G4 Geometry status & plans John Apostolakis for Geometry and Transportation Working Group

20th September 1999 J. Apostolakis, CERN 2 What I will talk about n Briefest overview of Geometry n Developments over the last year since beta01 / Niigatasince beta01 / Niigata n Changes since production release improvements, fixesimprovements, fixes n Plans for future n Some detectors

20th September 1999 J. Apostolakis, CERN 3 What the geometry does... Describes a Detector n Hierarchy of volumes n Many volumes repeat Volume & sub-treeVolume & sub-tree n Up to millions of volumes for LHC era n Import detectors from CAD systems Navigates in Detector n Locates a point n Computes a step Linear intersection Field propagation: n Integration of motion n Chord intersection

20th September 1999 J. Apostolakis, CERN 4 Major developments in last year n Boolean solids new solids from Union, Intersection, Subtr.new solids from Union, Intersection, Subtr. n New specific solids (CSG-like implementations) new Hype solidnew Hype solid Pcone and polyhedra:new implementationsPcone and polyhedra:new implementations n BREPs and STEP: see later talk (G.Cosmo) n Field tracking of spintracking of spin ability to track in Electric fieldability to track in Electric field

20th September 1999 J. Apostolakis, CERN 5 Creating a Detector Volume n Start with its Shape & Size Box 3x5x7 cm, sphere R=8mBox 3x5x7 cm, sphere R=8m n Add properties: material, B/E field,material, B/E field, make it sensitivemake it sensitive n Place it in another volume in one placein one place repeatedly using a functionrepeatedly using a function Solid Logical-Volume Physical-Volume

20th September 1999 J. Apostolakis, CERN 6 Boolean Solids: what are they n STEP compliant Boolean operations n A Boolean solid is built from two solidstwo solids an operationan operation an optional tranformation for one solidan optional tranformation for one solid n Solids that can be used: CSG solidsCSG solids other Boolean solidsother Boolean solids

20th September 1999 J. Apostolakis, CERN 7 Boolean Solids (status) n Boolean solids can be used exactly like any other solidsexactly like any other solids n Implementation: V. Grichine Design: J. Apostolakis, S.Giani.Design: J. Apostolakis, S.Giani. n First implementation complete n Further testing improvements in progressimprovements in progress

20th September 1999 J. Apostolakis, CERN 8 New Specific Solids n New Hype solid Created, eg, by rotation hyperbola / axisCreated, eg, by rotation hyperbola / axis –E. Lamana’s group (Rome / IGD) n Polycone and polyhedra alternative implementation (to BREP)alternative implementation (to BREP) –D. Williams (BaBar) angle-limitted Pconeangle-limitted Pcone –S. Magni (Milano/IGD)

20th September 1999 J. Apostolakis, CERN 9 Magnetic Field n Integrates motion in a field n Finds intersection with volume boundary n Framework could support any type of field but in beta-01but in beta-01 –only magnetic field worked –only position/momentum direction tracked

20th September 1999 J. Apostolakis, CERN 10 Field developments (Niigata to now) n Modifications to state adding Energy, Spin, Time of flightadding Energy, Spin, Time of flight –J. Apostolakis n New forces spin precessing in magnetic fieldspin precessing in magnetic field –P. Gumplinger (in release 4.0.1) in electric field (including E & B)in electric field (including E & B) –V. Grichine

20th September 1999 J. Apostolakis, CERN 11 Accuracy in field Accuracy in field n 5mm thick cone Aluminium in AirAluminium in Air n Geant3 misses for 10 degrees max deviation (default=20)for 10 degrees max deviation (default=20) in 50% of trial tracksin 50% of trial tracks need small angle <2 degneed small angle <2 deg n Geant4 always hits

20th September 1999 J. Apostolakis, CERN 12 Geometry Improvements n Optimisation of Voxelisation –Request: BaBar, CMS, Borexino small code changesmall code change much faster initialisationmuch faster initialisation no runtime penaltyno runtime penalty –S. Giani n Visualise voxels –L. Graignac … curved tracks unfinished

20th September 1999 J. Apostolakis, CERN 13 Fixes have been made to correct n Replica volume navigation problem leading to loop eliminatedproblem leading to loop eliminated n Race condition in field at boundary –Reported by BaBar, Ecole Polyt. in strong field and detailed geometryin strong field and detailed geometry

20th September 1999 J. Apostolakis, CERN 14 Plans/Extensions n A new concept: a “frame” it is a collection of logical volumeit is a collection of logical volume each one positioned in frame’s coordinateseach one positioned in frame’s coordinates that can be placedthat can be placed –as a unit in a “mother” logical volume –this can be done repeatedly it is a factory/only aids in creating geometryit is a factory/only aids in creating geometry –the Navigator does not see ‘frames’ request: Atlas (M.Asai,..)request: Atlas (M.Asai,..)

