ST Alignment Validation M. Needham EPFL
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Transcript of ST Alignment Validation M. Needham EPFL
ST Alignment ValidationM. Needham
EPFL
IntroductionDetailed comparision of alignment databases
• October TED Overlaps: magnet on/ magnet off alignment
• Residuals November TED/ Beam off: magnet on/off alignment
• Residuals Long tracks magnet on: magnet on/off alignment
• IT Error tuning
Definitions + Databases:Magnet off: head-20100119Magnet on: slice VeloOTTxTyModulesTxITTxTyRzTTModulesTxRz20100119.dbmagnet on++: magnet on + IT ladder alignment TxRz (with health warning) VeloOTTxTyModulesTxITTxTyRzLaddersTxRzTTModulesTxRz20100122.db
IntroductionDatasets:
Magnet off: November TED, all Collision data with magnet off (including data with VELO moving) Magnet on: 63801, 63806, 63807, 63807, 63809, 63811, 63815, 63849
Magnet on selection cuts
The ST selection: p > 6 GeV, 2/dof < 7
Overlaps• Take Wouters database, transform to October TED and look at overlaps
• Pros: Large high quality dataset that is well understood
• Cons: October to December is a long time, IT + OT opened in October
Box T1 T2
B -800 -1025
A -800 -1042
T None -60
C None -80
Transformation October- November
• Based on studies November TED
• ‘pre-alignment’ in x only
• Quality: dominated by systematics
• Uncertainty: 50 microns ?
OverlapsOverlaps in y decrease with z(beampipe hole bigger)T1: 19 mmT2: 12 mmT3: 5 mm
A-Side C-Side
Top
Bottom
1 mm
1 mm
3 mm
5 mmIT3
No physical overlap IT3C and IT3 Bottom
Survey + correctionfor OT closing, boxAlignment changes by ~ mm
Other stations similarshifts
A-Side Overlaps
T1 T2 T3
B1 B2
A-Side OverlapsOverlap to Residual Magnet
on/ mmResidual Magnet off/mm
Bottom1 -0.17 0.05
Bottom2 0.17 0.09
Top1 0.2 0.1
Top2 0.45 0.32
Top3 0.6 0.43
C-Side Overlaps
T1
B1
T2 T3
Bias’s : 100- 200 micron level
Better than anything we saw before….
Large biases but comparing October TED
with December beam running and including
constrainsts from VELO + OT
C-Side OverlapsOverlap to Residual Magnet
on/ mmResidual Magnet off/mm
Bottom1 -0.32 -0.19
Top1 0.690 0.12
Top2 0.02 0.02
Top3 -0.46 -0.12
Overlap Summary• Magnet off data has biases of 200 microns in TED overlaps
• Magnet on data has larger biases
• But the movements are all at the 200 micron level [apart from Top T1] compared to magnet off
• Constants are not so inconsistant magnet off/on
• Pick one false minimum magnet off, another magnet on ?
Look at residuals in T2
• Dataset: November TED + magnet off
• Databases: magnet on , magnet off
Box Magnet on/mm Magnet off/mm
Top -0.03 -0.02
Bottom -0.02 -0.01
C-side 0.09 -0.01
A-side -0.15 -0.03
T1 T2 T3
dx
Differences magnet on/off at 100 micron level
x Residuals Test
Residual Biases: Tracks
Bias @ 15micron level
Magnet-off dataMagnet off alignment
Magnet-off dataMagnet on alignment Bias @ 18
micron level
IT1
IT2
IT3
A C
Residual Biases: Tracks
RMS 85 mMagnet-off dataMagnet on++ alignment
But this database is good for magnet on
Magnet++Magnetoff
Unbiased residualalso degrades
Residual Biases: Tracks
RMS 62 mMagnet-on dataMagnet on alignment
RMS 64 mMagnet-on dataMagnet off alignment
Residual Biases: Tracks
RMS 15 m
Magnet-on dataMagnet on++ alignment
• Looks good and unbiased residual width improves by ~ 30 %
• But this database is very bad for magnet off
Magnet++Magnet
Unbiased residual
Future StrategyFinding the correct minimum is not trivial
• Is there a real difference magnet off/on ?
