alignment of muon chambers with tracks file1 overview of the atlas muon spectrometer alignment 2...

Alignment of muon chambers with tracks

Sergey Kotov, Jens Schmaler, Oliver Kortner

MPI für Physik, Munich

ATLAS-D workshop, Heidelberg, 22.09.2006

Sergey Kotov, Jens Schmaler, Oliver Kortner (MPI für Physik, Munich) Alignment of muon chambers with tracks ATLAS-D workshop, Heidelberg, 22.09.2006 1 / 18

1 Overview of the ATLAS Muon Spectrometer alignment

2 Track based alignment of chambers without optical sensors

3 Current performance of track based alignment algorithm

4 A segment based approach to the muon spectrometer alignment

5 Conclusions and plans


Overview of the ATLAS Muon Spectrometer alignment

Momentum measurement design goal:δpt/pt = 10% for 1 TeV muons⇒sagitta of 500 µm measured with 50 µm accuracy

Muon chambers (∼ 1200 in total) are high-precisionobjects by construction: sense wires are placedwith 20 µm precision during chamber assembly

Single muon chamber spatial resolution is ∼ 40µm⇒ muon chambers must be aligned to 30 µmaccuracy in order to provide the requiredmomentum resolution

In the first order, only the relative alignment of triplets of chambers (towers) traversed by thesame muon track is important for momentum measurementOptical alignment system provide this tower alignment:

I in the barrel region 3-point straightness monitors (RASNIKs) installed on the inner/middle/outerchambers form projective lines pointing to the interaction region

I in the endcap regions projective lines are impossible because the cryostats of endcap toroid magnetsblock the interaction region⇒ the endcap alignment relies on high precision reference rulers –alignment bars which form alignment grid for the endcaps

In principle, muon tracks can be used to align the muon spectrometer (some of theseactivities are being pursued by MPI MDT group)


Track based alignment of chambers without projective alignment sensors

Many muon chambers don’t have projectiveoptical alignment sensors⇒ no correction tosagitta measurement

I small barrel chambersI BEE chambersI BIS8 chambers

Solution: use muon tracks passing throughoverlaps between these chambers andoptically aligned chambers to obtain theirrelative positions

Alignment of chambers without opticalprojective sensors is official respons-ibility of MPI MDT group and duringdata taking will be carried out atMunich MDT calibration and alignmentcenter (part of Munich Tier-2)


ATHENA track based alignment package

ATHENA

Optical alignment

and calibration

constants

Muoncalibration

data stream

Preselectorof tracks with

overlaps(trigger info)

Muon track

reconstruction

TrackSegmentswith associatedRIOs_OnTrack

Trackswith associatedRIOs_OnTrack

Alignmentwith segments

algorithm

Alignmentwith RIOs_OnTrack

algorithm

Tracking"pseudo"sensors

data

ASAP/ARAMyS

An ATHENA package MuonTrkAlign for track based alignment of the muon spectrometer is beingdeveloped by MPI MDT group

based on new common tracking EDM (uses its data objects and tools):I operate with tracking EDM data objects: Tracks, TrackParameters, RIO_OnTrackI use TrackFitters, TrackExtrapolators and other common tracking toolsI runs on both Mounboy and MOORe output

current results were obtained with:I release 12.0.1, samples of 20 GeV and 100 GeV muonsI perfectly aligned detector geometryI input track container “ConvertedMooreTracks”


