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ITS story (since the last meeting) from the alignment perspective

ITS story (since the last meeting) from the alignment perspective. (alias – reducing the gap between simulation and REALITY). HAPPY NEW YEAR !!!. 2008. Half-TPC cosmic shower event taken in December test. New v11Hybrid geometry and its (initial) problems.

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ITS story (since the last meeting) from the alignment perspective

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  1. ITS story (since the last meeting)from the alignment perspective (alias – reducing the gap between simulation and REALITY) HAPPY NEWYEAR !!! 2008 Half-TPC cosmic shower event taken in December test Adam Jacholkowski

  2. New v11Hybrid geometry and its (initial) problems • Slight increase of the SPD1 layer radius (?) • SPD2 layer turbo configuration: chirality-inversion • Extra space added for radial misalignments  solution to avoid TGeo overlaps • More details + better estimate of the material budget • Expected a minor degradation of the IP resolutions • New/updated AliITStrackSA.cxx to be used with the v11Hybrid (Andrea D.) • Some bad surprises when starting to use this  dramatic drop of efficiency & precision  bugs Adam Jacholkowski

  3. Some of the bugs/fixes • SIGFPE, arithmetic exception in ApproximateBetheBloch !?? (related to new materials?), Youri’s fix  if(beta2 >=1)return kVeryBig , my fix if(beta2>=0.99999) beta2 = 0.99999 (not enough for electrons !), but WHY it happens ? • Small efficiency in the first quadrant – ladder 3 in SDD1 rotated  in AliITSv11Hybrid.cxx line SetT2Lmatrix(…) replaced by if(c1 !=2) { as before } else {SetT2Lmatrix(……,c2<3)}; // Andrea D. • SPD1 RecPoints shifted radially a small change (Andrea D.) in AliITSv11Hybrid::AddAlignableVolumes() : -0.0081  +0.0081 in SetT2Lmatrix(strENtryName4.Data(),-0.0081,kTRUE, kTRUE) • Tests of simulation + reconstruction (Andrea and me) with the above modifications (zero misalignments)  reasonable results, only minor (albeit non null) degradation of the resolutions as compared to the OLD case • New reader for the raw SPD (Domenico E.) applying TRUE mapping  AliITSRawStreamSPD_NEWGEO.cxx • Updated SSD noise file (Enrico F.) : Run0_9999999_v0_s0.root, could not be used during the test run (OCDB not updated due to a FXS problem) • AliRoot v4-09-Rev-01 OK - presumed to be used for reco (on AliEn) Adam Jacholkowski

  4. ITS +(TPC) resolutions: example (after the fixes) • High Pt muons • not sensitive to the change of the sign: -0.0081 • +0.0081, but phi shifted (!?) Adam Jacholkowski

  5. Same as before but with AliRoot (4.10)(Head of 08/01/08, ROOT v5-17-06) No phi shift, resolutions slightly better IP 25  20 μm Adam Jacholkowski

  6. SPD tracklets as seen with alieve (AliRoot HEAD 30.11.07, v11Hybrid with fixes in sim and reco) Deficit of tracklets, no match with RecPoints  to be clarified Adam Jacholkowski

  7. Cosmic run reconstruction macro (by Andrea D.) - rec_cosmics_onlyITS(…) • Increased tolerances, no cluster de-convolution • Amplitude use switched off (no dE/dx TPC-ITS match) • No virtual clusters in dead zones • Most probable Pt (B = 0 case) set to 0.35 • Easy switch for removing layers from the reconstruction • All other cosmic options (like pseudo-vertex) ON • A BIG hope – this macro to be usable for the data collected during the December mini-cosmic run ! • Working fine on the MC data ! Adam Jacholkowski