Get back to what we did on the MC, what we learnt was good with TED
• Tune clusters errors [next slide]
• Combining datasets [Wouter]
• Track selection
• Evolving cut and strong isolation criteria as in TED/MC studies
• Momentum cut
IT Error TuningAs in the TED, tune unbiased residuals for 1, 2, 3 ,4 strip clusters
• Reasonable track selection: 2/dof < 7, p > 20 GeV
• Assume 1 strip has a binary contribution
• Unfolding this gives the misalignment / multiple scattering
• Unfold this from the 2,3,4 cluster unbiased residualCluster Size Unbiased
residual/mmMC value/pitch Data tune/pitch
1 77 0.19 0.29
2 68 0.12 0.22
3 87 0.17 0.35
4 No Statistics 0.04 put 0.35 ?
itClusterPosition = STOfflinePosition('ToolSvc.ITClusterPosition')itClusterPosition.ErrorVec = [0.28, 0.22, 0.35. 0.35]itClusterPosition.APE = 0.1
Early data tune:
Summary• Getting the IT boxes inter-aligned is tough
• Best database: good to 100 micron
• Databases with magnet off/on differ
• Differences @ the level of 100 -200 micron
• But general trend is reasonably same ?
• Magnet++ is different
• Fixes magnet on by LARGE movements of ladders at price of worse magnet off
Backup
Go to TT
A-Side C-Side
Project to TT
Better than Anything I have seen
Go to TTIT Track Type Residual/mm (Beam) Residual/mm (Oct)
A-side 0.3 0.6
Bottom -0.4 0
C-side -0.3 -0.8
Top -0.2 -0.7
Compare residuals extrapolating IT tracks to TT in TED + beam data
Again discrepancies at the level of hundreds of microns
Can partially be explained by different illumination [at least in Bottom case]
Go to TT
Examine the badGuy in TTaX
TED dataIt’s a rotation
Propagate IT generic tracks to TT
Beam smaller y ]
-5 mrad inLocal frame
Go to TT-0.93 -1.02 -0.52
0.24 -1.88 -0.35
-0.84 -0.84 -0.52
0.1 -0.7 -0.3
-0.79 -0.76 -0.43
0.2 -0.62 0.0
-0.73 -1.16 -0.61
0.12 0.87 -0.08
x
TTaX
TTaU
TTbV
TTbX
Columns:TTa 7, 8, 9TTb 8, 9, 10
TEDdata
Bad luck
Go to TT• Bottom is consistant with Velo-TT studies of C. Salzmann
• Very good cross-check !
• Top: Seems to be global offset. Coming from IT alignment ?
• Subtracting offset my results consistant with C. Salzmann
Comments• Inner Tracker consists of four loosely coupled systems
• Lightweight frames+ boxes: twisting + distortions (ie rotations) important
• Inter-alignment is a challenge: seen already June TED
• Clear we did not take enough magnet off data (especially with Velo not moving)
• But on the otherhand, we have many good things
• A reasonable survey
• Varied track sample: beam-gas, collisions, halo tracks, ….
• Can use November TED simulataneously
• Easy to use large October TED as cross-check (good to see IT overlaps)
Comments• Thinking ahead…
• Many of these advantages we lose if the detector is opened
• OT is already opened. Movements of IT at 50 micron level
CommentsEnsure complementary + cross-checks @ same level as 2009
• Survey: what survey is needed, what is possible ?
• TED data: ~ 50 shots to allow pre-alignment/cross-checks
• Similar mix of beam-gas as 2009 ?
Improve on 2009
• Larger sample with magnet off (100k ?) to see IT overlaps clearly
• Anything else ? in TAE mode beam2 gas, displaced bunch collisions…
• Magnet off: give me the hits of particles from anywhere I will give you the tracks
October TED presented in December
October TED presented in December
Residual Biases: Tracks
RMS 41 m ~ 18 m
Magnet-on dataMagnet on alignment
RMS 42 m ~ 21 m
Magnet-on dataMagnet on alignment
T-tracks