Summary of dE/dx studies in silicon and MS in muon system with different Gauss versions  G4 7.1, 8.2 and 8.3 07 Feb. 2008

History Known for a long time that energy loss in Si in Gauss is wrong ST solution: use own model But problem remains for Velo + tracking G4 7.1.patch01a

History DC 06 (G4 7.1.patch01a) G4 Fast summer (G4 8.2..patch01 EMV) G4 Def summer (G4 8.2.patch01 Std) Now (Gauss v30r4, G4 8.3.patch01 EMV) Version of Geant 4 used in the summer dE/dx reduced Difference between fast and standard settings Question-mark whether Geant4 was using our tracking settings Velo tracking efficiency went down but dp/p better by 10 % New version dE/dx increased and also Velo tracking efficiency i.e. our tracking cuts seemed to be ignored with 8.2 ADC threshold

Tuning Strategy Many parameters that can be tuned in Geant4 Big to stop -rays production Kinetic energy cuts Range cuts Important to tune the parameters consistantly Standard energy cut settings -rays range > 5mm If track down to 100 keV for electrons -ray range 100 micron 1 MeV -ray have range ~1 mm Range of 100 keV Electron is ~ 100 micron Bichsel 1990 Brigida 2004

Particle Gun Studies Fast studies of energy loss with a Particle gun Gauss v30r4 (G4 8.3.p01), Boole v30r6 Scan Geant settings: fast versus standard, -ray range Generate samples of 50k muons at fixed energy I am sure Geant is taking our tracking settings Only simulate VELO to save speed Previous studies show results are applicable to ST Plot deposited energy in Si Extract MPV value from parabola fit around maximum FHWM by linear interpolation around ~ half height points

Particle Gun Studies Want to count all the energy deposited by muon in Si Primary + -rays Most robust algorithm is to count all energy deposited in sensor Only works because I have a single particle gun Find some energy is ‘lost’ if cut settings not consistent Choice of settings is important ! Standard energy thresholds Range for -rays 1 micron Lower energy thresholds

Particle Gun: Results Energy loss with new version of Gauss much closer to expectations even without -rays Why is not clear… No difference between standard and fast settings Different to studies in the Summer Use only fast from now on Gauss 24-25 series  G4 7.1-patch01a Gauss v30r4  G4 8.3-patch01 Summer  G4 8.2-patch01

Particle Gun: Results Turn on -rays shape of distribution versus  become closer to expectation from Landau theory Results independent of -rays range cut for values between 0.001 mm and 5 mm Gauss v30r4  G4 8.3-patch01

Particle Gun: Results The with of the distribution is still underestimated Add smear for the atomic binding things look more reasonable. But… Gauss 24-25 series  G4 7.1-patch01a Gauss v30r4  G4 8.3-patch01

Particle Gun: Results Smear increases the MPV Counter this by scaling by ~ 6 % Better: scale as function of 

Delta ray properties Properties of delta rays (120 GeV sample) Spectrum looks too(?) hard (4 MeV MPV, long tail to 100 MeV) Rate is suprising high 9480/651120 incident primaries ~0.014 Is this correct ? Max energy transfer in single collision (relativistic kinematics) Em = Mc2 2/[(M/2m) + 2m/M + )] At high energy practically unbounded For 500 MeV muons, limit 21 MeV Geant4 gets this correct Rate 5675/650000 ~ 0.9 %

Particle Type dependence Differences for different particle types Electrons, muon and hadrons behave differently Energy loss 5 % higher for electrons than hadrons This is not physical Suggests differences due to different physics lists/threshold settings for different particle types Again different -rays on/off Different tuning/particle type -rays off  -rays on

Minimum Bias Data 2.8 GHz Opteron processor 4 samples of 1000 events generated: Run Sim event size Time/event N No -rays , 10 MeV cut for hadrons, 1 MeV for electrons 350 k (Gauss) 126 k (Boole) 21 s 270 ms LT No -rays, 1 MeV cut for hadrons, 0.1 MeV for electrons 400 k (Gauss) 130 k (Boole) 29 s 300 ms D 5 mm range cut, 10 MeV cut for hadrons, 1 MeV for electrons 372 k (Gauss) 133 k (Boole) 24 s 290 ms LTD 0.1 mm range cut, 1 MeV cut for hadrons, 0.1 MeV for electrons 572 k (Gauss) 160 k (Boole) 43 s 410 ms From the previous discussion, results with low thresholds have large systematic errors

Multiple scattering in Muon system Special production with very low thresholds (range and tracking) and {LHEP/QGSP}_BERT_HP to make parametrization of low energy and slow background to apply during digitization for massive productions

Multiple Scattering simulation Muon trajectories are dominated by multiple scattering interaction in the Calorimeters and in the Muon Filters. In GEANT8.0 Multiple Scattering simulation was not correctly simulated in the cases of dense materials and large step sizes (like Muon filters) Correlation between displacement and angular deviation was not included.

Multiple Scattering Simulation After calorimeters After Muon Filters Red = PDG, black = Gauss (GEANT 7.1.p01a) muons p=[5-100]GeV/c (particle gun)

New Gauss v30r2 (GEANT8.2) Revised description of MS Different option file tested so far (with muons) NO improvements with “standard options”. Ok if deltaRays production enabled in MuonFilters Further investigation needed (check other particles) EMPhysics (new default) EMfastPhysics EMPhysics+ deltaRays in Mfilters

Multiple Scattering Simulation GEANT 7.1.p01a thin line = gauss; thick line = PDG M2: gauss > PDG; M3,M4,M5 gauss < PDG GEANT 8.2 EMPhysics+ deltaRays in Mfilters Nice agreement