  8. rec_cosmics_onlyITS.C void rec_cosmics_onlyITS(Bool_t localRec=kTRUE, Bool_t noSPD=kFALSE, Bool_t noSDD=kFALSE, Bool_t noSSD=kFALSE) { //execute reconstruction for cosmics with ITS alone (for alignment) // andrea.dainese@lnl.infn.it AliITSRecoParam * itsRecoParam = AliITSRecoParam::GetCosmicTestParam(); itsRecoParam->SetClusterErrorsParam(2); itsRecoParam->SetFindV0s(kFALSE); itsRecoParam->SetAddVirtualClustersInDeadZone(kFALSE); itsRecoParam->SetUseAmplitudeInfo(kFALSE); if(noSPD) { itsRecoParam->SetLayerToSkip(0); itsRecoParam->SetLayerToSkip(1); } if(noSDD) { itsRecoParam->SetLayerToSkip(2); itsRecoParam->SetLayerToSkip(3); } if(noSSD) { itsRecoParam->SetLayerToSkip(4); itsRecoParam->SetLayerToSkip(5); } AliITSReconstructor::SetRecoParam(itsRecoParam); // most probable pt, relevant only if B=0 // default is 0.35 [GeV] Double_t mostProbPt=0.35; AliExternalTrackParam::SetMostProbablePt(mostProbPt); //-------------------------------------- AliReconstruction reco; reco.SetOption("ITS","cosmics,onlyITS"); reco.SetWriteESDfriend(kTRUE); reco.SetWriteAlignmentData(kTRUE); if(localRec) { reco.SetRunLocalReconstruction("ITS"); } else { reco.SetRunLocalReconstruction(" "); } reco.SetUseTrackingErrorsForAlignment("ITS"); reco.SetRunTracking("ITS"); reco.SetFillESD("ITS"); reco.SetRunHLTTracking(kFALSE); //--------------------------------------- TStopwatch timer; timer.Start(); reco.Run(); timer.Stop(); timer.Print(); cout<<"reconstruction completed"<<endl; return; Adam Jacholkowski

  9. What has happened during thecosmic run of the 10-21 December • Shortage of the power suppliers  not full detectors could be powered • Global problem of trigger timing (time alignment !)  difficulty to “see” the same events in all the active sub-detectors • SDD (and SPD?) mapping problems needing some ad hoc solutions to get correct RecPoints • High noise in SSD, as forseen, + OCDB problem  hard to find cosmics using ONLY SSD • Poor cosmic trigger (10x20 cm2 scintillator below ALICE), rate ~ 0.05 Hz, as expected for FASTOR, but not all trigger muons crossing the ITS ! • TPC – ITS desperate search of common events… Adam Jacholkowski

  10. More details in https://alice.logbook.cern.ch (Accessible only from inside CERN !!!) • Example – run 15084 (20.12.07, 8:02 – 8:47), potential candidate for events with common TPC – ITS tracks • Run type – PHYSICS • Run duration – 45 mins • Active detectors – SPD, SDD, SSD, TPC, ACORDE* • Number of events – 255 ( = 28 - 1 !) • File size – 3.5 Gb (TPC with zero suppression) • Trigger rate - 0.09 events/s • SHUTTLE status – OK • Available on AliEn Adam Jacholkowski

  11. DAQ-ECS Operation@ Point 2

  12. Vito Manzari PDAS Giorgio Stefanini SPD Operation in Dec 07 Run ( ALICE team meeting 20/12/07) • C-side power on ≈ all half-staves • A-side power on a few half-staves • LV power supply modules still missing • Cooling system circuit completed with connections on miniframe A-side

  13. The Vital Importance of Cooling • Formula 1 cars • engine power ≈ 800 hp ≈ 600 kW • heat loss ≈ same • engine mass ≈ 250 kg • power/mass ratio ≈ 2.4 kW/kg • SPD • power dissipation in the on-detector Si chips ≈ 1.3 kW • total mass of the Si chips ≈ 0.2 kg • power/mass ratio ≈ 6.5 kW/kg

  14. Results from Runs • Half-staves ok pixel matrix, MCMs, cabling • DCS ok • Cooling ok initial problems in plant connections • DAQ stability test ok • Global run ok • Cosmics trigger more work to do

