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S. Miglioranzi (CERN) 36th Software Week

Addressing simulation topics crucial before data collection: energy loss, particle production, validation tools. Enhancing accuracy and adjusting simulation factors for improved results.

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S. Miglioranzi (CERN) 36th Software Week

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  1. Simulation settings and validation infrastructure S. Miglioranzi (CERN) 36th Software Week S. Miglioranzi

  2. Outline • At the latest Software week few simulation-related topics which need to be solved/discussed before the data taking were pointed out: • dE/dx simulation • -rays production switched ON? • Multiple Scattering in MUON system • Likely re-calibration of calorimeters • Validation tools for the Simulation S. Miglioranzi

  3. Energy loss in Si M. Needham • Matt’s studies (T-Rec 26/01/2009) using PGUN (50k muons at fixed Energy), only VELO simulated (results applicable to ST) • Differences of MPV between DC06 and 2008 (G4 9.1) Gauss 24-25: G4 7.1.p03 (DC06) Gauss 30r4: G4 8.3.p01 + EMfast (2007) DC08: G4 9.1.p01/p02/p03 + EMfast • In 2008 (G4 9.1) the width seems to be increased (if anything it seems a bit overestimated now) S. Miglioranzi

  4. Energy loss in Si M. Needham ST: • in DC06 the intrinsic width given by G4 was too small (atomic binding correction was missing) -> in digitization phase smearing applied (VELO and ST) • in 2008 (G4 9.1) G4 simulates the atomic binding (width is close to expectation) -> correction no longer needed.-> Matt’s proposal to turn off the additional smearing accepted. The width seems to be a bit overestimated w.r.t. theory (e.g. for TT ~5%) • still remain problem in VELO simulation: Landau width too wide w.r.t. testbeam Width = Noise*cluster width + Landau width (in quadrature) Landau width= Landau scale + atomic binding S. Miglioranzi

  5. -rays M. Needham (Gauss meeting 09/01/2009) • Still a problem for  at high if -rays OFF! • Agreement with theory ~10% • Turning ON -rays helps a bit • Significant unphysical differences between particle types S. Miglioranzi

  6. -rays in Gauss: how they are steered The production of -rays in Gauss is done forcing the electrons range cut to be ~ mm. Lowering this cut activation of not only -rays but other low energy electrons from other processes (i.e. Bremsstrahlung) . • Simulation.opts defines the general (whole detector) Production Cuts: GiGa.ModularPL.CutForElectron = 10000.0 * m; GiGa.ModularPL.CutForPositron = 5.0 * mm; GiGa.ModularPL.CutForGamma = 10.0 * mm; • DRaysOn-HT.opts, DRaysOn-LT.opts allow to steer the activation of -rays: // Reset production cuts for whole detector GiGa.ModularPL.CutForElectron = 5.0 * mm; GiGa.ModularPL.CutForPositron = 5.0 * mm; GiGa.ModularPL.CutForGamma = 5.0 * mm; • Simulation.xml specify “Volume”-based and “Region-based” cuts: <SimAtt name="SimAttrGlobal" minEkine="1.0*MeV"/> • Only minEKine working on Volume-basis <ProductionCut name="RichAerogelDeltaElectronCut" electronCut="1.5*mm" positronCut="5.0*mm" gammaCut="10.0*mm"/> </ProductionCuts> • Production cuts only can be overwritten on Region-basis S. Miglioranzi

  7. -rays facts M. Needham • ST: turning ON the -rays increases the detector occupancy. • For IT occupancy increased by a relative factor of 10% (1/2 due to -rays). • - For TT it goes up by 20% (1/3 due to -rays). • The STAssociator (MCParticles <-> clusters) was modified in order to count -rays produced in the Silicon as coming directly from the incident primary (same thing should be done in VELO). • VELO: studies are required to investigate the effect on the resolution as a function of pitch and track angle and compared in Boole to match testbeam results • OT: implementation of straws in the geometry description (necessary for correct treatment of -rays) not foreseen in the short-term. With the current geometry a range cut could be added anyway in the digitization to kill lower energy particles that incorrectly transverse many straws. For DC09 the -rays will stay turned OFF (currently only switched ON for RICH Aerogel, possibility to be activated also for other regions). In future productions (even later this year for first data) the sub-detectors should be prepared to have the -rays turned ON -> more realistic simulation. S. Miglioranzi

  8. MCS simulation in G4 • Muon trajectories are dominated by multiples scattering interactions in the Calorimeters and Muon Filters • The MCS in G4 is not correctly simulated in case of dense material and large step sizes (MUON Filters are a perfect example!) -> correlation between displacement and angular deviation not maintained. In G4 the step length is defined using the following criteria: Distance to nearest volume boundary Magnetic field Physical processes (decays, bremsstrahlung, delta rays) The smallest step length is then chosen. • To speed upthe simulation a special “ZeroFieldManager” is applied to the MUON (the field and its map extend only to the front of HCAL). S. Miglioranzi

  9. MCS simulation in G4 Muon Filters length ~80 cm O. Levitskaya • Without -rays only few steps (peak at 80cm = 1 step) inside MUON Filters • Activating the -rays the step length is reduced S. Miglioranzi

  10. MCS simulation in G4 M1 M2 • After Muon Filters the correlations x vs x is spoiled M3 M4 O. Levitskaya M5 S. Miglioranzi

