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Status of Geant4/Simulation activities and future prospects

Status of Geant4/Simulation activities and future prospects. J. Apostolakis PH/SFT. Overview. The Geant4 toolkit and SFT Areas of SFT involvement Status for LHC production open issues and ongoing actions Future perspectives The LCG simulation project GENSER - Event Generator

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Status of Geant4/Simulation activities and future prospects

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  1. Status of Geant4/Simulation activities and future prospects J. Apostolakis PH/SFT

  2. Overview • The Geant4 toolkit and SFT • Areas of SFT involvement • Status for LHC production • open issues and ongoing actions • Future perspectives • The LCG simulation project • GENSER - Event Generator • Physics Validation • Manpower

  3. 1. Geant4 toolkit and SFT The Geant4 Toolkit Areas of SFT involvementGeant4 Reviews

  4. The Geant4 toolkit: an overview • Designed for HEP • Especially LHC and future experiments • nuclear physics, heavy ion experiments, • also medical physics, space application. • Open Architecture and full capabilities • Flexible kernel, enabling ‘any type’ of application • Powerful geometry modeler • Physics models for EM, hadronic, weak interactions • Choices with different accuracy, CPU performance needs, .. • OO used to decouple implementations of physics models, geometry shapes & navigation methods, .. • Developed by the Geant4 collaboration • About 90 physicists & computer scientists from HEP institutions & agencies, ESA and universities around the world.

  5. Involvement of CERN in Geant4 • Team in IT (1994-2002), moved to PH/SFT (2003) • Constant focus of Simulation/G4 team on LHC and HEP • Driven by LHC use/issues, physics and capability needs • From RD44(1994-98) – with all LHC experiments as alpha users, • through the G4 production ramp-up phase (1999-2003) to today. • Initiative on Test Beam Comparisons (2000) • Later part of Physics Validation in LCG Simulation Project • New models for physics accuracy - at best CPU cost possible • Introduce new Physics models, then push for optimisation of CPU • Developing functionality for additional use cases • E.g. biasing, scoring & parallel geometry for (cavern) background • Liaison and support on all issues encountered by LHC experiments • Geant4 in production use by ATLAS, CMS, LHCb since 2004 • The engine of the detector simulation • Enabled use of Geant4 in Root Virtual Monte Carlo (VMC) • for use by ALICE, others

  6. Areas of Work of PH/SFT • Coordination, release preparation (staff) • G4 Spokesperson/SB Chair, Release manager/QA • Physics Validation (mix of staff/associates/fellow) • Thin-target benchmark data • Physics Model improvement (mainly by associates) • Hadronic: String models, cascade, CHIPS • EM Physics: Standard (HEP) • Geometry (mix) • Navigation; solids; tracking in field; persistency. In the above areas support and maintenance are included - and are an increasing fraction – as well as validation, testing and development. • Testing: nightly integration tests, regression & release validation • Hosting web site and development tools • Contribute also to other areas, e.g. • Performance improvement – collaborating with FNAL experts, LHC teams • Training courses;multithreading prototype studies, ..

  7. Geant4 External Delta Review 2009 • Organized by the Geant4 Oversight Board • Followed Geant4 Review 2007 • Previous reviews: 2001 full, 2002 delta • Addressed issues relevant to HEP users, medical & space communities • Reviewers from Atlas, CMS, Alice, medical, space, hadronic MC code. [ 6 from HEP / 9 total ] • Topics covered included: • EM & Hadronic physics, validation, computing performance, documentation. • Report made 22 recommendations • 2009 actions underway • Next actions to be formulated at Collaboration meeting (Oct 2009)

  8. 2: Geant4 status for LHC production Overall StatusOpen Issues & Ongoing Actions

  9. Geant4 Status for LHC: 1 • Geant4 latest releases in production in ATLAS, CMS and LHCb • All ongoing/starting productions with Geant4 9.2 (Dec 08) + patches • Agreement to support 9.2 until Dec 2010 for LHC experiment use. • Enables complex geometrical descriptions • From 10 microns to 100 meters (detector) and more • Robustness in production • Most productions see event failure rates below 10-5 • Occasional issues tracked down and addressed promptly • Combining ever better physics and low CPU is hard • Experiments choose ever-better models for physics reasons • So performance (CPU & memory use) was/is/will be a key challenge • EM processes targeted for LHC/HEP are ready • Extensively validated at percent level • Benchmark data and experiment test beams • Some models are being improved, refined • Large suite of benchmark (including simplified versions of LHC calorimeter)