  15. Standalone runs at Point 2 in 2007 • 12 detectors ran standalone before the cosmic run • All the 14 installed detectors during the cosmic run

  16. Global Partition during Cosmic Run (1) • Global partition • Groups of detectors in a global run • Using the Central Trigger Processor • Pulser or cosmic trigger Number of detectors in the global partition(Does NOT include standalone runs)

  17. Global Partition during Cosmic Run (2) Number of detectors in the global partition(Does NOT include standalone runs)

  18. CMS NOTE 2007/xxx December 28, 2007 by CMS Tracker Alignment Team, CMS Tracker Alignment at Integration Facility  “…about 5 M cosmic events were collected with the partially active CMS Tracker” Tracks seen only in TPC (not new) Looking for ITS tracks  messy events (till now)

  19. Spurious ITS tracks (SA reconstruction) (from Cvetan collection of ITS reconstructed events) Adam Jacholkowski

  20. Lorentz angle controversy(Giuseppe – Bjorn) • Example of a general problem of separation of alignment effects from physical / detector effects • Quantification of the effect – see the previous meeting presentation by Giuseppe Bruno • Some doubts raised by Bjorn concerning the relative roles of the holes – electron contribution to the signal • Suggestion to contact RHIC experts who have “measured” this effect in the strips • Note – SPD1 and SPD2 opposite direction of the drift  the effect ‘doubles’ Adam Jacholkowski

  21. Lorentz angle  residuals (Giuseppe) electrons holes Adam Jacholkowski

  22. A temptative TO DO list • Debugging of the v11Hybrid geometry – activating it also in AliEve • Extensive misalignment tests to see robustness against TGeo overlaps (use the overlap checker !) and sensitivity of the resolutions (new misalignment files ?) for v11Hybrid geometry • Clarify the tracklets reconstruction in the new geometry (only AliEve problem ?) • Include and test all the mapping corrections – a must to see the first cosmics in the ITS • Be READY for the February Cosmic RUN !!! Adam Jacholkowski

  23. Backup Slides E8 - new ToE ? Adam Jacholkowski

  24. (ITS slides shown at the 14th December Physics Board) Preparation for ITS alignment • What? ITS detectors, target alignment precision • Why? Impact of misalignments • How? Strategy and methods • How well? First results from simulation A. Dainese (INFN – LNL) for the ITS alignment group (CERN, LNL, NIKHEF, PD, TS)

  25. yloc zloc xloc ITS detector resolutions & target alignment precisions • Full: initial misalignments as expected from the mechanical imprecision after installation, actually set to 20-45 mm at the sensor level, probably higher at the ladder or layer level (~100 mm), more later... • Residual: expected misalignment left after applying the realignment procedure(s). Target ~0.7resol. ~20% degradation of the resolution detector local c.s.: xloc~rfglob, yloc~rglob, zloc = zglob

  26. Introduction of “realistic” misalignment • Why “realistic”? • misalignment should follow hierarchy of hardware structure; each level should be misaligned (and then realigned) • magnitude of initial misalignments should be realistic (input from hardware experts) • misalignments at the same hierarchical level should be correlated • E.g., for SPD: barrel / half-barrel / sector / half-stave / ladder # sensitive volumes: 240 / 120 / 24 / 2 / 1 magnitude of misal. (mm):<1000 / ~100 / ~100 / 10-50 / 5 (up to now only the ladder was misaligned) • Transition to realistic misalignment is in progress (requires changes to the ITS geometry) • Will provide: • better playground for preparation of realignment procedures • better estimate of effects of residual misalignments on performance

