LSO Cal Geant4 Simulation S. Germani INFN Perugia SuperB R&D Workshop SLAC 15/02/08

Pourpose and Outline Pourpose: Geant 4 simulation to prepare beamtest LSO crystals prototype for Fwd ECAL (2009) Outline: Intro Leakage Deposited Energy Deposited Energy Fit Dead Material and Modularity Effect BaBar and CMS ECAL examples Adding Projectivity Dead Material variation Upstream Matreial Effect Slab Dummy SVT and DCH Difference between e- and  beam Conclusions and Outlook SLAC 15/02/08 LSO Cal G4 Simulation

Intro Study: First approch Geometry is a NxN LSO crystals matrix: Crystals dimentions: 2x2x20 cm (17.54 X0) No Dead Material Particles Beam: e- Energy: 50 (100 MeV)  5 (9)GeV Direction: horizontal Position: at the center of the matrix Study: Deposited energy Leakage SLAC 15/02/08 LSO Cal G4 Simulation

Deposited Energy and Leakage Matrix 9x9 Fwd leak Laterlal leak Backsplash Matrix 21x21 No Lateral Leak SLAC 15/02/08 LSO Cal G4 Simulation

Edep Fit Tested Asymmetrical Gauss function to fit the distribution of the Fraction of Deposited Energy (Edep/Ebeam): P1 : most probable value (mpv) P2*(P3-x) : running  0.5 GeV 2.0 GeV 9.0 GeV SLAC 15/02/08 LSO Cal G4 Simulation

Mean vs mvp and RMS vs  As expected Mean and peak position (mpv) have different values but similar scaling with the energy Chose running  value at E=Epeak as performance reference Deposited energy RMS and (E=mpv) have different values but similar scaling with the energy From now on use (mostly) mpv and (E=mpv) for performance evaluation SLAC 15/02/08 LSO Cal G4 Simulation

Adding Dead Material and Modularity BaBar like geometry (B.Aubert et al. Nucl.Instrum.Meth.A479:1-116,2002) : Each Crystal wrapped with 2 x 165 µm Tyvek 25 µm Al 13 µm Mylar Each module wrapped with 300 µm Carbon-fiber CMS like geometry (CMS EDR IV ) : Crystal inside Carbon Fiber matrix Inner wall thickness 400 µm Outer wall thickness 200 µm Crystal Carbon Fiber clearance 100 µm Module Gap 100 µm Mylar C Fiber Al Tyvek Crystal Crystal Air 3x3 Module 3x3 Module Carbon Fiber Air SLAC 15/02/08 LSO Cal G4 Simulation

Dead Material and Modularity effects BaBar like Dead material across modules not negligible Module Size (3x3, 5x5) affect performances CMS like Xtal - Xtal C-Fiber thickness: Inside Module : 400 µm Across Module: 600 µm Very small Module Size (3x3, 5x5) effect CMS like dead material has smaller effect and module size dependency LSO crystals should have sufficient mechanical strength (under ivestigatigation) SLAC 15/02/08 LSO Cal G4 Simulation

Projectivity Module Matrix In order to have more realistic dead/active material ratio implement Projective Geometry Trapezioidal crystals Projective Beam Position fixed close to pointing distance Direction with 2D opening angle Matrix SLAC 15/02/08 LSO Cal G4 Simulation

CMS like geometry with tyvek Tyvek wrapping could improve light output (not simulated): what is the effect on CMS like geometry? Tyvek thickness similar to BaBar Effect is not negligible SLAC 15/02/08 LSO Cal G4 Simulation

CMS like: C-fiber thickness Change C-fiber thickness in CMS like geometry Change both inner and outher wall thickness As expected C-Fiber thickness affect performances E/E @ 1 GeV: 0.82 %  1.07 % (0.25 %) SLAC 15/02/08 LSO Cal G4 Simulation