  10. Hadronic models and Physics Lists • Physics accuracy goals: • Describe known thin target data and test beam data • Predictive power for unmeasured regions. • Hadronic Models have limitations and applicable energy range • Our physics lists mix different models Today’s physics list QGSP_BERT has transitions between: • High-energy : string models (QGS) • Intermediate: parameterised (LEP) • low energy: cascade (BERTini) All feed into de-excitation models (Preco) • QGSP_BERT(_EMV) physics list is used in production • By LHC (and other HEP) experiments • Also tried/used in other applications • Studies with other physics lists ongoing.

  11. Geant4Status for LHC: 2.Hadronic Physics • Accurate Modeling is important tool • For calibration, energy scale, jets, missing ET , t • Many or most observables are modeled well (or adequately) • Energy response (E>20 GeV) and p/e, • Shower profile for pion projectiles. • Resolution (typically smaller than data), • Some quantities have deficiencies • Shower profile for protons • Energy response (8-20 GeV). • Following slides illustrate some results & issues • Concentrating on open issues and investigations • Comparisons with data are taken from presentations by experiments at LCG Physics Validation meetings (recent, preliminary results) • Result of test beam comparisons of ATLAS, CMS – in close contact

  12. Pion longitudinal shower profile in stand-alone ATLAS TileCal test-beam at 90o Thanks to Atlas Tilecal Data MC within ~ ±10% up to 10 λ. For Protons : -(20%-40%) at 10 λ.

  13. Energy response and transitions ATLAS Tile • CMS & ATLAS reported energy response shows unphysical features • Kink (9 GeV) • Change of slope (25 GeV) • These are the transition points between models • Reproduced in simple setups • No detector effects Problem of matching models:

  14. p- Fe : p0 Investigation into energy response • Study fraction of energy going into different particle types • for each hadronic model • Identified microscopic reasons for transition issues • Which differences of models • Identify potential anomalies • Confirmed known model limitations & find new ones Study single interaction: p- on Fe

  15. p- Fe: p Actions • Search for thin-target data • To distinguish between models • To enable tuning / improvement • Find models that need replacing • LEP disagrees with benchmark data • Assess potential alternatives • QGS/Chips smoother than QGS/P • FTF spans from 3 – 20+ GeV • Prepare Revised physics lists • Seek feedback from LHC experiments • Improve physics models

  16. 3: Geant4 for LHC, sLHC and ILC Future perspectives

  17. Evolving needs, requirements • LHC experiments needs during first years • Expanded Support in most areas – especially physics • Identify source (& fix) discrepancies with data • Improvement of hadronic and EM modeling • High Stability & Robustness for large MC productions • Performance improvement (CPU, memory) • LHC upgrade, ILC detectors, other • Refined hadron shower modeling • Better lateral profile (ILC), .. • Part of EUDET project since start (2006); CALICE contacts • Comparison with CALICE data probe different aspects of hadronic showering – resulting future improvements in models can benefit LHC • We are following these key (physics) issues • And will continue to do so – to the degree that manpower will permit.

  18. Key future areas for SFT G4 team • Support/Maintenance • In our main areas (Geometry, Physics) and beyond; • Performance improvement • Physics Validation & Improvement • Hadronic Physics: Models & Combinations (lists) • Identifying limitations and their causes (major role) • Contributing to improving models • Geant4 Architecture Review (start: 2010) • Participate in planned major overhaul • Address design issues, drive to improve implementation • Integration & interaction with other SFT tools/projects • Latest: migration to SPI nightly testing system (2008/9); • Multi-threading and multi-core: Geant4 as proto-project.