  11. MCS simulation in G4 • The activation of -rays forces G4 to reduce the step length -> correct description of correlation (side effect) • for the MSC starting from g4 9.0 or 9.1 possibility to control the step size but tests needed to understand how to use them inside Gauss/GiGa • -rays will be turned ON. In the future the “activation cut” on the Electron range (5 mm, see previous slides) can be optimized (larger cut) in order to save CPU time. • Include correlation plots in simulation monitoring M3 M3 S. Vecchi -rays OFF -rays ON S. Miglioranzi

  12. Calorimeter Calibration • CALO parameters need to be tuned for simulation/digitization with the new G4 (possible sizeable changes as major changes in EM model in G4 v8) • ECAL and HCAL ActiveToTotalRatio (needed in Boole to convert MC tot Energy deposit into ADC): ADC = (ActiveToTotalRatio*visible Energy)/Gain Evis= a Etot(+b) a-1 = ActiveToTotalRatio for condDB • ECAL Total/Active decreased by 15% w.r.t. DC06 O. Deschamps(CALO meeting 05/02/2009) S. Miglioranzi

  13. Calorimeter Calibration • Sensitive variations of <Evis> with Gauss versions was observed in the past • Dedicated set of PGUN production required with various energy • (from 100MeV to 168 GeV) with no material in front of CALO produced • with Gauss v36r2 -> will allow more detailed analysis to verify new tuning parameters • EXTRA set of Simulation Monitoring plots will be produced to check “steadiness” of the Evis in ECAL and HCAL running over different Gauss Versions/cuts (suggested by V. Romanovsky): • <Evis>/P vs P • sigma(E)/E vs P O. Deschamps (CALO meeting 02/05/2009) S. Miglioranzi

  14. Development of Simulation Monitoring Tools • Python script to analyse the Gauss log files and rootople (SimulationReferencePlot.py) will be available in a future Gauss release as a dedicated package • Comparisons of different Gauss versions and different CUTS (-rays ON/OFF, HT/LTKine...) inside the same version are shown • For each comparison a web page with links to the monitoring plots/tables is created and added to the main webpage (http://lhcb-release-area.web.cern.ch/LHCb-release-area/DOC/gauss/simulation/validation/index.html) S. Miglioranzi

  15. Simulation Monitoring Tools • The background color of the histograms indicates the result of the Kolmogorov test for the comparison. • gifs of the comparison open up S. Miglioranzi

  16. Simulation Monitoring Tools • Gauss errors/warnings/exceptions monitoring available (with dump of the log file error list) • Useful to detect particle stuck/overlaps etc... S. Miglioranzi

  17. Simulation Monitoring Tools • Gauss summary tables (versions, average # hits, timing...) are extracted from log files: S. Miglioranzi

  18. Simulation Monitoring Tools pi+pi- (LHEP+EMopt1+DRays OFF+KineHT) pi+pi- (LHEP+EMopt1+DRays ON+KineHT) • How can we monitor the -rays? ->ST dE/dx summary table (MCHitMonitor updated by Matt) are extracted from log file: • MPV vs  plots can be produced for different Gauss versions/cuts for all the different validation samples (python script running over the web pages info). S. Miglioranzi

  19. Simulation Monitoring Tools What was observed in the last days monitoring the MC truth plots: REFERENCE: MINBIAS (LHEP+EMopt1+DRays OFF+KineHT) CURRENT: MINBIAS (LHEP+EMopt1+DRays ON+KineHT) • Peak at -5000mm when -rays ON. They seem to escape the EndOfTheWorld cuts (SpecialCuts.cpp) • aParticleChange.Initialize(aTrack); • aParticleChange.ProposeEnergy(0.) ; • aParticleChange.ProposeLocalEnergyDeposit(aTrack.GetKineticEnergy()) ; • // By default kill the particle to prevent it from decaying • aParticleChange.ProposeTrackStatus(fStopAndKill); • return &aParticleChange; • . • Debugging to understand why turning -rays on produces the -5000mm peak S. Miglioranzi

  20. Summary • Sub-detectors need to be prepared to turn the simulation of -raysON (not for DC09 but sometimes this year, before the data taking) • monitoring of dE/dx (-rays ON-OFF) in Gauss output has started (ST) • MCS: the -rays will be turned ON in MUON Filters (correct step size), Electron cut will be optimized • Updated correlation studies using latest Gauss versions are being produced (S. Vecchi) and set as part of the routine simulation validation • CALO simulation parameters need to be retuned using latest G4. Monitoring of Evis will be set up. • News on next releases of G4 S. Miglioranzi

  21. Geant4 9.2 • New Multiple Scattering process and model: - G4eMultipleScattering specialized for simulation of e+e- -G4WentzelVIModel for multiple scattering of muons and hadrons (old MCS model frozen, still available) • LHEP Physics List revision only in 2010 (tests will be needed to define which is the best hadronic physics list to adopt - especially K interactions). • G4 9.2 and next releases on SL5 (no longer on SL4) • Support with bug fixes, evolution for 9.2 up to the end of 2010 (as requested by the experiments) • As soon as DC09 starts, tests on G4 9.2.pXX will begin -> depending on validation, transition before data taking starts is foreseen G4 Technical Forum: http://indico.cern.ch/conferenceDisplay.py?confId=53521 S. Miglioranzi

  22. backup S. Miglioranzi

  23. sigma(theta) vs P • sigma(X) vs P S. Miglioranzi

  24. Peak at -5000mm is due to -rays activation • Differencence between HT-LTkine (-rays ON in both cases) visible in the chambers. S. Miglioranzi

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