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Detector Description in LHCb

Detector Description in LHCb. Introductions to Gauss and GEANT4 in previous lectures Goal: To simulate the performance of the real detector Simulation involves, among other things, creating the geometry and material descriptions in the database. Detector Simulation.

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Detector Description in LHCb

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  1. Detector Description in LHCb

  2. Introductions to Gauss and GEANT4 in previous lectures Goal: To simulate the performance of the real detector Simulation involves, among other things, creating the geometry and material descriptions in the database. Detector Simulation

  3. General Overview of detector Description Concept of Volumes and Detector Elements Geometry visualization Considerations for Design Outline

  4. Converter Converter Application Manager Converter Event Selector Transient Event Store Data Files Message Service Persistency Service Event Data Service JobOptions Service Algorithm Algorithm Algorithm Data Files Transient Detector Store Particle Prop. Service Persistency Service Detec. Data Service Other Services Data Files Transient Histogram Store Persistency Service Histogram Service Detector Description Architecture • Sub-Architecture of Gaudi • Same principles • Transient/Persistent representations • Focus on the “Physics Algorithm” • Access to Detector Transient Store • Coherent access to “all” detector data • Geometry, Calibration, Slow Control, etc. Gaudi Architecture

  5. Detector Description • Logical Structure : Gaudi (LHCb) • Breakdown of detectors • Identification • Geometry Structure : Gaudi(LHCb) copied to GEANT4 • Hierarchy of geometrical volumes • LogicalVolumes (unplaced dimensioned shape) • PhysicalVolumes (placed volume) • Other detector data : Gaudi (LHCb) • Calibration, Alignment, Readout maps, Slow control, etc.

  6. HCALModule Experiment HCAL RICH ECAL Tracking Module2 Module1 HCAL LHCb LHCb ECAL Calo DetElement PVolume LVolume DetElement LVolume DetElement DetElement DetElement DetElement LVolume DetElement DetElement PVolume LVolume PVolume LVolume PVolume PVolume Two Hierarchies Logical structure Geometry structure Detector Description Geometry

  7. Volumes • Logical Volume: Contains the info of the Shape and Material of a Volume • Physical Volume : Contains the placement info of the Logical Volume • ie. Physical location and orientation of a Volume. • Logical Volume also has • (a ) the information regarding • which other physical volumes are contained in that Volume. • (b ) the graphics attributes needed for visualization. • ( c ) user defined parameters • needed for tracking, electromagnetic field. • ( d ) flags to indicate if the volume is a sensitive detector • ( to create hits) • The syntax for creating these objects in the DB : Definition in DTD files. • One can use the current DB • as an example. More info: LHCb-2004-020

  8. Shapes: Attributes to Volumes Shapes: CSG (Constructed Solid Geometry) Solids, BREPS (Boundary Represented Solids) , Tessellated Solids Shapes in LHCb ( CSG ) : Box, Tubs, Cons, Trd, Sphere etc. Simple shapes,. Easy to use and gives better performance compared to other Types. Geant4 has even more CSG shapes. We use the ones available in LHCb. Boolean operations: Combination of two solids. (Subtraction, intersection ,union etc). For performance reasons unions are avoided in general. Also Boolean operations with disjoint solids or those that share the surfaces to be avoided. More info: LHCb-2004-018 Geant4 also has: BREPS: Volumes defined by the description of their boundaries Tessellated Solids: Volumes defined by a number of facets. Useful for importing complex shapes created by CAD systems. More Info: http://geant4.web.cern.ch/geant4/UserDocumentation/UsersGuides/ForApplicationDeveloper/html/ch04.html This tutorial: CSG solids , Boolean operations . Use shapes available in LHCb.

  9. Logical Structure • The basic object is a Detector Element • Identification • Navigation (tree-like) • DetectorElementis an information center • Be able to answer any detector related question • E.g. global position of strip#, temperature of detector, absolute channel gain, etc. • Placeholder for specific code • The specific answers can be coded by “Physicists” • DetectorElement objects are shared by all Algorithms DetElement * MyDetector

  10. MuonStation DetElement ReadOut Algorithm Accessing Detector Data • Manages store • Synchronization updates beginEvent DetectorData Service Persistency Service request request: get, update Transient Detector Store Geometry Conversion Service IDetElement IGeometryInfo GeometryInfo Algorithm ICalibration Conditions DB Calibration Conversion Service IReadOut reference Other DBs Conversion Service • More about detector elements in the following lecture

  11. Transient Store Organization • Standard Gaudi Transient Store • “Catalogs” of Logical Volumes and Materials • “Structure” as a tree • All elements identified with names of the form: /xxx/yyy/zzzz

  12. Persistency based on XML files • XML is used as persistent representation of the Structure, Geometry and Materials • Why XML? • Instead of inventing our own format use a standard one (extendible) • Many available Parsers and Tools • Considered as Strategic technology a decade ago. • Divided into 3 main parts • structure • geometry • material • All these defined by the DTD files