  27. ITS alignment with tracks:general strategy • Data sets: cosmics + first pp collisions (and beam gas) • use cocktail of tracks from cosmics and pp to cover full detector surface and to maximize correlations among volumes • Start with B off, then switch on B  possibility to select high-momentum (no multiple scattering) tracks for alignment • General strategy: • start with layers easier to calibrate: SPD and SSD • good resol. in rf (12-20mm), worse in z (120-830mm) • ITS z resol. provided by SDD anode coord. (20mm)  easily calibrated  can be included from the beginning in alignment chain • global ITS alignment relative to TPC (already internally aligned) • finally, inclusion of SDD (drift coord: rf), which probably need longer calibration (interplay between alignment and calibration) • Two independent track-based alignment methods in preparation: • global: Millepede 1 (ported to ALICE for muon arm alignment) • local: iterative method based on residuals minimization

  28. Millepede: fast vs. full simulation • Deterioration of results with full detector simulation • This triggered investigations on the different steps of the simulation, with misalignment  found problems with overlaps that caused shift of ITS rec. points  will be solved in new ITS geometry • For the moment, continue alignment studies without misalignments

  29. Iterative local method: full simul., no misal. • about 5 weeks of cosmics, B=0 • no iterations (not necessary without misalignment) M.Lunardon, S.Moretto - Millep A.Rossi – IterLocMeth

  30. Iterative local method:full simul. with misal., iterations SPD inner: mean, RMS iterationsconvergence Dx (mm) global z (cm) global f worse on the sides  need pp tracks A.Rossi

  31. ITS-TPC relative alignment • Relative alignment of ITS and TPC (3 shifts + 3 angles) with straight tracks (including cosmics) • Alignment requirements: given by TPC resolutions: • shifts: ~100 mm • angles: ~0.1 mrad • Method (under development): • Assume that TPC and ITS are already internally aligned and calibrated • Use independently fitted tracks in the ITS and the TPC • Alignment params are estimated by a Kalman filter algorithm • Proof-of-principle test with “toy” tracks M. Krzewicki

  32. TPC End Plate Spherical Mirror Outgoing and Returning Beams CCD and Supporting Electronics SSD Cone (B. Nilsen & D. Truesdale) ITS-AMS -The Concept Four spherical mirrors placed on the ITS reflect collimated laser beams onto a CCD imager. As the focal point of the mirror coincides with the CCD’s linear distance, any movement of the mirror is translated exactly to the image on the CCD. Movement of the images on all four cameras are read out and the motion of the ITS is computed. Three translational and three angular degrees of freedom can be measured with only three cameras. D. Truesdale & B. Nilsen

  33. (ITS) Summary • The ITS alignment challenge: determine 13,000 parameters with a precision of ~10 mm • Track-based alignment using cosmics and pp collisions • preparation for cosmics reconstruction in ITS • Two independent algorithms under development/tests • Millepede (global) • local iterative method (AliALignmentTracks) • Promising results even with cosmics only, should be much better when combining cosmics + pp tracks • ITS alignment relative to TPC also under study – hardware (ITS-AMS) and software (Kalman) Adam Jacholkowski

  34. Open problems and proposed solutions • Geometry overlaps limiting range of misalignments  temporary Fast Simulation solution, long range solution – new v11Hybrid geometry • Cosmics - bad behaviour for “tangent” tracks angle cut limiting range of align-able modules • Hierarchical misalignment ok but realignment not yet adapted  need of some software developments (manpower !) • AliAlignObjCovMatrix exists but not yet fully exploited (in tracking and re-alignment) • No clear strategy yet how to treat “weak misalignment” modes, monitoring/diagnostic tools just starting • Potential problems: offline-online geometry and mapping, t0 drift time (TPC, SDD), common TPC - ITS cosmics (?!) Adam Jacholkowski

  35. Final Conclusion Generally ALICE ready for first cosmics but ITS Alignment is (still) a big CHALLENGE – separation of calibration and simulation/reconstruction arte-facts from purely geometrical effects !!! (partially true also for the TPC)

  36. Fast Simulation • A muon direction is generated • Intersection points with misaligned detectors are evaluated in local coordinate systems • large misal. order of 100 mm • Points smeared with given resolutions • Use tracks with 4-12 points • Advantages w.r.t. standard sim: • clean situation, without simulation/reconstruction effects • faster

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