Robust Alignment of the Inner Detector

Alignment Meeting – 1st June 2005Florian Heinemann

ATLAS

Alignment Challenge Robust Alignment Code

Uncertainties on module positions

Pixel SCTrphi z r rphi z r

Barrel Mounting 10 20 100 100 100

Bowing 100 100

Environment 50

Between Staves / Layers 5 5 100 100 100

Endcap Mounting 25 25 10 10

Bowing 50 50

Environment 20 20 50 50

Between Disks 100 100

Intrinsic Spatial Resolution 15 70 16 600

Richard Hawkings, CERN-PH/ATT, January 2005

µm RMS

Alignment Challenge

5832 modules → 34992 DoF’s

Don’t degrade intrinsic resolution > 20 %

But know position only ~ 100 µm

Get precision with software: At least ~ 10 µm

For W mass ~ 1µm

6 DoF’s

Track based alignment

Robust AlignmentGobal 2

Robust Alignment

ס

ס

A

B

Mean of A – B ≈ 0

Idea: Use overlap residuals for determining

relative module to module misalignment

Overlap residual = outer hit residual – inner hit residual

Robust Alignment

Mean of A – B

≈

Relative misalignment

ס

ס

ס

Idea: Use overlap residuals for determining

relative module to module misalignment

Overlap residual = outer hit residual – inner hit residual

Robust Alignment

Measure Rφ and z overlap residuals for each two overlaps Use residuals also for barrel to barrel alignment Danny Hindson:

Developed software prototype for Pixel and SCT barrel Tested for inter-barrel module shifts in Rφ and z, but no rotations, no

radius change Tested for barrel to barrel alignment Problems with sagitta distortions partly solved with E/p

Advantage: Simple, stable and covers most DoF But: Like FSI and Global 2 might have problem to find simple modes Need:

Migration to Athena Further development like extension to endcap and sagitta removal

Rφ

z

New powerful classes available

System of data handling changed

Code must be invariant to further modifications

Rewrite Code

Software Status Develop in package /InDetAlignment/SiRobustAlign/SiRobustAlign-00-00-0* Input: test.002928.romedig904.higgs120_tautau._000*.pool.root (Rome) Reconstruction presently with xKalman Use Trk::Track tracks from StoreGate Classes used so far:

class IToolSvc;class StoreGateSvc;class Identifier; class EventInfo;class AtlasDetectorID;class AlignSiModule;class AlignSiHit;

namespace Trk { class Track; class TrackStateOnSurface; class INavigator; class IExtrapolator; class IPropagator; class RIO_OnTrack; class TrackParameters;}

namespace InDetDD{ class SCT_DetectorManager; class PixelDetectorManager;}

namespace AIDA { class IHistogram1D;}

namespace SiRobustAlign { class HitOnModule; class RobustAlignAlg : public

Algorithm { public:

Own Algorithm}

Track properties including

hits

Main algorithm and new objects

Gives detector

info

RobustAlignAlg Loop over trackStateOnSurfaces() ->rioOnTrack() Residuals, e.g Rφ = hit->localPosition().x() - trackParVector[Trk::locX] (local frame) Mainly work on the rioOnTrack() level (ESD), but info like cluster size need

prepRawData

First code

in CVS

However, this is

not what I want

In contact with

Edward Moyse

Soon:

Direct way to get

global position

implemented

Overlap residuals 1st test version is running

For single module overlaps: Need higher statistics → Use batch farm

Next steps

Test with misalignment Solve management of histograms Get local misalignment for every module Get uncertainties Perform iterating and refitting Extend to endcaps

Wait for Tool in InDetAlignDBTool

(Richard)

Munich contribution

3D residual – distance of closest approach (DOCA)Calculate local 2 – sum over all tracksCalculate derivatives by moving modulesMinimise 1st order approximation of 2

Go one step in the right directionNo knowledge about achievable precision yet

DOCA

Possible help for

iteration and refitting

Summary - Outlook Migration started Work together with Munich First code is running Aim: Barrel version running and tested in September Still lots to do!