  19. Our Major Challenges • Depth of expertise in high-energy nuclear physics • Experts with 10s years of experience few • Several working for other projects (e.g. MCNP), • Limitations of associates contracts. • Simulation codes / models • Several projects focused on model improvement on ion-ion (UrQMD) or cosmic rays (QGSJET) • Data for validation of diffraction, p0 production, .. • Difficulty to access data of some old experiments • Measurements of HELIOS (diffraction on nuclei), • Published data apparently corrected with faulty MC; • Search for data of p0 production (ANL?). • Increased load of maintenance • Author/developer departures • Reduced manpower

  20. Search for experts/expertise • Developed relations with model authors, experts • Liege cascade (INCL) team • A. Boudard (Saclay) joined Geant4 • INCL ported to Geant4; developments ongoing • D. Cano (CIEMAT): low energy neutrons • New databases for neutrons E < 20 MeV • Recruited to Geant4, amongst others • J.M. Quesada Molina (Univ. Sevilla) • Made full revision of pre-compound (the P in QGSP) & evaporation • Interfaces to other models • DMPJET II.5: first for ion-ion (space funding) • Plan to extend it to hadron-ion

  21. Communication • Regular contacts with LHC experiments using G4 in production (ATLAS, CMS, LHCb) • Many questions answered and issues addressed; • Liaisons in Atlas (JA), CMS (GC): attend experiment simulation meetings, .. • Dialog with FLUKA team in context of Simulation project • Focus on validation of models; physics issues. • Collaboration with IT • Extensive & fast testing of each Geant4 Release using WLCG (+OSG); • Work with Openlab on Performance (sequential & multithreaded). • Physics Validation Meeting • Forum for Physics issues, validation including test beams • Increasing channels with CALICE/ILC • EUDET(2005), CALICE meetings (Mar & Sep 2009), CERN group. • Geant4 Open User ‘Technical Forum’ since 2003 • Spreading information of experience by HEP experiments, other users • Agrees priority on ‘big’ requirements, feeds into Geant4 workplan.

  22. Communicating within Geant4 • In close contact with many Geant4 contributing teams/people, e.g. • SLAC: hadronics (including neutrons), kernel, Vis • KEK/Japan: kernel, particle properties, GUI • FNAL: hadronics, performance improvement • IN2P3 & INFN: EM Standard(HEP+), EM Low-Energy • Northeastern Univ.: multi-core and multi-threading • These are in addition to formal channels: • Steering Board • Working group meetings

  23. 4: The LCG Simulation Project Brief Overview Event Generator Service

  24. LCG Simulation Project • Part of LCG Application Area that spans simulation • Encompasses • SFT involvement in Geant4 and its support for experiments • GENSER Event Generator Project • Hosted T. Sjöstrand- Pythia 8 development. • Physics Validation (Geant4, Fluka) • cross-comparisons on thin-target data • Joint effort on test beam comparisons • Regular meeting including LHC (& other) experiments • Garfield • FLUKA – liaison with CERN Fluka team. • Led by Gabriele Cosmo

  25. LCG Generator Services: motivation • Provide: • a repository of validated MC event generators, and • related tools, • useful for the experimental and theoretical LHC communities. LCG Simulation Project

  26. LCG Generator Services: status • GENSER • Structure stable and used by experiments (ATLAS, CMS, LHCb) • 25 generators installed (most of them with several versions) • Platforms supported: SLC4 and SLC5, 32- and 64-bits • For some generators, also Windows and Mac OS X • New versions are installed as they are announced and tested • regression testing with respect to a reference version) • Status of the generators and testing available on the Web • Project planning meetings twice per year • Regular monthly technical meetings • HepMC • Standard interface used heavily by the LHC community • Meetings every 6 months to decide new releases (latest: 2.05, June 09) • MCDB • Used in CMS productions LCG Simulation Project

  27. SFT members working in SIM/G4 • Staff • JA: Geant4 spokesperson (Steering Board chair), geometry, hadronic physics. • Gabriele Cosmo: release manager, geometry coordinator, quality assurance. • Gunter Folger: hadronics, integration testing, software tool manager. • Alberto Ribon (LD - Dec 09): SIM physics validation project, GENSER Event Generator service, G4 hadronic physics, Grid release validation. • Associates • Vladimir Ivantchenko: EM coord. (HEP focus) + Hadronics; CMS 2nd contact. • Mikhail Kossov: Hadronic physics, validation & CHIPS model. • Vladimir Uzhinskiy: Hadronic string modeling & validation • Fellow(s) • Andrea Dotti (July 09-): Hadronic validation & physics (diffraction.) • Students • Gabriele Camellini: Geometry & FLUGG (Fluka with G4 geometry) • Victor Diaz: System Integration Testing (incl. move to SPI nightly system) • Mary Tsagri (doctoral/MC-PAD): Modeling of neutrons in Gas detectors

