GEANT4 CMS SI MULATI ON Pedro Arce (CERN/ CI EMAT) (on behalf of CMS collaboration) GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/ CI EMAT) 1
Outline • OSCAR functionality • OSCAR/GEANT4 robustness and performance • Physics comparisons GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/ CI EMAT) 2
OSCAR f unctionality: Geometry • All CMS det ect ors • Also several Test beams • Current ly moving t o geomet ry in XML dat abase, common t o Simulat ion/ Reconst ruct ion/ Visualisat ion • All geomet ry convert ed f rom GEANT3 geomet ry • Building of XML geomet ry int o GEANT4 ready • Already can be visualised wit h I GUANA (heavily used f or debugging) • Missing: det ect or numbering schemes wit h new geomet ry • Will need t o review t he use of ‘Set Smart Less’ (3 year s old) • Det ailed checking quit e advanced • Thorough comparison of GEANT3 and GEANT4 geomet ry • All mat er ials, volumes and t ouchables pr oper t ies • Posit ions of t ouchable cent r es • Mat erial budget • CMS Overlap Det ect ion Tool (now in GEANT4) GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/ CI EMAT) 3
Geometry f or OSCAR XML based Detector Description Language (XML DDL) - Single description inter- face for the ideal detector - Generic description . Materials . Geometry . Component approach - Attaching specific Information to . Components . Subsets of Volumes - Human editable/readable /expandable GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/ CI EMAT) 4
Sliced view of CMS barrel detectors View of CMS muon system View of 180 Higgs event simulated in CMS Tracker detector GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/ CI EMAT) 5
OSCAR f unctionality: Primary generator • CMS part icle gun: • Scan in θ , η , energy • Random (f lat/ gaussian) in θ , η , energy • I nt er f ace wit h HEPEVT ASCI I f iles • I nt er f ace wit h PYTHI A nt uples • Long- lif e particles: • I n GEANT3 only t he decay products are simulat ed • I n GEANT4 t he part icle is simulat ed bef ore decaying (and t he decay product s are kept ) • Advant age: you t ake int o account t he possibilit y of int eract ions, ener gy loss, magnet ic f ield bending, et c. bef ore decaying • The lif e t ime is not kept • The moment um of decay product s is not kept • OSCAR: user can select t o simulat e t he part icles bef ore decaying or simulat e decay products (keeping t he lif e t ime) • Need deeper st udy t o underst and what will be t he f inal solut ion GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/ CI EMAT) 6
OSCAR f unctionality: Persistency • Hits f or all detectors • Primary generator particles • Selected tracks • Use CMS f ramework (COBRA) • Fully compat ible wit h Reconst ruct ion • Using Objectivity , moving t o ROOT (end 2002) GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/ CI EMAT) 7
OSCAR f unctionality: Visualisation � I nteractive visualisation is done wit h I GUANA • Visualise any GEANT4 Geomet r y • Select by logical volumes / by physical volumes • P icking, slices • Volume propert y window • GEANT4 command line • A wizar d t o guide t hr ough OSCAR settings • Adding ot her ext ensions is t r ivial (e.g. GUI s like over lap det ect ion) • Visualise Tracks • Visualise magnet ic f ield • I nt egr at ed wit h over lap det ect ion • Find overlaps, show result det ails in a list • Highlight overlaps in 3D • Hit s, in t he near f ut ure GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/ CI EMAT) 8
OSCAR - I GUANA Overlap detection Example extension (a trivial wizard) Queried from plug-in database, loaded on request and bound to IGUANA G4 Run Manager Control of arbitrary GEANT4 tree Correlated Picking IGUANA viewer displaying OpenInventor scene GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/ CI EMAT) 9
OSCAR - I GUANA: magnetic f ield • 2D plane t hat can be rot at ed • Field direct ion as an arrow • Field int ensit y as colour GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/ CI EMAT) 10
OSCAR f unctionality Physics : • Elect r omagnet ic pr ocesses needed at LHC • Hadronic pr ocesses needed at LHC CMS Physics Technical Design Report is planned to be written using OSCAR (due end 2005) OSCAR milestone Spring/ Summer 2003: “Repr oduce t he physics r esult s of t he GEANT3 simulat ion wit h similar per f or mance” Physics Cuts: • Production cut s per material • Minimum kinetic energy cut s per material • St ill under invest igat ion if we really need t hem • Time of f light cut GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/ CI EMAT) 11