  13. The data is accessed from an SQLITE or ORACLE database when running the applications. Data created is converted into these formats during DB updates. The DB creation is normally done by creating text files which are in XML format. One can also run from a ‘DB slice’ which is in XML format. The tags to use in these XML files are defined in the ‘DTD’ files. One needs to create the DB using the syntax specified by the DTD files. In this tutorial, few examples of this , would be discussed. Persistency: Data base technologies

  14. Some Examples of XML • Expressions evaluator – units & functions known • 12.2*mm + .17*m / tan (34*degree) • parameter : a kind of macro <parameter name="InCell" value="40.6667*mm"/> <parameter name="MidCell" value="1.5*InCell"/> • References : element + “ref” <detelemref href="LHCb/structure.xml#LHCb"/>

  15. Example of a Volume : Small Simple Box (SSB) <parameter name="TexSSBXSize" value= "70*mm" /> <parameter name="TexSSBYSize" value= "120*mm" /> <parameter name="TexSSBZSize" value= "90*mm" /> <logvol name="lvTexSSBBasic“ material="IT/G10"> <box name="TutorialExampleSSBBasicBox" sizeX="TexSSBXSize" sizeY="TexSSBYSize" sizeZ="TexSSBZSize" /> </logvol> • This Logical Volume has also the • Visualization attribute (color)

  16. Example of a Boolean Solid: SSB with a hole <logvol name="lvTexSSBTypeA" material="IT/G10"> <subtraction name="TutorialSSBTypeASub" > <box name="TutorialExampleSSBTypeAWithSubBox" sizeX="TexSSBXSize" sizeY="TexSSBYSize" sizeZ="TexSSBZSize" /> <tubs name="TutorialSSBTypeAHoleCyl" sizeZ="TexSSBZHoleLargeZSize" outerRadius="TexSSBZHoleRadius" /> <posXYZ x="TexSSBZHoleAXLocation" y="TexSSBZHoleAYLocation" /> </subtraction> </logvol>

  17. Geometry Elements :Examples • DDDB : the root • catalog : a list • logvol : logical volume • physvol : physical volume • paramphysvol(2D)(3D) : replication of physical volumes • tabproperty : tabulated properties <DDDB> <catalog name=“…”> <logvol material=“…” name=“…”> <physvol logvol=“…” name=“…”/> </logvol> <logvol name=“…”> <paramphysvol number="5"> <physvol logvol=“…” name=“…”/> <posXYZ z="20*cm"/> </paramphysvol> </logvol> </catalog> </DDDB>

  18. Geometry Elements(2) • posXYZ, posRPhiZ, posRThPhi : translations • rotXYZ, rotAxis : rotations • transformation : composition of transformations • box, trd, trap, cons, tub, sphere • union, intersection, subtraction : boolean solids • surface <subtraction name="sub2"> <box name="box3“ sizeX="1*m“ sizeY="1*m“ sizeZ="15*cm"/> <tubs name="tub2“ outerRadius="15*cm“ sizeZ="25*cm"/> </subtraction> <posXYZ z="-40*cm"/> <rotXYZ rotX=“90*degree”/>

  19. Material Elements: Examples <isotope A="11*g/mole“ name="Bor_11“ …/> <element name="Boron“ symbol="B“ …> <isotoperef href="#Bor_10“ fractionmass="0.20"/> <isotoperef href="#Bor_11“ fractionmass="0.80"/> </element> <element name="Oxygen“ symbol="O“ …> <atom A="16*g/mole“ Zeff="8.0000"/> </element> <material name="CO2“ …> <component name="Carbon“ natoms="1"/> <component name="Oxygen“ natoms="2"/> </material> • materials : the root • catalog : a list • tabproperty: tabulated properties • atom • isotope • element : a mixture of isotopes • material : mixtures of elements or materials

  20. Structure Elements:Examples <DDDB> <catalog name=“…"> <detelem name=“…"> <geometryinfo lvname=“…” npath=“…” support=“…”/> <userParameter comment=“…” name=“…” type="string"> … </userParameter> <specific> … </specific> </detelem> </catalog> </DDDB> • DDDB : the root • catalog : a list • detelem : a detector element • geometryInfo : connection to the geometry • userParameter(Vector) : hook for adding parameters • specific : hook for extending the DTD

  21. Designing the Detector Description • First find what all parts need to be simulated. • Discuss the design with colleagues. • When designing: Everything should be made as simple as possible, but not simpler. A. Einstein • Check with graphics to see what you created is OK. • Test for overlaps • Run particles through to see if it gives the hits as intended • Test with full b-event simulation • Create the detector elements as needed. • Write events out and then run through the reconstruction for verification.

  22. The concept of Volumes and detector elements are introduced • Practical examples and exercises in the next part. Summary

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