Dead Material and Modularity Conclusions If LSO crystals have the needed mechanichal strength CMS like dead material has smaller effect on performances Selecting CMS like configuration modularity has small impact on performances Adding reflective/diffusive material (like Tyvek) or changing C-fiber thickness (few 100s m) in CMS like configuration has not negligible effect on performances SLAC 15/02/08 LSO Cal G4 Simulation

Upsteram Material Effect: geometry Xtals: 2.50 x 2.50 cm Front 2.88 x 2.88 cm Back Pointing distance ~ 1.5 m Matrix: 3x3 Xtals module CMS like BaBar like 7x7 module matrix Upstream material 2 configurations with several thickness Slab close to Matrix Variable thickness C-Fiber Dummy Detectors SVT: 5 x 300 m Si layers DCH: variable thickness Ar C-Fiber layers Slab Dummy SVT Dummy DCH SLAC 15/02/08 LSO Cal G4 Simulation

Deposited Energy e-,  Peak shifted (ionization loss) 1 GeV e- Electrons and photons show very different behavior No Peak shift 1 GeV  Distribution shoulder (upstream interacting  2nd component) SLAC 15/02/08 LSO Cal G4 Simulation

Edep vs Ebeam: e- beam on C-Fiber Slab rms Upstream material effect dominant at low energies Internal dead material effect dominant at high energies Transition region between 300 and 400 MeV (highlighted) SLAC 15/02/08 LSO Cal G4 Simulation

Edep vs X0: e- on Slab Material in front of BaBar ECAL ranges between 0.3 and 0.6 X0 (highligthed) CMS and BaBar like peak position shaw similar behavior BaBar like  more affected @ low Energies and large upstream material X0 Effect not negligible in 0.3-.6 X0 SLAC 15/02/08 LSO Cal G4 Simulation

Edep vs X0: e- on Slab and SVT+DCH CMS like geometry SVT+DCH have larger effect on both peak position and  Larger distance from crystal matrix: secondaries loss SLAC 15/02/08 LSO Cal G4 Simulation

Edep vs X0: e- and  beam on SVT+DCH effect of 2nd  component e- ionization loss small effect on main  distr Peak position e- show ionization loss effect Almost constant for  E Small effect on main  distribution Asymmetry (Epeak-Emean) Photons converting in upstream material affect  distribution asymmetry SLAC 15/02/08 LSO Cal G4 Simulation

Edep vs Ebeam: beam material comparison Peak position Not affected for  Big effect on low Energy e- All effects negligible at High Energy E Small effect on main  distribution Big effect on low E e- Smaller effect on High Energy e- wrt  Transition region between 400 MeV and 1 GeV (highligthed) Beam SLAC 15/02/08 LSO Cal G4 Simulation

Edep vs Ebeam:  beam on SVT+DCH Since  distrubution main component is not affected main effect on resolution is dominated by internal dead material SLAC 15/02/08 LSO Cal G4 Simulation

Edep vs X0: on SVT+DCH The effect on the  is small even with large upstream material tickness The effect on the distribution asymmetry (Epeak-Emean) is quite big with large upstream material SLAC 15/02/08 LSO Cal G4 Simulation

Upstream Material Conclusions e- and  are affected in different ways e- have a transition with energy from upstream material dominated to internal material dominated resolution  have a two components behavior the main component remains internal material dominated the 2nd component becomes important only for large upstream material thickness (> 0.1 - 0.4 X0 depending on energy) The SVT+DCH geometry seems to have bigger effect wrt the Slab one Distance effect SLAC 15/02/08 LSO Cal G4 Simulation

The work is proceeding adding geometrical details in several steps: Summary and Outlook The work is proceeding adding geometrical details in several steps: Dead Material Projectivity Effect of upstream material Next step will be define a geometry which is a subset (module) of a realistic Fwd ECAL geometry: Matrix  Rings subsets SLAC 15/02/08 LSO Cal G4 Simulation