OSCAR f unctionality UserActions: • Several user act ions of the same type loadable on demand Framework: • COBRA manages t he main() and t akes car e of persistency • Now OSCAR is being r eengineer ed t o achieve f ull integration wit h CMS Fr amewor k (see wednesday t alk by M. St avr ianakou) Documentation: • User’s Guide updat ed f or each r elease • doxygen document at ion • Several Tutorials on t he web • For OSCAR developers • For Physics Reconst ruct ion sof t ware developers • For Summer St udent s GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/ CI EMAT) 12
OSCAR f unctionality Future developments: • GEANT4e as GEANE r eplacement (er r or pr opagat ion f or t rack f it t ing) • Under pr ogr ess • GFLASH f or f ast simulat ion • RTAG/ G4 discussion Summary: OSCAR is ready f or physics validation studies GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/ CI EMAT) 13
OSCAR/ GEANT4 robustness Several problems f ound: • Part icles loop bet ween t wo volumes ⇒ push t hem by 0.01 mm • Several G4Except ion f ound: • solved by CMS t eam or/ and wit h t he help of GEANT4 t eam ⇒ >10000 pp events wit hout crashing NOTE: new G4Except ion f ound wit h GEANT4.4.1 (under invest igat ion) GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/ CI EMAT) 14
GEANT4 vs GEANT3 Time Perf ormance - Full event s: H →ττ→µ / t t → e / Z →ττ - Cut s in primary part icles: Pt : 1GeV, | η | < 2.4 (3.0) - Full CMS geomet ry - 3D TOSCA magnet ic f ield - Product ion and t racking cut s as in CMSI M (GEANT3) - GEANT4 voxel navigat ion - GEANT4.4.0.r ef 02 - Pent ium I I I 850 Mhz - Checked t hat t hey are really t he same event s (see next ) GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/ CI EMAT) 15
G3- G4 events detailed comparison H →ττ→µ in all CMS (10 Event s) No Tracks I nitial track energy MeV No Tracks Track length mm GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/ CI EMAT) 16
G3- G4 events: detailed comparison Origin of secondary tracks: R vs Z R (mm) CMSIM (442828 tracks) Z (mm) R (mm) OSCAR (427136 tracks) Z (mm) GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/ CI EMAT) 17
Time perf ormance - H →ττ→µ (10 event s) CMSIM: 439k tracks 64 sec/ evt OSCAR: 400k tracks 117 sec/ evt (1. 83) - t t → e (10 event s) CMSIM: 1809k tracks 184 sec/ evt OSCAR: 1159k tracks 425 sec/ evt (2. 31) - Z →ττ (10 event s) CMSIM: 1105k tracks 96 sec/ evt OSCAR: 941k tracks 248 sec/ evt (2. 58) GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/ CI EMAT) 18
CMSI M(GEANT3) - OSCAR(GEANT4) comparison Central Tracker • Number of rechits per track vs eta Cmsim 122 OSCAR 1 3 2 pre 03 RecHits t muons in region | η | < 100 GeV P 2.5 • resolution vs eta GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/ CI EMAT) 19
CMSI M(GEANT3) - OSCAR(GEANT4) comparison : Muon System reconst ruct ed – generat or quant it ies t muons in region | η | < 5-200 GeV P 2.4 GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/ CI EMAT) 20
I mportance of tuning tracking precision parameters • Big dif f erence bet ween reconst ruct ed and generat ed t rack par amet er s was f ound because t r acking pr ecision par amet er s wer e t oo high. • ‘deltaI ntersectionAccuracy ’ is by def ault 100 µ m • CMS t racker precision 20 µ m • CMS Muon prcision 200 µ m • Has t o be set t o 0.1 µ m • Time j ust increased by 3% GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/ CI EMAT) 21
CMSI M(GEANT3) - OSCAR(GEANT4) comparison : EM calorimeter • SETUP: • CMS elect romagnet ic calorimet er: lead tungstate crystals point ing t o int eract ion point • Photon of E = 30 GeV ent ers f ront f ace of cryst al • No magnet ic f ield • What was compared: • E in hot t est cryst al, in 3x3, in 5x5 mat rix • E t ot al • dN hit s / dt , f or 1 ns t ime slices • GEANT3.21 vs GEANT4.4.0. p02 GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/ CI EMAT) 22
CMSI M(GEANT3) - OSCAR(GEANT4) comparison : EM calorimeter Shower containment: Fr om GEANT4 galler y: Elect ron 5 Gev in PbWO 4 • GEANT3 looks wider t han GEANT4 • Fr om old t est beam GEANT3/ GEANT4 compar ison CMS Note 1997/037 by A.Givernaud: good agreement with G3 for shower profile CMS Note 1998/031 by K.Lassila-Perini: G3 shower is a bit wider than real shower (more detailed) GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/ CI EMAT) 23
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