PBS • Mass Storage system • OSG sites: dCache (tapeless) • CMS software installed by central instance (OSG sites: $OSG_APP) including TFC setup • Opportunistic usage (OSG) • Useable for MC production • OSG middleware stack • Computing Element (CE) • Outbound connectivityof workernodes (stage-in and out) • CMS software installed by central instance (in $OSG_APP) 08/21/06 Oliver Gutsche - LHC Physics

  20. User analysis • Task • Discovery of the Higgs in channel • H→ZZ(*)→4μ • Approach: • use recorded and reconstructed data from detector • use produced MC samples • reconstruct 4μ signature and extract Higgs mass OLI 08/21/06 Oliver Gutsche - LHC Physics

  21. ideal MC workflow • MC samples: • Produced by MC production system at T2 level • Archived at T1 which stores corresponding datasets • MC production requests • Initiated by the physics groups • Samples are probably more general than needed • Physics groups and users • Prepare skimsof the MC samples at T1’s for specific physics purposes • Complete skims are transported to dedicated T2’s. • Useranalyzes MC samples by processing skims at T2’s 08/21/06 Oliver Gutsche - LHC Physics

  22. ideal Data workflow • Data • Recorded by the detector • Triggered by the HLT • Reconstructed at T0 • Split into primary datasets • Distributed between T1 centers • Most analysis only needs to access one of the primary samples • AOD is sufficient for 90% of the analysis • Physics groups and users • SkimAOD of primary samples at T1’s • Complete skims are transported to dedicated T2’s. • Useranalyzes data samples by processing AOD skims at T2’s data taking hasn’t started, for now just a event display of a cosmic muon 08/21/06 Oliver Gutsche - LHC Physics

  23. Special tasks • Alignment/Calibration • In general, alignment/calibration is calculated at T0 or T1 for immediate usage during reconstruction • Parts of RAW data samples can in addition be transported to dedicated T2 to calculate improved alignment/calibration constants • Reprocessing of data • Data samples are planned to be re-reconstructed with improved alignment/calibration and reconstruction algorithms 3 times a year on T0 and T1 level • Reprocessing requires re-skimming of samples Alignment / Calibration Reprocessing 08/21/06 Oliver Gutsche - LHC Physics

  24. Startup scenario • During startup of LHC, no experience with the detector and its output will exist • First calibration/alignment calculations will be not sufficient for analysis • RAW data samples will be transported to T2’s to: • Understand the detector • Improve the reconstruction algorithms, calibration and alignment • Extractfirst physics messages • T1 resources • Used more for analysis than skimming and re-reconstruction (less resources needed by default operations). • Re-reprocessing will be more frequent but short running time hasn’t produced large amounts of data yet AOD RAW 08/21/06 Oliver Gutsche - LHC Physics

  25. Service Challenges • To prepare for the startup, the experiments exercise their systems in dedicated service challenges • CMS currently runs “Service Challenge 4” (SC4) which consists of the exercise of: • the dataset transport system PhEDEx with emphasis on all possible transport endpoint combinations (T0, T1, T2) • the MC production system by running ~12,500 MC production jobs per day on LCG and OSG resources and to produce MC samples for the upcoming challenge • the analysis infrastructure by running ~12,500 analysis jobs per day on samples distributed to every center • CMS’ next challenge is CSA2006 in the fall which exercises the full workflow • feeding MC samples to the HLT and reconstruction at T0 centers • Reprocessing, skimming at T1 centers • Analysis and MC simulation at T2 centers • Sample transportation between the individual centers 08/21/06 Oliver Gutsche - LHC Physics

  26. First MC production run: OSG summary • First MC production run: ~2 weeks of August • Total: 45 Mio. events, OSG (incl. FNAL): 17 Mio. events • More details in Ajit Mohapatra’s talk on Wednesday 08/21/06 Oliver Gutsche - LHC Physics

  27. Analysis infrastructure: grid-wide performance • Automated systems (JobRobots) achieve grid-wide performance close to goal of 12,5000 jobs per day • scale at ~10,000 jobs per day for 5 days and improving Overall Job statistics Job Success Statistics GRID Success Statistics 08/21/06 Oliver Gutsche - LHC Physics

  28. Analysis infrastructure: OSG-wide performance • Scale at ~3,000 jobs per day for 5 days • OSG sites contribute large percentage of overall analysis performance Overall Job statistics Job Success Statistics GRID Success Statistics 08/21/06 Oliver Gutsche - LHC Physics

  29. Analysis infrastructure: OSG site performance • Example: Nebraska: • scale between 450 and 850 jobs per day • high success rates • Other OSG sites show similar performance Overall Job statistics Job Success Statistics GRID Success Statistics 08/21/06 Oliver Gutsche - LHC Physics

  30. Summary & Outlook • Computing for the LHC experiments is large and globally organized • LHC computing marks the final change in high energy physics from the host laboratory centered analysis of data to a global approach • GRID resources and OSG resources in particular will be used efficiently to perform standard production and analysis as well as special tasks • Analysis will be a challenge, not only from the physics point of view but also from the computational requirements and specialties 08/21/06 Oliver Gutsche - LHC Physics

  31. In the end ... • We hope to make many discoveries in particle physics with LHC data using OSG resources 08/21/06 Oliver Gutsche - LHC Physics

  32. The end 08/21/06 Oliver Gutsche - LHC Physics

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