Check of common tracking tools: MDT residuals for refitted 20 GeV tracks

[mm]fit-RmeasR-1 -0.8 -0.6 -0.4 -0.2 -0 0.2 0.4 0.6 0.8 10

2000

4000

6000

8000mµ>=2.8 ∆<mµ=86.8 ∆σ

Large chambers track

[mm]fit-RmeasR-1 -0.8 -0.6 -0.4 -0.2 -0 0.2 0.4 0.6 0.8 10

200

400

600 mµ>=3.9 ∆<mµ=54.3 ∆σ

Small inner chamber track

[mm]fit-RmeasR-1 -0.8 -0.6 -0.4 -0.2 -0 0.2 0.4 0.6 0.8 10

200

400

600 mµ>=0.7 ∆<mµ=50.4 ∆σ

Small middle chamber track

[mm]fit-RmeasR-1 -0.8 -0.6 -0.4 -0.2 -0 0.2 0.4 0.6 0.8 10

200

400

600

800 mµ>=-2.2 ∆<mµ=37.1 ∆σ

Small outer chamber track


Check of common tracking tools: position at MS entrance for refitted tracks

x0 [mm]∆-6 -4 -2 0 2 4 60

50

100

150

200 mµ>=20 ∆<mµ=310 ∆σ

OrigTrkRefit-OrigTrk

y0 [mm]∆-6 -4 -2 0 2 4 60

50

100

150

200 mµ>=13 ∆<mµ=294 ∆σ


z0 [mm]∆-1 -0.8 -0.6 -0.4 -0.2 -0 0.2 0.4 0.6 0.8 10

50

100

150

200

mµ>=-2 ∆<mµ=51 ∆σ


x0 [mm]∆-6 -4 -2 0 2 4 60

50

100

150mµ>=25 ∆<mµ=351 ∆σ

LrgChmTrk-OrigTrk

y0 [mm]∆-6 -4 -2 0 2 4 60

50

100

150 mµ>=7 ∆<mµ=298 ∆σ

LrgChmTrk-OrigTrk

z0 [mm]∆-1 -0.8 -0.6 -0.4 -0.2 -0 0.2 0.4 0.6 0.8 10

50

100

150 mµ>=-1 ∆<mµ=48 ∆σ

LrgChmTrk-OrigTrk


Check of common tracking tools: momentum at MS entrance for refitted tracks

[rad]φ∆-0.005-0.004-0.003-0.002-0.001 0 0.0010.0020.0030.0040.0050

50

100

radµ>=-5 ∆<radµ=387 ∆σ


[rad]θ∆-0.0015 -0.001 -0.0005 0 0.0005 0.001 0.00150

50

100

150radµ>=-6 ∆<radµ=186 ∆σ


T/p

Tp∆

-0.2 -0.15 -0.1 -0.05 -0 0.05 0.1 0.15 0.20

100

200

300

>=-0.2 ∆<=1.2 ∆σ


[rad]φ∆-0.005-0.004-0.003-0.002-0.001 0 0.0010.0020.0030.0040.0050

50

100 radµ>=-2 ∆<radµ=372 ∆σ

LrgChmTrk-OrigTrk

[rad]θ∆-0.0015 -0.001 -0.0005 0 0.0005 0.001 0.00150

50

100

150 radµ>=-6 ∆<radµ=188 ∆σ

LrgChmTrk-OrigTrk

T/p

Tp∆

-0.2 -0.15 -0.1 -0.05 -0 0.05 0.1 0.15 0.20

100

200

300>=-0.2 ∆<=1.2 ∆σ

LrgChmTrk-OrigTrk


Extrapolation of large chambers track into small chambers: positions

X0 [mm]∆-150 -100 -50 0 50 100 1500

10

20

30

40>=-2.9 mm∆<=13.3 mm∆σ

Small inner chamber

X0 [mm]∆-150 -100 -50 0 50 100 1500

20

40

60

80

>=1.2 mm∆<=7.3 mm∆σ

Small middle chamber

X0 [mm]∆-150 -100 -50 0 50 100 1500

5

10

15>=-2.0 mm∆<=12.9 mm∆σ

Small outer chamber

Y0 [mm]∆-150 -100 -50 0 50 100 1500

10

20

30

40 >=-1.2 mm∆<=10.5 mm∆σ

Small inner chamber

Y0 [mm]∆-150 -100 -50 0 50 100 1500

20

40

60

80>=0.3 mm∆<=6.1 mm∆σ


Y0 [mm]∆-150 -100 -50 0 50 100 1500

5

10

15

20 >=-0.0 mm∆<=13.5 mm∆σ

Small outer chamber

Z0 [mm]∆-25 -20 -15 -10 -5 0 5 10 15 20 250

5

10

15

20>=0.2 mm∆<=3.3 mm∆σ

Small inner chamber

Z0 [mm]∆-25 -20 -15 -10 -5 0 5 10 15 20 250

20

40

>=0.1 mm∆<=0.9 mm∆σ


Z0 [mm]∆-25 -20 -15 -10 -5 0 5 10 15 20 250

5

10

15

>=0.1 mm∆<=2.0 mm∆σ

Small outer chamber


Extrapolation of large chambers track into small chambers: angles

[rad]φ∆-1 -0.8 -0.6 -0.4 -0.2 -0 0.2 0.4 0.6 0.8 10

10

20

30

>=13.5 mrad∆<=161 mrad∆σ

Small inner chamber

[rad]φ∆-1 -0.8 -0.6 -0.4 -0.2 -0 0.2 0.4 0.6 0.8 10

50

100 >=-0.1 mrad∆<=32 mrad∆σ


[rad]φ∆-1 -0.8 -0.6 -0.4 -0.2 -0 0.2 0.4 0.6 0.8 10

10

20

>=-0.6 mrad∆<=150 mrad∆σ

Small outer chamber

[rad]θ∆-0.1 -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.10

20

40

>=0.5 mrad∆<=8.8 mrad∆σ

Small inner chamber

[rad]θ∆-0.1 -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.10

50

100>=0.3 mrad∆<=5.5 mrad∆σ


[rad]θ∆-0.1 -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.10

10

20

30

40 >=0.6 mrad∆<=6.8 mrad∆σ

Small outer chamber


Problems with extrapolation of large chambers track

Refitting of muon track with new common tracking tools seems to work quite well:

MDT fit residuals are about 50 µm which corresponds to chamber spatial resolution

differences in track perigee parameters between original and refitted tracks at MS entrancelook reasonable

But extrapolation of large chambers track into small chambers does not show expected precision:

shifts in Z-position (precision coordinate) 1-3 mm instead of expected 0.1-0.2 mm

shifts in X- and Y-position 10-13 mm instead of ∼1 mm

shifts in φ angle 30-150 mrad instead of ∼1 mrad

shifts in θ angle 5-9 mrad instead of ∼0.4 mrad

extrapolation to small middle chambers shows best results, extrapolation to small innerchambers is the worst

Possible reasons for under-performance of large chambers track extrapolation:common tracking tools were never tuned for use in muon system

I different magnetic field configuration (toroidal instead of solenoidal)I different extrapolation step size is needed because the MS is much bigger in comparison to IDI considerably inhomogeneous magnetic field in many chambers (this partly explains why extrapolation

into small middle chambers gives better results)

bugs in muon spectrometer part of new common tracking code (in release 12.0.1)I MdtDriftCircle_OnTrack tracking class had bugs in localToGlobal and associatedSurface methodsI there were bugs in RPC digitization code

A lot of things have to be done in order to achieve the desired performance levelSergey Kotov, Jens Schmaler, Oliver Kortner (MPI für Physik, Munich) Alignment of muon chambers with tracks ATLAS-D workshop, Heidelberg, 22.09.2006 11 / 18

First look at segment based alignment of large muon chambers

use track segments associated with the same muon track toestimate the track momentum: ∆α = αout − αin = q

pt

∫Bdl

start with middle chamber segment and extrapolate it to innerand outer chambers using the estimated momentum from ∆α(a simple custom made segment extrapolater is used)

calculate relative translations and rotations of the inner andouter chambers with respect to the middle chamber fromdiscrepancies between extrapolated and measured segments

in the first order approximation, uncertainties in momentumdetermination and segment extrapolation are canceled out withenough track statistics

preliminary study gives the following number of tracks per ηtower needed to achieve 100 µm accuracy of relative chamberalignment:

pµt , GeV Ntracks

6 500k20 20k

for muon calibration stream with rate of 2 kHz and threshold of20 GeV it seems doable


Conclusions and plans

Common tracking tools can be used for fitting tracks in the muon spectrometer

An ATHENA package for track based alignment of small muon chambers has been written butneeds considerable tuning to achieve the required alignment accuracy

Feasibility studies of segment based alignment of muon chambers have been performed andshow promising resultsTo do list:

I run the alignment algorithm with the upcoming release 12.3.0 which has a lot of bug fixes for muonsystem part of common tracking code

I tune the TrkExtrapolater tool for use in the muon spectrometerI continue studies of segment based alignment method for muon chambers


Backup slides


Structure of MuonTrkAlign algorithm

Steps of the MuonTrkAlign algorithm

select an overlap region Track with associated RIOs_OnTrack collection from standard muonreconstruction

divide this collection into four parts: RIOs_OnTrack coming from large chambers andRIOs_OnTrack coming from small inner/middle/outer chambers

refit the “large chambers” RIOs_OnTrack collection with TrackFitter from common trackingtools, using original track as a seed

extrapolate this “large chambers” track into small chambers with TrackExtrapolator and gettrack’s extrapolated parameters

refit inner/middle/outer small chamber RIOs_OnTrack collections with TrackFitter, usingextrapolated “large chambers” track parameters as seed

differences between the refitted inner/middle/outer small chamber tracks and the extrapolated“large chambers” track are the tracking “pseudo” sensors input for ASAP


