ACAT05 - DESY Zeuthen125/05/2005 Detector Description of the ATLAS Muon Spectrometer and H8 Muon Testbeam D. Pomarède CEA/DAPNIA/SEDI/LILAS - Saclay

25/05/2005ACAT05 - DESY Zeuthen 1

Detector Descriptionof the

ATLAS Muon Spectrometerand H8 Muon Testbeam

D. PomarèdeCEA/DAPNIA/SEDI/LILAS - Saclay

ACAT05 25/05/2005 2D. Pomarède, CEA/DAPNIA/LILAS

•The ATLAS Muon Spectrometer

•Challenges of the Muon Detector Description

•Integration in the ATLAS software chain

•Implementation in the ATLAS Simulations and Data Challenges

•Implementation in the H8 Muon Testbeams

•Conclusions & Plans

Outline


The ATLAS Muon Spectrometer

•High-momentum final-state muons are among the most promising and robust signatures of physics at the Large Hadron Collider (LHC)

•To exploit this potential, the ATLAS Collaboration has designed a high-resolution muon spectrometer with stand-alone triggering and momentum measurement capability

•The final aim is to reach the highest efficiency with stand-alone mo-mentum resolution of a few % at 10-100 GeV/c and ~10% at 1 TeV/c

•The spectrometer is based on the magnetic deflection of tracks in large superconducting air-core toroid magnets. The tracks are measured in chambers laid out in three layers. An optical alignment system controls the relative positioning of chambers at the 30 m level.

•The layout of the detectors and their intrinsic design are optimized to provide the best acceptance and resolution, taking into account the high-level background environment, the inhomogeneous magnetic field, and the large size of the apparatus.


The ATLAS Muon Spectrometer

Barrel Toroid Magnet

24

met

er

dia

me

ter

44 meter length

EndCap Toroid Magnet

Muon Chambers


Challenges of the Muon Detector Description

•Four technologies of detectors are used :– Precision chambers : MDT (Monitored Drift Tubes Chamber) and CSC

(Cathode Strips Chamber)– Trigger chambers : RPC (Resistive Plate Chamber) and TGC (Thin Gap

Chamber)

•A large number of chambers with different properties : – E.g. ~1200 MDT chambers– Rectangular or trapezoidal shapes with various sizes– 1 or 2 Multilayer per chamber– 3 or 4 layers of tubes per Multilayer– 30 to 72 tubes per layer– Some chambers have cutouts

Example : EndCap Outer Large MDT chamber dim 1.4 x 6.2 meters2 Multilayers with 3 layers48 tubes / layer



•A complex layout•Organization in Large and Small

sectors associated with the eight Magnet coils

•Cylindrical symmetry broken by the feet : special sectors

•Mirror symmetry z+/z- broken by holes for access and services (cables, cryo- genics)

Layout of the Barrel MDT chambers with the Barrel Toroid and Feets


Precision Measurements in 3 locations in the bending plane

Trigger and 2nd coordinate Measurements


• Complex layout of chambers in the bending plane

Z-axis (LHC beam)

Interactionpoint

B



•Alignment of chambers– 6 parameters per chamber to describe the translations and rotations w.r.t

nominal positions

•Deformations of chambers : 8 parameters (Torsion, Cross Plate Sag (RO/HV), Cross Plates elongations (RO/HV), Long- beam sags, Trapezoid effect) + global Temperature expansion

EndCap Middle Large MDT chamber with a 150 mm Torsion

Barrel Outer Large MDT chamber with a combination of Torsion (100 mm) and

Cross Plate sags (50 mm)



•A precise description of the passive materials is needed to account for the multiple Coulomb scattering and energy losses : Magnets, Supports, Shields

Barrel and EndCap Toroids, Shields and Support Structures


Implementation and integration in the ATLAS SW Chain

•The detector description relies on two key components : the Database that holds the geometrical parameters and the software that access it and builds the geometry

•The entire chain of simulation, reconstruction, calibration packages depend upon the Detector Description

– A stable and robust implementation is required– It must be flexible enough to answer the need of schema evolution and allow for

possible layout changes : one version of the software should handle many different possible geometrical configurations held in the Detector Description Database

– Database distribution (GRID-based operation)

•The AMDB ascii file is the primary source for geometry parameters– “Atlas Muon DataBase” specific to the Muon system– Structured organization of active elements (detectors)

• reproduce the natural symmetries of the detector • compact, object-oriented• indexing of objects similar to the offline identifier scheme

– XML description of passive elements (AGDD)– Visualization tool to develop and debug the geometry : Persint

•The Oracle Detector Description Database is a unified source of the AMDB parameters for the detector description packages

– Common to all ATLAS subsystems (Calorimeters, Inner Detectors)– Supported by CERN-IT, MySQL-replicas available– Versioning supported to allow for multiple versions of the geometry, Browser