  28. Manpower: 2005-2010 • Profile 2005-2009 • Staff departures (not replaced) • Retirement of Geant4 testing coordinator (Mar 2008) • LD: Simulation/GENSER coordinator (Jan 2008) • Sparser fellows • Decline in number of associates • Upcoming changes (end-2009) • Departure of A. Ribon (LD) - post was opened. • End of several associates contracts.

  29. Summary • Geant4 new releases in production in ATLAS, CMS and LHCb • Robustness, improved performance • Comparisons with benchmark data & LHC exper. test beams • Good agreement in many quantities, discrepancies in others • Key issues are being investigated, in particular model transitions • Ongoing improvement and preparation for support of LHC experiments’ data-taking • Challenges anticipated • Enabling existing model authors to contribute closely • Enabling collaboration with additional physics experts • Finding key data for comparison • Address new needs of future experiments

  30. Backup slides

  31. Areas of Work & people • Coordination, release preparation • G4 Spokesperson/SB Chair (JA), Release manager (GC) • Hadronic Physics: • String models: V. Uzhinskyi (PJAS: 2009-), GF • Cascade: GF; CHIPS: M. Kossov (PDAS) • Validation: AR/new staff; A. Dotti (fellow) • EM Physics: • Coordinator: V. Ivantchenko (PJAS: 2005-2009) • Geometry • Coordinator (GC), deputy (JA), G.Cam.(student) - had fellow • Testing: integration tests, release validation

  32. Commonality of many issues • Between LHC and other HEP experiments • Hadronic physics is the same and experiment needs for good modeling is invariant • Also high precision in EM physics is a challenge • Also with many other users • Physics below 10 or 1 GeV is very relevant for energy deposition, fluctuations, missing energy, .. • Low-energy (<1 GeV) hadronic physics is common • model improvement helps most/all users • Need for CPU-performant models in common energy domain is widespread (HEP, medical phys., ..)

  33. Hadronic Shower Profile: short history • Issue of early short hadronic showers(2004): QGSP • Addressed: added physics model, improvements • Introduced cascade (BERTini) – and improved it • Added Quasi-Elastic channel - to QGS model (2007) • Agreement is better with QGSP_BERT • Pionshower profile within 10% at 10 lambda • Proton profile 20-40% low at 10 lambda • Looking to improvements in diffraction to address this • Develop(ing) Fritiof(FTF) model as alternative • Better results for protons than QGSP_BERT

  34. Proton longitudinal shower profile in stand-alone ATLAS TileCal test-beam at 90o MC: -20% to -40% at 10 λ.

  35. Pion energy response in ATLAS barrel combined test-beam G4.9 Bertini cascade model increases the response. QGSP_BERT shows the best overall performance for the linearity (within 4%). 2% above 10 GeV 4% below 10 GeV

  36. Open Issue: Energy response 8-20 GeV • Reports from CMS and ATLAS • Non-monotonic energy response 8-12 GeV • Kinks in response in transitions of physics models • Actions • Confirmed in simple setups • Investigations of properties of physics models • Identified issues with particular models • Feedback to improve modeling • comparing with thin-target data

  37. Pion energy response in ATLAS stand-alone test-beams G4.9 Tile HEC Bertini cascade increases response for Tile and HEC by 4-5%. In Tile and HEC response ~2% too high with QGSP_BERT.