20th September 1999 J. Apostolakis, CERN 15 Plans (cont.) n Improve field perfomance work on benchmarkingwork on benchmarking modify code to use safety informationmodify code to use safety information n Converting Geant3 ‘many’ geometries find out whether/where there are use casesfind out whether/where there are use cases –contact us document how Geant4 handles thesedocument how Geant4 handles these possibly provide a tools for simple casespossibly provide a tools for simple cases

20th September 1999 J. Apostolakis, CERN 16 Physical Volumes n Placement: it is one positioned volume n Repeated: a volume placed many times can represent any number of volumescan represent any number of volumes reduces use of memory.reduces use of memory. Replica: simple repetition, like G3 divisionsReplica: simple repetition, like G3 divisions Parameterised: function (NEW)Parameterised: function (NEW) n A mother volume either n A mother volume can contain either many placement volumes ORmany placement volumes OR one repeated volumeone repeated volume repeated placement

19th May 1999 J. Apostolakis, CERN 17 Plans (cont.) n Parameterising the daughters of a Parameterised Physical volume extends flexibilityextends flexibility allows volumes of different size/solidallows volumes of different size/solid –to have their own daughters because up to now they could only be ‘leaf’ nodesbecause up to now they could only be ‘leaf’ nodes it is currently under study/discussionit is currently under study/discussion

20th September 1999 J. Apostolakis, CERN 18 Navigation Navigation n Responsible for Locating a point’s VolumeLocating a point’s Volume Step ComputationStep Computation –computes safety with step –must relocate before each computeStep can be ‘expensive’can be ‘expensive’ n New capabilities: Safety ComputationSafety Computation Relocate Within VolumeRelocate Within Volume

20th September 1999 J. Apostolakis, CERN 19 Changes in the past year n Boolean solids new solids from Union, Intersection, Subtr.new solids from Union, Intersection, Subtr. n New specific solids (CSG-like implementations) new Hype solidnew Hype solid Pcone and polyhedra:new implementationsPcone and polyhedra:new implementations n Field tracking of spintracking of spin ability to track in Electric fieldability to track in Electric field n Fixes in solids, navigator, field.

AIHENP 99, Crete, April 99 V. Lefebure CMS/CERN 20 CMS Geometry in G EANT 4 current status n Beam Pipe n Tracker Si Pixel DetectorsSi Pixel Detectors –Barrel Si Pixel –Forward Si Pixel Si Strip DetectorsSi Strip Detectors –Barrel Si Strip MSGCMSGC –Barrel MSGC n Calorimeters Electromagnetic CalorimeterElectromagnetic Calorimeter –Barrel ECAL Hadron CalorimeterHadron Calorimeter –Barrel HCAL n Muon System Barrel MuonBarrel Muon

AIHENP 99, Crete, April 99 V. Lefebure CMS/CERN 21 Barrel Si Pixel Barrel Si Pixel G EANT max. radius = 11 cm length = 60 cm Magnetic Field Magnetic Field

20th September 1999 J. Apostolakis, CERN 22 Simulation in Borexino n Old code: ray tracer simplified trackingsimplified tracking no reflections, phys.no reflections, phys. n Geant4 code reproduces resultsreproduces results photons tracked everywherephotons tracked everywhere flexible, extensibleflexible, extensible immediate benefit: new under-standingimmediate benefit: new under-standing

20th September 1999 J. Apostolakis, CERN 23 Benefits of Geant4 (Borexino) n Full geometry n All optical processes reflection, refractionreflection, refraction n New process for specialised physics of scintilatorfor specialised physics of scintilator –scatter, absorption, re-emission S. Magni, G. PieriS. Magni, G. Pieri

20th September 1999 J. Apostolakis, CERN 24 Atlas Geometry

20th September 1999 J. Apostolakis, CERN 25 BaBar’s Simulation: “Bogus” n Fast Simulation commisioned April 99 n Simple geometry n Parameterisation processes hits on detector elements create reconstruction objectshits on detector elements create reconstruction objects

20th September 1999 J. Apostolakis, CERN 26 BaBar full simulation n SVT N. Kuznetsova,UCSBN. Kuznetsova,UCSB n Under development n First full version of Geometry soon, e.g. EMC from g3tog4EMC from g3tog4 –J. Allison

20th September 1999 J. Apostolakis, CERN 27 Geometry: Recent developments n Boolean operations, a-la STEP: a solid is created by usinga solid is created by using –an operation (union, intersection, subtraction) –between two solids for CAD export, only use with CSG solidsfor CAD export, only use with CSG solids n Tracking of spin in magnetic field n New solids (hype, alternative pcon/pgon)