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TRD Status

This report summarizes the TRD status and offline week activities including investigations of detector response, energy loss simulation, non-isochronity of drift, position resolution studies, space charge effects, trigger simulation software, and fast simulation.

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TRD Status

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  1. TRD Status Christoph Blume ALICE Offline Week 8.3.-12.3.2004

  2. Detector response Energy loss simulation Non-isochronity of drift Position resolution studies Space charge effects Trigger simulation software Fast simulation Outline

  3. Detector ResponseEnergy Loss Simulation • Investigation by Ken Oyama • Old AliRoot Implementation: • Microscopic approach in StepManager • Energy distribution for delta-electrons: Ermilova • Energy loss simulation did not match test beam data (too high in simulation) • Mismatch in threshold for delta-electron production: GEANT  StepManager, now both 50keV

  4. red : Ermilova black: GEANT3 2 GeV/c pion Detector ResponseEnergy Loss Simulation: Ermilova  Geant3 Plot (c): Ermilova: Mean=128.5 eV GEANT : Mean=230.3 eV # of primary collisions for 2.0 GeV/c + from Bethe Bloch: Ermilova: 52.7/cm GEANT: 21.9/cm Most probable energy loss: Ermilova: 14.80.02 keV GEANT: 10.10.02 keV Overcompensation by different Bethe Bloch.

  5. TEC entrance track TEC exit Detector ResponseEnergy Loss Simulation: New Implementation by K. Oyama • Energy loss simulation • Use Geant3.21 dEdx calculation instead of current microscopic simulation (Ermilova) • Change scheme to fixed step sizes • Determine optimal size (1mm): data volume  resolution • Study of point resolution for inclined tracks • Implementation in StepManager() • Reduces volume of TRD hits • Keep microscopic scheme as an option (with Geant3.21) a trackpart with ~1 mm length. 4 ~ 7 p.c. are involved.

  6. Mean=16.3 keV RMS=4.6 keV Mean=16.3 keV RMS=4.6 keV Mean=16.3 keV RMS=5.2 keV 2 GeV/c pion ss=0.1 mm MP=10.2 keV ss=1.0 mm MP=13.4 keV ss=5.0 mm MP=13.2 keV Mean=16.1 keV RMS=5.4 keV Mean=17.8 keV RMS=5.4 keV Mean=18.1 keV RMS=6.0 keV Detector ResponseEnergy Loss Simulation: Step Size Dependence

  7. Test Beam Detector ResponseNon-Isochronity of Drift Resolution depends on distance to wire Simulation with GARFIELD Va = 1.55kV, Vd =-2.1kV, Xe-CO2 85-15

  8. Detector ResponseNon-Isochronity of Drift: Implementation by C. Lippmann • AliTRDparameter.cxx: • Update of pad response • New functions: SampleTimeStruct() Fill Array SetTimeStruct(Int_t timestrOn = 0) Switch On the Non-Isochronity TimeStructOn() Is switched on? SetStaggering(Int_t staggOn = 0) Switch On Staggering StaggeringOn() Is Staggering On? SetAnodeWireOffset(Float_t offset = 0.0) Set the distance to the edge of the first pad of the first anode wire. GetAnodeWireOffset() What is this offset? • In AliTRDdigitizer.cxx: Redistribute positions of el.-cluster according to GARFIELD drift time. Depends on distance to wire

  9. Detector ResponseNon-Isochronity of Drift: Results Angular resolution as function of distance to wire Pulseheight as function of drift time

  10. Detector ResponsePosition Resolution (C. Lippmann)

  11. Detector ResponseResolution as Function of Incidence Angle Resolution for electrons too good in simulations?

  12. Detector ResponseSpace Charge Effects • Space Charge • Detailed simulation with reasonable agreement to data • Could in principle be included in AliRoot detector response • Need to keep track of the history of the incoming charge  time consuming • Parametrization possible?

  13. Detector ResponseTR Simulation: Geant4 Implementation • Problem with current implementation: • Does not describe momentum dependence of pion suppression seen in test beam data • In principle momentum dependent parameter tuning possible • Evaluation of Geant4 • First look: Momentum dependence might be closer to test beam • But complicated to handle • Needs closer investigation + discussion with ATLAS group

  14. Trigger Software • AliRoot implementation of trigger existing (B. Vulpescu) • Local Tracking Unit (LTU) • Global Tracking Unit (GTU) • Own TRIGGER module?

  15. Fast Simulation Input • Investigation by Tariq Mahmoud • Fast simulation framework • Parametrization of tracking (ITS+TPC+TRD) for pions • TRD pion suppression from test beam • Input • Backgound: parametrized HIJING • PHYTIA (CTEQ4L): 115 c/cbar, 5 b/bbar • J/Y, : Generator from AliRoot library, • Open questions • Correlations between pt, , f resolution • principal component analysis? • Parametrizations for electron tracking • g-conversions from p0 decays before ITS (<2% ?)

  16. Fast SimulationPion Suppression by TPC Study different scenarios: 6.9% dEdx-resolution: max. supp. TPC3 1000 TPC4 500 TPC5 100 10% dEdx-resolution: max. supp. TPC6 1000 TPC7 500 TPC8 100 No TPC: TPC0 TRD Proposal TPC1 + TPC2

  17. Fast SimulationResults

  18. Status Summary • Detector response • dEdx under control • Couple of new features in digitization • Ongoing investigation of position/angular resolution • TR simulation: Evaluation of Geant4 • Not yet part of HEAD branch • Development branch to avoid interference with work on reconstruction (Marian) • AliRoot implementation of Trigger existing • Fast simulations • First results available

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