  38. Pions and protons energy response in CMS combined test-beam 4.9.2.b01 ECAL+HCAL ECAL(mip)+HCAL Agreement between data and simulation on energy response is within systematic uncertainty

  39. p- Fe : p- Investigation into energy response Leading Particle • Study fraction of energy produced in reaction • for individual model level • Plot the sum of the energies of the secondaries of one particle type (e.g. p0 or protons) • <SEpi-zero> / Ebeam • p0 production responsible for most early energy deposition • Transitions in QGSP_BERT • BERT to LEP between 9.5-9.9 GeV • LEP to QGS/Precobtwn 12-25 GeV Pi- beam on Fe (one interaction)

  40. p- Fe : p+ • G4 Bertini cascade (BERT) • Has large excess of energy in protons and neutrons for E>3 GeV • Revision is underway (@ SLAC) • QGS/Chips smoother than QGS/P • Appears plausable for E>10 GeV • LEP disagrees with other models • Looking to replace it (with FTF) • Revised physics lists prepared • First feedback from LHC experiments • Need data to compare (spectra) • Especially those relevant to p0 production (e.g. p+ + p- Some key observations / issue(s)

  41. Pion resolution in ATLAS stand-alone test-beams HEC Tile Bertini cascade makes resolution better: in Tile: better agreement with data (±10 %‏). in HEC: MC resolution too good by -10%.

  42. Pion resolution in ATLAS barrel combined test-beam Bertini cascade makes resolution betterMC predicts too good resolution -5 ÷ -10%

  43. Pions and protons energy resolution in CMS combined test-beam ECAL+HCAL ECAL(mip)+HCAL Resolution is too good in Monte Carlo

  44. Pion lateral spread in stand-alone ATLAS TileCal test-beam @90o Bertini cascade makes shower wider, which is in better agreement with data, but data are still a bit wider.

  45. Test Beam Comparisons: Short Summary and Outlook • The LHC experiments have carried out extensive tests of the Geant4 physics models and validated them with test beam data. • ATLAS and CMS have chosen QGSP_BERT(_EMV)as the default Physics List.Fritiof-based Physics Lists, FTF_BIC and FTFP_BERT show interesting features. • There are some remaining issues in hadronic physics • 1) Discontinuity in energy response at the model boundaries • Proton longitudinal shower profiles are shorter than data in QGS-based Physics Lists (diffraction) • Lateral shower profiles are a bit narrower than data(not an issue for LHC experiments, but for ILC it could be important….)

  46. Hadronics: Key issues & Recent aspects • Identifying source of physics deviations • Typically many sources could contribute • Deficiencies of hadronic models • Responsive to tuning, or • Intrinsic model limitations? • Transitions between hadronic models • Trying to match mean, RMS, of diverse observables • Extending Validation • More benchmarks, observables • New data • Shower shape (p good, proton fair) • Investigating diffraction • Simplification in older modeling • LEP Energy non-conservation • Cascade nucleon production. • Steps or ‘Discontinuities’ • Energy Response (Atlas, CMS) • In region 8-12 GeV • Comparisons • With FNAL & ITEP data 3-10 GeV • With fine grained CALICE data. Key Issues: ongoing Recent aspects (for each)

  47. Geant4 Review 2009 outcome • Made 22 recommendations • Covered 8 different areas: • EM physics • Hadronic physics • Computing Performance • Physics Validation • Release Validation • Documentation • User Support • Resources.

  48. Geant4 Review 2009Major recommendations • Removal of less accurate EM models/options (overall simplification of choices where possible) • Provide guidance to users for available EM models and options • Study assumptions and parameterisations of physics models in FLUKA and improve corresponding hadronic models available in Geant4, where needed • Continue in monitoring CPU performance, perform code reviews for improvement • Development of multi-threading capability in Geant4 • Conduct a code design assessment in view to also integrate thread-safety in code • Consolidation of the hadronic WG and low-energy WG web pages

  49. Geant4 Review 2009Major recommendations - 2 • Provide pointers to physics benchmark results and tests and related documentation • Adopt a range of metrics to characterize as broad a range of validation results as possible • Acquire/redirect resources to improve documentation and keep up with updates • Adopt periodic review of the documentation and improve documentation design • Identify new tools to adopt for the software installation • Involvement of the user community in the log-term support of physics models • Seek for additional support from all available sources; extend the Collaboration to new Institutions

  50. Geant4 Architecture Review • Focus areas of InternalGeant4Review: • Key interfaces • Design of Geant4 kernel • Goals (proposed) • Streamline design for features added 1998-2009 • Further improve performance, robustness • Enhance maintainability, test-ability • Adapt for multi-core / multi-threading • Evaluate other recent / new technologies. • Effort to be in parallel with • Support for existing Geant4 version(s) in production.

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