20 June 2015Christian Hansen, CERN1 A Software Service Routine describing the Atlas Inner Detector Materials Steve Armstrong, Christian Hansen and Rikard Sandström November 2002, Uppsala This talk can be found at

20 June 2015Christian Hansen, CERN2 Introduction - LHC The Large Hadron Collider (LHC) at CERN ATLAS, A Toroidal LHC ApparatuS

20 June 2015Christian Hansen, CERN3 Introduction – Inner Tracker Measures the directions, momenta, and charge of particles produced in each proton-proton collision Consists of three different systems Pixel Detectors Silicon Strip Detectors, SCT Transition Radiation Tracker, TRT All in a solenoidal magnetic field parallel to the beam axis

20 June 2015Christian Hansen, CERN4 Introduction – Reconstruction 10 azimuthal positions from Pixel and Strip detectors (r < 50 cm) 36 azimuthal positions from TRT (50 cm < r < 100 cm) These signals are sorted into patterns produced by helical trajectories Then directions, momenta and charge for the particles are determined It is needed to select 1 interesting event out of 10 million background events The particle tracks can be distorted by the material of the detector For more accurate reconstruction the information about the material in the detector will be provided to the reconstruction packages by the Material Integration Service (MIS)

20 June 2015Christian Hansen, CERN5 Introduction - MIS Material Information for ID is presently hard coded differently in various Reconstruction Packages Our goal is to provide a service reading from GEANT ID descriptions

20 June 2015Christian Hansen, CERN6 Use of GEANT User defined number of Geantinos sent out spherically (TRTSimG4, Zalite) Example of a parameter set Geantinos take new StepPoint for each new material element encountered For each StepPoint, RadiationLength is given from GEANT4 26. Production of a GeantinoMap: #179 #180 #181 #182 #183 #184 #185

20 June 2015Christian Hansen, CERN7 VolumeElement Vs. GeantinoStep Approach ID is segmented into cylindrical VolumeElements (VE) Each VE has an average RadiationLength ( X 0 ) User specified line between x 1 and x 2 intersects VEs and the x/X 0 is determined Suitable for fine spaced structures In TRT used for wires, gas, straws, radiator and twistor VolumeElement (VE) Approach: Geantinos take a new step for each new material Each GS are saved with its RadiationLength ( X 0 ) The line between x 1 and x 2 has GS projected on to it and x/X 0 is determined Suitable for disjoint structures in TRT used for support, module, SCTService and cooling GeantinoStep (GS) Approach:

20 June 2015Christian Hansen, CERN8 MIS – VolumeElement Approach Each VE gets its average RadiationLength (X 0j ) from intersecting geantinos Each VE gets the length that the line between x 1 and x 2 is intersecting it (  x j ) The  x j / X 0j, for each intersected VE are summed together

20 June 2015Christian Hansen, CERN9 MIS – The Geantino Step Approach For large structures (like support) the GeantinoSteps and X 0 are saved GeantinoSteps are projected on to line between x 1 and x 2 RadiationLengthFraction between x 1 and x 2 is sum of ProjectionSteps  (x i / X 0i ) Works in 3D!!!

20 June 2015Christian Hansen, CERN10 RadiationLengthFraction (x/X 0 ) for TRT Disagreement since the methods are under development Step Approach PRELIMINARY!!! VolumeElement Approach An attempt to reproduce G4 values by the use of Step Approach and VolumeElement Approach

20 June 2015Christian Hansen, CERN11 Future Plans Continue to validate results (converting to G4) Benchmark speed / optimize performance MIS Continuing to encounter substantial challenges using ATLSIM (Hope to continue work with Fred Luehring (TRT) and Pavel Nevski) Draft to ATLAS note is being prepared and available : /afs/cern.ch/user/c/chansen/PUBLIC/MATERIALINTEGRATIONSERVICE/DOCUMENT/mis.tex G4G3MuonRelease Pixels: Working with Davide Costanzo’s G4Pixel SCT: Plan to work with Andrea Dell’Acqua’s G4Sct Have had nice discussions with Ada Farilla and Armin Nairz Have given status tutorial of MIS to Armin Difficult to assign dates – work preliminary May not be possible to include in Release Everything in /afs/cern.ch/c/chansen/PUBLIC/