AMDB DESCRIPTION OF ACTIVE ELEMENTS

•Example of Barrel Inner Large (BIL) chambers layout


AMDB/XML DESCRIPTION OF DEAD MATTER

•Example of Disk Shield Small Wheel Hub :

Primary variables

volume polycone with two child-

elements (polyplanes)

Composition of volumes : Disk Shield


Oracle DDDB Browser

AMDBtables

Tags of ALMN tables(definition of objects

in Muon stations)


Tag Hierarchy Browser

List of tags of ATLASgeometry

List of tags of Muongeometry

List of tagsof AMDB

Tags ofAMDBtables



•The software packages retrieve the parameters from the DB and provide the geometrical informations to the clients in the software framework :

– the Amdcsimrec package provides a set of methods to obtain all geome-trical informations to build the internal geometry of the client applications

• tightly coupled to the AMDB database

• schema evolution : a number of different geometries can be described with a single implementation of the software

• complex volumes are described using boolean volume operations

• visualization tool : Persint

– the MuonGeoModel package introduced in 2003 • uses a geometry kernel common with all other ATLAS subsystems :

– the GeoModel kernel provides a set of geometrical primitives of common use (tube, box, polyhedron, …)

– detector-specific services that are not described in a generic way are implemented as an additional layer

– it provides volume operations

– it has CLHEP as sole dependency

– visualization tool : HEPVis

• used by Geant4 simulations


A picture of the whole system Barrel & CSC Stations

EndCap Stations & Innert Materials

Implementation and integration in the ATLAS SW Chain• Implementation with the MuonGeoModel package :


MDT & RPC internal structure EC tubes staircasing

BMS MDT+RPC stations CSC internal structure



Implementations in the Simulations and Data Challemges

•The design of the Spectrometer was optimized using this Detector Description :

– ATLAS Muon Spectrometer Technical Design Report, 1997

•Evaluation of the ATLAS Physics performance (“Layout M”)– Geant3 simulations

– Detector and Physics Performance Technical Design Report, 1999

•Studies of realistic service and access holes, 2001•ATLAS Data Challenge 1 (“Layout P”), 2001-2002

– Geant3 simulations

– Athens Physics Workshop 2003

•ATLAS Data Challenge 2 (“Layout Q”), Ongoing– Geant4 simulations

– GRID based

– Rome Physics Workshop, June 6-11 2005


•Example of Higgs to four muons event. Detector Description AMDB, Track reconstruction Muonboy, Display Persint

Simulations


H8 MUON TESTBEAM

•Major testbeams have been conducted at the CERN-SPS H8 line since 2001 to test the Muon detectors

•One of the main objective was to validate the concept of the optical alignment systems of the Muon chambers.

•Detector Description is a key component of these tests :– Description of the nominal geometry– Misalignment of chambers w.r.t nominal positions– Deformations of chambers– Implementation of the geometrical models in both the alignment

reconstruction programs (analysis/fitting of data from optical devices) and track reconstruction

– Also, test of the description of dead materials : comparison MC/data

•Analyses have demonstrated that the geometry can be controlled using alignment corrections from the optical alignment systems

– various movements (translations, rotations) and deformations tested– Barrel and EndCap systems– chambers aligned at the 30 micron level


Combined Testbeam Geometry

Magnets

Barrel setup (2 towers MDT+RPC)

EndCap MDT setupCSC

TGCs

BOS MDT+RPC station

Iron Dump

BIS chamber

H8-2004 Combined Testbeam final configuration : 15 MDTs, 7 RPCs, 3 TGCs, 1 CSC

RotatingBIL


H8 MUON TESTBEAM TYPICAL ENDCAP EVENT


H8 MUON TESTBEAM TYPICAL ENDCAP EVENT


Conclusions and plans

•A well established Detector Description used in the optimization of the detector and throughout the evaluations of the Physics perfor-mance of ATLAS : large-scale simulations and testbeams

•Plans :– Commissioning of Muon Spectrometer with cosmics

• Barrel Sector 13 : 6 BML and 6 BOL stations, summer 2005

– Data Challenge 3 / Computing System Commissioning• with the most up-to-date geometry (“Layout R”)• misaligned / deformed chambers

– Refinements of the chambers description• chamber intrinsic properties from X-ray tomography or analyses of

cosmic-ray test stands : tube pitches, non-parallelism of multilayers

– Refinements of dead matter description• electronics, cables, patch panels• additional dead matter : access platforms


Description of Access Platforms

•Example of current developments : description of the access platforms clamped on the Barrel Toroid struts = additional contribution to Multiple Coulomb scatterring


Description of Access Platforms

Documents

ACAT05 - DESY Zeuthen125/05/2005 Detector Description of the ATLAS Muon Spectrometer and H8 Muon Testbeam D. Pomarède CEA/DAPNIA/SEDI/LILAS - Saclay