A Virtual Montecarlo (VMC) Application for AMS-01 Alberto Oliva & Nicola Tomassetti, September 2009

Motivation AMS-01 more precise trigger efficiency calculation  comparison between Geant3, Geant4 and Fluka An effordable estimation of the fragmentation systematics  contamination from high charges to low charges Estimation of the VMC framework capabilities in the AMS02 perspective

The Virtual Montecarlo (VMC) Virtual Interface User Code (VMCApp) VMC TGeo GEANT3 VMC TGeant3 GEANT3 Particles Hits GEANT4 VMC TGeant4 GEANT4 FLUKA VMC TFluka FLUKA Output ROOT framework Abstract Layer Physics simulation FORTRAN Tested setup root5.24.00 /+/ geant4.9.2 /+/ fluka2008.3 + dpmjet3 + rqmd_v2.4 /+/ geant321+_vmc.1.11 (GEANT3 + TGeant3) /+/ geant4_vmc.2.7 (TGeant4) /+/ fluka_vmc.0.4 (TFluka) /+/ rqmd_v1.07 + interface (extracted from GBATCH)

Building an application You have to derive the application from the virtual classes: TVirtualMCApplication TVirtualMCStack In these classes there are the some virtual methods needed for the interface with the generic MC: TGeant3 : public TVirtualMC TGeant4 : public TVirtualMC TFluka : public TVirtualMC In the TVirtualMC interface all the MC generic features should be virtualized TVirtualMCApplication InitGeometry() AddParticles() AddIons() BeginEvent() BeginPrimary() PreTrack() // Track (...geant/fluka) Stepping() // Access to the step PostTrack() FinishPrimary() FinishEvent() TVirtualMCStack PushTrack() // Real method PopNextTrack() // Real method PopPrimaryForTracking() // Real method GetNtrack() GetNprimary() GetCurrentTrack() GetCurrentParticle() GetCurrentTrackNumber()

VMC Summary Installation of the AMS01 Geant4 gbatch  Yue Zhou version, used for some production Installation of VMC framework Conversion of the AMS01 G4Geometry to TGeometry  Done automatically (overlaps …)  TEve event display Importing the magnetic field on TVirtualMagField class Output classes  Particles, MCHits Additional ions definitions Primary generator Physics list and cuts (…) From interpreted to compiled  This version is fully independent from GBATCH  No reconstruction, only MC information available

TGeometry AMS01 TEveManager TGeometry is quite similar to G4Geometry: G4Solid (G4Box, G4Tubs, …)  TGeoShape (TGeoBBox, TGeoTubeSeg) G4UnionSolid, G4SubtractionSolid  TGeoCompositeShape G4DisplacedSolid  TGeoShape G4Material  TGeoMedium G4LogicalVolume  TGeoVolume G4PhysicVolume  TGeoVolume + TGeoCombiTrans A simple C++ routine transforms the Yue Zhou G4-AMS01-Geometry in a TGeometry AMS01 TEveManager Magnet

TGeometry: Overlaps Pay attention to region overlaps  FLUKA and GEANT use a different geometric approach (Comb./Hyer.) Overlap between TOF PMTs & TOF support (solved ignoring TOF supports) Other founded overlaps:  Structure overlaps (1 cm, solved)  Markers (solved ignoring makers, better to use TGeoComposite shapes)  TOF Counters and Silicon planes (solved moving PMTs by 4 mm)  TOF Counters and TOF Counters (solved scaling by 2 mm the PMTs)  Ladders overlaps (0.2 mm, solvable but not solved)

Ion Fragmentation Physics Lists GEANT3 GEANT3 Physics + an hadronic pakage (GHEISHA, GFLUKA, GCALOR or MICAP):  works only up to Alpha particles  for heavy ions there are only EM processes In GBATCH there is a RQMD(v1.07) interface able to produce fragmentations:  The code has been adapted to work with TGeant3 in the VMC framework (IGFPAR, several function name, few lines here and there, …) GEANT4 Ion inelastic fragmentations final states are simulated by two models:  Via the G4BinaryLightIonReaction class in the Binary Cascade interaction model (limitations: from 80 MeV to 10 GeV/n, one of the two nuclei must have A < 13)  Wilson Ablation Model (old fashioned geometric approach) For now I’m using the QGSP_BIC_HP Physic List:  wher BIC stands for Binary Ion Cascade  I’ve extended by hand the BIC validity limit!!! FLUKA Uses RQMD(v2.4) between 0.1 and 5 GeV/n Uses DPMJET-3 above 5 GeV/n

Toward a VMC Validation: AMS-01 GSI Beam Test (1998)

AMS-01 GSI Beam Test (1998) Helium runs: 27 M events (186, 446, 896, 2000 GeV/c/n) Carbon runs: 11 M events (330, 446, 896, 2000 GeV/c/n) Cosmic runs: 1.5 M events Sample used Carbon @ » 2 GeV/c/n  » 50 k events Mean 1.847 GeV/n

GSI: Charge Selection Charge ID from STS-91 data Nicola’s Toy MC (constructed with STS-91 data) Application of Nicola’s Charge ID (constructed with STS-91 data) Zreconstructed Zgenerated Deconvolution Charge ID from STS-91 data Toy MC for contamination estimation GSI charge distribution Exact unfolding (decontamination)  GSI fragmentation estimation

GSI: VMC Simulation C12 @ 2 GeV/n/c p @ 2 GeV/c

GSI: Inelastic interaction probability G3-VMC G4-VMC Low e shield Upper TOF Lower TOF Tk1 Tk2 Tk3 Tk4 Tk5 Tk6 FL-VMC The trigger is simulated according to a very simple digitization scheme.

GSI: MC/Data Comparison G3-VMC 3.1% 1.1% 0.7% G4-VMC FL-VMC 4.9% 2.8% 1.5% 0.8% 0.8% 0.4%