Check of common tracking tools: position at MS entrance for refitted tracks

x0 [mm]∆-6 -4 -2 0 2 4 60

100

200

300

mµ>=4 ∆<mµ=160 ∆σ


y0 [mm]∆-6 -4 -2 0 2 4 60

100

200

300

mµ>=4 ∆<mµ=165 ∆σ


z0 [mm]∆-1 -0.8 -0.6 -0.4 -0.2 -0 0.2 0.4 0.6 0.8 10

100

200

300

400 mµ>=0 ∆<mµ=24 ∆σ


x0 [mm]∆-6 -4 -2 0 2 4 60

50

100

150

200 mµ>=4 ∆<mµ=191 ∆σ

LrgChmTrk-OrigTrk

y0 [mm]∆-6 -4 -2 0 2 4 60

50

100

150

200mµ>=2 ∆<

mµ=178 ∆σ

LrgChmTrk-OrigTrk

z0 [mm]∆-1 -0.8 -0.6 -0.4 -0.2 -0 0.2 0.4 0.6 0.8 10

100

200

mµ>=1 ∆<mµ=27 ∆σ

LrgChmTrk-OrigTrk


Check of common tracking tools: momentum at MS entrance for refitted tracks

[rad]φ∆-0.005-0.004-0.003-0.002-0.001 0 0.0010.0020.0030.0040.0050

100

200

300radµ>=3 ∆<

radµ=126 ∆σ


[rad]θ∆-0.0015 -0.001 -0.0005 0 0.0005 0.001 0.00150

200

400

radµ>=0 ∆<radµ=39 ∆σ


T/p

Tp∆

-0.2 -0.15 -0.1 -0.05 -0 0.05 0.1 0.15 0.20

200

400

>=-0.0 ∆<=0.4 ∆σ


[rad]φ∆-0.005-0.004-0.003-0.002-0.001 0 0.0010.0020.0030.0040.0050

50

100

150

200 radµ>=1 ∆<radµ=148 ∆σ

LrgChmTrk-OrigTrk

[rad]θ∆-0.0015 -0.001 -0.0005 0 0.0005 0.001 0.00150

100

200

300

400 radµ>=0 ∆<radµ=40 ∆σ

LrgChmTrk-OrigTrk

T/p

Tp∆

-0.2 -0.15 -0.1 -0.05 -0 0.05 0.1 0.15 0.20

200

400

>=-0.0 ∆<=0.4 ∆σ

LrgChmTrk-OrigTrk


Extrapolation of large chambers track into small chambers: positions

X0 [mm]∆-150 -100 -50 0 50 100 1500

20

40

>=-0.3 mm∆<=9.6 mm∆σ

Small inner chamber

X0 [mm]∆-150 -100 -50 0 50 100 1500

20

40

60

80 >=0.3 mm∆<=7.5 mm∆σ


X0 [mm]∆-150 -100 -50 0 50 100 1500

10

20

>=-2.0 mm∆<=15.2 mm∆σ

Small outer chamber

Y0 [mm]∆-150 -100 -50 0 50 100 1500

20

40

>=-0.6 mm∆<=10.3 mm∆σ

Small inner chamber

Y0 [mm]∆-150 -100 -50 0 50 100 1500

20

40

60

80>=-0.5 mm∆<=7.0 mm∆σ


Y0 [mm]∆-150 -100 -50 0 50 100 1500

5

10

15

20 >=-2.0 mm∆<=17.5 mm∆σ

Small outer chamber

Z0 [mm]∆-25 -20 -15 -10 -5 0 5 10 15 20 250

10

20

30

40 >=-0.2 mm∆<=2.4 mm∆σ

Small inner chamber

Z0 [mm]∆-25 -20 -15 -10 -5 0 5 10 15 20 250

20

40

60

80>=0.1 mm∆<=0.9 mm∆σ


Z0 [mm]∆-25 -20 -15 -10 -5 0 5 10 15 20 250

10

20

30

>=-0.1 mm∆<=1.6 mm∆σ

Small outer chamber


Extrapolation of large chambers track into small chambers: angles

[rad]φ∆-1 -0.8 -0.6 -0.4 -0.2 -0 0.2 0.4 0.6 0.8 10

10

20

30 >=-32.8 mrad∆<=200 mrad∆σ

Small inner chamber

[rad]φ∆-1 -0.8 -0.6 -0.4 -0.2 -0 0.2 0.4 0.6 0.8 10

50

100

>=2.0 mrad∆<=33 mrad∆σ


[rad]φ∆-1 -0.8 -0.6 -0.4 -0.2 -0 0.2 0.4 0.6 0.8 10

10

20

>=-0.3 mrad∆<=161 mrad∆σ

Small outer chamber

[rad]θ∆-0.1 -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.10

20

40

60 >=-0.7 mrad∆<=7.5 mrad∆σ

Small inner chamber

[rad]θ∆-0.1 -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.10

50

100 >=-0.1 mrad∆<=4.8 mrad∆σ


[rad]θ∆-0.1 -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.10

10

20

30

40 >=0.6 mrad∆<=7.2 mrad∆σ

Small outer chamber


alignment of muon chambers with tracks file1 overview of the atlas muon spectrometer alignment 2...

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