T-Station Alignment T-Station Alignment Infrastructure at LHCbInfrastructure at LHCb

AdlAdlèène Hicheurne Hicheur(Ecole Polytechnique Fédérale de Lausanne)(Ecole Polytechnique Fédérale de Lausanne)

T-Station Alignment group: J.Blouw, F.Maciuc, M. Deissenroth, A. PerieanuT-Station Alignment group: J.Blouw, F.Maciuc, M. Deissenroth, A. Perieanu (Heidelberg), A.Hicheur, L.Nicolas (EPFL), G.Raven, J.Amoraal, I.Nardulli (NIKHEF)(Heidelberg), A.Hicheur, L.Nicolas (EPFL), G.Raven, J.Amoraal, I.Nardulli (NIKHEF)

LHC Alignment Workshop, 4-6/09/2006LHC Alignment Workshop, 4-6/09/2006

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OutlineOutline

• IntroductionIntroduction– Vertexing and tracking subsystemsVertexing and tracking subsystems– T stationsT stations

• Alignment framework: global viewAlignment framework: global view

• Geometry and alignable unitsGeometry and alignable units

• Tracking model and toolsTracking model and tools

• Solving toolsSolving tools

• Conclusion and outlookConclusion and outlook

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VVeeLLoo

TTrigger rigger TTrackerracker

T StationsT StationsIInner nner TTracker (Si)racker (Si)OOuter uter TTracker (straws)racker (straws)

Vertexing and tracking in Vertexing and tracking in LHCbLHCb

In fringe field of magnetFast track momentum measurement for trigger

dP/P ~ 30% (PT=3GeV)Offline reconstruction of long-lived and low momentum particles

Vertex Vertex reco.reco.

““Full” momentum measurementFull” momentum measurement

Target resolution Target resolution dP/P ~ 0.35-dP/P ~ 0.35-0.55% 0.55%

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T stationsT stations

TT Station

Inner tracker

Outer Tracker

Inner Inner TrackerTracker

Outer TrackerOuter Tracker

High track density regionHigh track density region

Silicon strip detectorSilicon strip detectorPitch 198 Pitch 198 μmμm, implant , implant width 50 width 50 μmμm

2% of acceptance, 20% 2% of acceptance, 20% of tracksof tracks

Maximum occupancy Maximum occupancy 2.3%2.3%

Each station has four Each station has four boxesboxes

Total: 336 ladders to alignTotal: 336 ladders to align

• 5 mm Kapton/Al straw tubes 5 mm Kapton/Al straw tubes (longest straws 4.7m)(longest straws 4.7m)• Drift gas 70:30 Ar:CO2 Drift gas 70:30 Ar:CO2 mixturemixture• (14+8)*4*3 = 264 modules to (14+8)*4*3 = 264 modules to alignalign

3 Stations with 4 layers, x type and 3 Stations with 4 layers, x type and stereo u,v type ( 0stereo u,v type ( 0oo, -5, -5oo, 5, 5oo, 0, 0oo))

Degradation: for x misalign of 0.5 mm, Degradation: for x misalign of 0.5 mm, although trk efficiency not much affected, although trk efficiency not much affected, p/p ~ 10-15%p/p ~ 10-15%

(25% for 1mm)(25% for 1mm)

IT Initial positioning (meas. + IT Initial positioning (meas. + estimates)estimates)

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Alignment frameworkAlignment framework

Upstream processingUpstream processing(tracking algs, etc…)(tracking algs, etc…)

AlignToolsAlignTools

Align Data objectsAlign Data objects

Align AlgorithmsAlign Algorithms

Stores/DBsStores/DBs

Transient event storeTransient event store

Transient detector storeTransient detector store

Conditions DBConditions DBSolvingSolvingTrack Track

SelectionSelection

Track ModelTrack Model

UpdatUpdatee

Book-keeping Book-keeping of alignable of alignable geometrygeometry

etc…etc…

Tracking infoTracking info

Geometry infoGeometry info

iterate

LHCb Brunel LHCb Brunel environmentenvironment

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Geometry and granularityGeometry and granularityOOTTITIT

Inside IT box:Inside IT box:

4 ladder layers: 2 4 ladder layers: 2 layers mounted on layers mounted on each cooling rod.each cooling rod.

coolingcooling

Straws grouped in double Straws grouped in double layered moduleslayered modules

4 module layers per station4 module layers per station

Overlaps:Overlaps:

IT ladders overlap IT ladders overlap across the stripsacross the strips

Overlaps between IT Overlaps between IT boxesboxes

Small overlap between Small overlap between IT and OTIT and OT

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Tracking model and toolsTracking model and toolsVelo tracks

Forward tracksForward tracks

Matched tracks

VTT tracks

T TT tracks For T station internal For T station internal alignment, use ofalignment, use of T seedsT seeds

