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

ITS Alignment 15/01/2008 Adam Jacholkowski 1

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

(alias – reducing the gap between simulation and REALITY)

HAPPY NEWYEAR !!!

Half-TPC cosmic shower event taken in December test


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


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)


ITS +(TPC) resolutions: example

(after the fixes)

High Pt muonsnot sensitiveto the change ofthe sign: -0.0081+0.0081, butphi shifted (!?)


Same as before but with AliRoot (4.10)(Head of 08/01/08, ROOT v5-17-06)

No phi shift,resolutions slightly betterIP 25 20 μm


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


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 !


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) // [email protected] 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


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…


More details in https://alice.logbook.cern.ch

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

(Accessible only from inside CERN !!!)

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DAQ-ECS Operation@ Point 2

12

SPD Operation in Dec 07 Run

• 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

( 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-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

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

1

10

100

1000

10000

SPD SDD SSD TPC TRD TOF MCH MTR HMP FMD T00 V00 ZDC ACO

Number of standalone runs

Before Cosmic

During Cosmic

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Global Partition during Cosmic Run (1)

0

5

10

15

20

25

30

35

40

1 2 3 4 5 6 7 8 9 10 11 12

Duration (hours)

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

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Global Partition during Cosmic Run (2)

1,0E+00

1,0E+01

1,0E+02

1,0E+03

1,0E+04

1,0E+05

1,0E+06

1,0E+07

1,0E+08

1 2 3 4 5 6 7 8 9 10 11 12

Events

Number of detectors in the global partition(Does NOT include standalone runs)

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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”


Spurious ITS tracks (SA reconstruction)

(from Cvetan collection of ITS reconstructed events)


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’


Lorentz angle residuals (Giuseppe)

electrons

holes


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 !!!


Backup Slides

E8 - new ToE ?

24

Preparation for ITS alignmentPreparation for ITS alignment

A. DaineseA. Dainese(INFN – LNL)(INFN – LNL)

for the ITS alignment group (CERN, LNL, NIKHEF, PD, TS)for the ITS alignment group (CERN, LNL, NIKHEF, PD, TS)

What? What? ITS detectors, target alignment precisionITS detectors, target alignment precision Why? Why? Impact of misalignmentsImpact of misalignments How? How? Strategy and methodsStrategy and methods How well? How well? First results from simulationFirst results from simulation

(ITS slides shown at the 14th December Physics Board)

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ITS detector resolutions & target alignment precisions

Full: initial misalignments as expected from the mechanical imprecision after installation, actually set to 20-45 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 ~0.7resol. ~20% degradation of the resolution

SPD(r = 4 & 7 cm)

SDD(r = 14 & 24 cm)

SSD(r = 39 & 44 cm)

nom. resolutions

xloc (yloc) zloc [m3] 12 (0) 120 38 (0) 20 20 (0) 830

full mis. (shifts)

xlocyloczloc [m3] 20 20 20 45 45 45 30 30 100

residual mis. (shifts)

xlocyloczloc [m3] 10 10 20 20 20 20 15 15 100

rotations (mrad)

around xloc,yloc,zloc 0.3 0.3 0.3

yloc

zloc

xloc

detector local c.s.: xloc~rglob, yloc~rglob, zloc = zglob

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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 / 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:1) start with layers easier to calibrate: SPD and SSD

good resol. in r (12-20m), worse in z (120-830m) ITS z resol. provided by SDD anode coord. (20m) 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

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PARAM SPD RMS SDD RMS SSD RMS

Iter Millep Iter Millep Iter Millep

x (m) 2 5 3 5 5 8

y (m) 7 8 20 16 64 66

z (m) 8 6 3 5 60 64

(mdeg) 17 16 40 21 -- 191

(mdeg) 6 9 8 6 16 26

(mdeg) 58 43 43 26 -- 153

• 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

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Iterative local method:full simul. with misal., iterations

SPD inner: mean, RMS

global

glob

al z

(cm

)

x (m)

A.Rossi

iterationsconvergence

worse on the sides need pp tracks

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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 mangles: ~0.1 mrad

Method (under development):Assume that TPC and ITS are already

internally aligned and calibratedUse independently fitted tracks

in the ITS and the TPCAlignment params are estimated

by a Kalman filter algorithmProof-of-principle test with

“toy” tracks

M. Krzewicki

32

ITS-AMS -The Concept

CCD andSupporting 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) 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)


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 (?!)

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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)

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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

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

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