ITS Alignment 15/01/2008 Adam Jacholkowski1 ITS story (since the last meeting) from the alignment perspective (alias – reducing the gap between simulation and REALITY) HAPPY NEW YEAR !!! Half-TPC cosmic shower event taken in December test

ITS Alignment 15/01/2008 Adam Jacholkowski2 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

ITS Alignment 15/01/2008 Adam Jacholkowski3 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>= ) beta2 = (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() :  in SetT2Lmatrix(strENtryName4.Data(), ,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_ _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)

ITS Alignment 15/01/2008 Adam Jacholkowski4 ITS +(TPC) resolutions: example (after the fixes) High Pt muons not sensitive to the change of the sign:  , but phi shifted (!?)

ITS Alignment 15/01/2008 Adam Jacholkowski5 Same as before but with AliRoot (4.10) (Head of 08/01/08, ROOT v ) No phi shift, resolutions slightly better IP 25  20 μm

ITS Alignment 15/01/2008 Adam Jacholkowski6 SPD tracklets as seen with alieve (AliRoot HEAD , v11Hybrid with fixes in sim and reco) Deficit of tracklets, no match with RecPoints  to be clarified

ITS Alignment 15/01/2008 Adam Jacholkowski7 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 !

ITS Alignment 15/01/2008 Adam Jacholkowski8 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) // 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(mostPr obPt ); // 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; rec_cosmics_onlyITS.C

ITS Alignment 15/01/2008 Adam Jacholkowski9 What has happened during the cosmic run of the 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…

ITS Alignment 15/01/2008 Adam Jacholkowski10 More details in Example – run ( , 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 ( = !)  File size – 3.5 Gb (TPC with zero suppression)  Trigger rate events/s  SHUTTLE status – OK  Available on AliEn (Accessible only from inside CERN !!!)

11 DAQ-ECS Point 2

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

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-stavesokpixel matrix, MCMs, cabling DCSok Coolingokinitial problems in plant connections DAQ stability testok Global runok Cosmics triggermore work to do

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

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

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

18 Tracks seen only in TPC (not new) Looking for ITS tracks  messy events (till now) 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”

ITS Alignment 15/01/2008 Adam Jacholkowski19 Spurious ITS tracks (SA reconstruction) (from Cvetan collection of ITS reconstructed events)

ITS Alignment 15/01/2008 Adam Jacholkowski20 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’

ITS Alignment 15/01/2008 Adam Jacholkowski21 Lorentz angle  residuals (Giuseppe) electrons holes

ITS Alignment 15/01/2008 Adam Jacholkowski22 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 !!!

ITS Alignment 15/01/2008 Adam Jacholkowski23 Backup Slides E 8 - new ToE ?

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

25 ITS detector resolutions & target alignment precisions Full: initial misalignments as expected from the mechanical imprecision after installation, actually set to  m at the sensor level, probably higher at the ladder or layer level (~100  m), more later... Residual: expected misalignment left after applying the realignment procedure(s). Target ~0.7  resol.  ~20% degradation of the resolution SPD (r = 4 & 7 cm) SDD (r = 14 & 24 cm) SSD (r = 39 & 44 cm) nom. resolutions x loc  (y loc )  z loc [  m 3 ] 12  (0)   (0)  2020  (0)  830 full mis. (shifts) x loc  y loc  z loc [  m 3 ] 20  20  2045  45  4530  30  100 residual mis. (shifts) x loc  y loc  z loc [  m 3 ] 10  10  2020  20  2015  15  100 rotations (mrad) around x loc,y loc,z loc 0.3 y loc z loc x loc detector local c.s.: x loc ~r  glob, y loc ~r glob, z loc = z glob

26 Introduction of “realistic” misalignment Why “realistic”? 1.misalignment should follow hierarchy of hardware structure; each level should be misaligned (and then realigned) 2.magnitude of initial misalignments should be realistic (input from hardware experts) 3.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. (  m): <1000 / ~100 / ~100 / / 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: 1)start with layers easier to calibrate: SPD and SSD  good resol. in r  (12-20  m), worse in z (  m)  ITS z resol. provided by SDD anode coord. (20  m)  easily calibrated  can be included from the beginning in alignment chain 2)global ITS alignment relative to TPC (already internally aligned) 3)finally, inclusion of SDD (drift coord: r  ), 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 PARAM SPD RMSSDD RMSSSD RMS IterMillepIterMillepIterMillep x (  m) y (  m) z (  m)  (mdeg)  (mdeg)  (mdeg) about 5 weeks of cosmics, B=0 no iterations (not necessary without misalignment) Iterative local method: full simul., no misal. A.Rossi – IterLocMethM.Lunardon, S.Moretto - Millep

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

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  m 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 ITS-AMS -The Concept CCD and Supporting Electronics TPC End Plate Spherical Mirror SSD Cone Outgoing and Returning Beams 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 (B. Nilsen & D. Truesdale)

ITS Alignment 15/01/2008 Adam Jacholkowski33 (ITS) Summary The ITS alignment challenge: determine 13,000 parameters with a precision of ~10  m 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)

ITS Alignment 15/01/2008 Adam Jacholkowski34 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 (?!)

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 1.A muon direction is generated 2.Intersection points with misaligned detectors are evaluated in local coordinate systems large misal. order of 100  m 3.Points smeared with given resolutions 4.Use tracks with 4-12 points Advantages w.r.t. standard sim: clean situation, without simulation/reconstruction effects faster Fast Simulation