- Because of fringe field, - Because of fringe field, cannot take a purely linear cannot take a purely linear model (e.g polynomial model (e.g polynomial parameterization). Momentum parameterization). Momentum estimate from pt kick in the estimate from pt kick in the magnetmagnet

- Trajectory tool (both for - Trajectory tool (both for tracks and measurements) to tracks and measurements) to be used for derivatives, be used for derivatives, defining misalignments, etc…defining misalignments, etc…

- For selection, main challenge - For selection, main challenge is to reject ghost tracks, select is to reject ghost tracks, select isolated tracksisolated tracks

Seed tracksSeed tracks

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Solving alignmentSolving alignment• Splitted between processing Splitted between processing

(i.e accumulate statistics) and (i.e accumulate statistics) and solvingsolving

• IT ladders and OT modules IT ladders and OT modules treated in a similar waytreated in a similar way

• Processing part meant to run in Processing part meant to run in different ways: direct use of different ways: direct use of Millepede, global minimization, Millepede, global minimization, etc…etc…

• Final solving part separated Final solving part separated from the processing partfrom the processing part– On call methods implementing On call methods implementing

different approaches (singular-different approaches (singular-friendly inversion as embedded friendly inversion as embedded in Millepede, diagonalization, in Millepede, diagonalization, MINRES algorithm)MINRES algorithm)

• Steps:Steps:– Align IT and OT internallyAlign IT and OT internally– Use “hybrid” tracks and Use “hybrid” tracks and

overlaps to align IT wrt OToverlaps to align IT wrt OT

uu

vv

ww

Measurement, Measurement, stereostereo

u = x cos(u = x cos() + y sin() + y sin())

iimeas

ii

trkmeasxx

2

2

tracktrack

Hit strip/wireHit strip/wire

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Early studiesEarly studies• Note: the studies have been done with simplified Note: the studies have been done with simplified

set-ups, neglecting many effects (sensor thickness, set-ups, neglecting many effects (sensor thickness, multiple scattering, etc…)multiple scattering, etc…)

• Done only for two degrees of freedom (translations Done only for two degrees of freedom (translations in the plane perpendicular to the beam axis) + in the plane perpendicular to the beam axis) + straight tracksstraight tracks– Non linearities not taken into accountNon linearities not taken into account

• With all the detector effects, the hope is to achieve:With all the detector effects, the hope is to achieve:– IT: 10 IT: 10 m precision for the coordinate across the strips (x) m precision for the coordinate across the strips (x)

and about an order of magnitude worse in yand about an order of magnitude worse in y– OT: ~ 50 OT: ~ 50 m precision across the straws (x)m precision across the straws (x)

• Currently:Currently:– Rotations and z translation being studiedRotations and z translation being studied– Modeling of non-linearities under investigationModeling of non-linearities under investigation

• Iterations machinery to be trained furtherIterations machinery to be trained further

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Conclusion and outlookConclusion and outlook• T-Station Alignment strategy definedT-Station Alignment strategy defined

– Implementation of core software on-goingImplementation of core software on-going• Feasibility studies performedFeasibility studies performed

– Despite the naïve simulation, important items Despite the naïve simulation, important items figured out already: treatment of non-linearities, figured out already: treatment of non-linearities, handling iterations,…handling iterations,…

• The plan is to have a complete SW The plan is to have a complete SW framework by the end of the yearframework by the end of the year

• Event samples for the algorithmsEvent samples for the algorithms– Simulated minimum bias and inclusive b eventsSimulated minimum bias and inclusive b events– Before “proper collision” data, beam-gas and Before “proper collision” data, beam-gas and

beam-halo tracks to be considered (no cosmics beam-halo tracks to be considered (no cosmics like other experiments)like other experiments)

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Back upBack up

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Bridge frame (stainless steel)Bridge frame (stainless steel)

Shorter framesShorter frames

Longer framesLonger frames

Supports:Supports:12 Outer tracker ¼ stations12 Outer tracker ¼ stations6 Inner tracker ½ stations6 Inner tracker ½ stations

Rail tolerances:Rail tolerances:

Flatness: 3 mmFlatness: 3 mm

Straightness: Straightness: 2mm2mm

(over 6.55 m)(over 6.55 m)

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Support structures for the Support structures for the trackerstrackers

IT support frameIT support frame

OT C-OT C-frameframe

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C-frame detailsC-frame details

Holes for servicesHoles for services

2 verticalPlatesCombined With 2 stripsFor torsionstiffness

RASNIK alignment RASNIK alignment holesholes

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More on OTMore on OT

Single Double Layer

5mm straws

pitch 5.25 mm

Tracke- e

-e-

e-e

-

r (mm)r (mm)

Dri

ft t

ime

(ns)

Dri

ft t

ime

(ns)

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Pulls for IT align param x and z Pulls for IT align param x and z (toy MC study)(toy MC study)

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Pt derivation from Velo tracksPt derivation from Velo tracks

Slide from J.Albrecht