Geant 4 Standard Electromagnetic Physics Package Geant 4

Geant 4 “Standard” Electromagnetic Physics Package Geant 4 Standard EM group MC 2005 Chattanooga, Tennessee, USA 17 -21 April 2005 M. Maire, MC'2005 G 4 Standard EM

Geant 4 Standard EM group H. Burkhardt, V. M. Grichine, P. Gumplinger, V. N. Ivanchenko, R. P. Kokoulin, M. Maire, L. Urban BINP, Novosibirsk, Russia CERN, Geneva, Switzerland ESA, Noordwijk, The Netherlands LAPP, Annecy, France LPI, Moscow, Russia MEPh. I, Moscow, Russia RMKI, Budapest, Hungary TRIUMF, Vancouver, Canada M. Maire, MC'2005 G 4 Standard EM 2

Outline ► Standard EM package ► Overview on major developments since 2003 ► Validation/comparisons ► EM Physics. Lists ► Acceptance suite ► New developments ► Conclusions M. Maire, MC'2005 G 4 Standard EM 3

Standard EM package ► Naturally continue Geant 3 EM physics ► Include a complete set of models for simulation of electromagnetic processes in the energy range from 1 ke. V to 10 Pe. V ► Includes optical photons production and transport ► Focus on HEP experiments, well applicable for instrumentation, space, and medicine studies M. Maire, MC'2005 G 4 Standard EM 4

Design iteration in Standard EM package ► Standard EM package was one of physics package working from 1 st Geant 4 release ► Created using Geant 3 expertise ► Used practically in all Geant 4 applications § LHC experiments § Space and medicine applications ► Used in production for Ba. Bar for many years ► Some architecture problems were accumulated ► In 2003 the package were redesigned ► New developments were enabled M. Maire, MC'2005 G 4 Standard EM 5

Major activities since 2003 ► Physics improvements: § Evolutions of multiple scattering model § Hadron ionization was updated § New ionization § Muon processes were updated § Updated cross section for Compton effect § Revised PAI models § New high energy processes ► Evolution in optical photons simulation ► Cut per region from G 4 5. 1 ► Model design from G 4 6. 0 M. Maire, MC'2005 G 4 Standard EM 6

Hadron/ion ionization (1) Corrected Bethe-Bloch formula for the Ekin>2 Me. V ► ICRU 49 parameterization is used for the Ekin< 2 Me. V ► Scaling relation for other hadrons/ions ► Ion effective charge is recalculated at each step of the particle and is used also for tracking in EM field ► M. Maire, MC'2005 G 4 Standard EM 7

Hadron/ion ionization (2) ► Review formula of corrections to the Bethe-Bloch ► § § § ► New M. Maire, MC'2005 C – shell correction (was asymptotic formula) G – Mott correction (new) δ – density correction F – finite size correction (new) L 1 - Barkas correction (new) L 2 - Bloch correction (new) class G 4 Em. Corrections G 4 Standard EM 8

Integral approach EM cross sections depend on energy ► Precision of interaction probability depends on step size and energy change ► Integral approach: interaction probability is sampled using integral method (MC’ 91 Proceedings) ► Integral approach allows to have any step size for ionization ► M. Maire, MC'2005 G 4 Standard EM constant integral 11

Performance comparison 5. 2/6. 2 Performance improved after design iteration ► Initialization time smaller by 2 times for complecate geometry and much more for simple geometry ► Size of EM tables smaller by 2 times or more (HARP, CMS) ► CPU per event less at least by 10% ► Higher performance for low cuts ► M. Maire, MC'2005 G 4 Standard EM Intel 2. 4 GHz 512 KB 12

Geant 4/Penelope comparison (End point of secondaries e-) 1. 25 Me. V gamma in 1 mm Si M. Maire, MC'2005 G 4 Standard EM 16

HEP Calorimetry ► G 4 5. 2 p 02 close to G 3 ► G 4 6. 2 p 02 include integral method ► G 4 7. 0 include msc modification ► Integral method for tracking and updated model of multiple scattering provide less cut dependent results M. Maire, MC'2005 G 4 Standard EM Average energy deposition in l. Ar 18

Geant 4 muon interactions ► Basic processes: § § ► Ionisation Bremsstrahlung Production of e+e. Muon-nuclear interactions Muon differential cross sections Muon production and transport in Geant 4 is available up to 10 Pe. V M. Maire, MC'2005 G 4 Standard EM 19

Verification theory/Geant 4 difference less than 5% M. Maire, MC'2005 G 4 Standard EM 21

New High energy EM processes ► EM background due to high energy EM interaction with media: ► → µ+µ- ( ~Z 2) ► e+ µ+µ- ( ~Z) ► e+ + - ( ~Z) ► Visible at LEP and High at SLC ► Of concern for linear colliders M. Maire, MC'2005 G 4 Standard EM 22

Background for linear collider Angles of muons 250 Ge. V beam High energy e+, e-, and can produce µ+µ- pair 1010 e / bunch After collimator ~ 103 µ+µM. Maire, MC'2005 G 4 Standard EM 23

User support ► Physics Reference Manual : complete description of models/sampling methods ► Extended examples : Physics. Lists, user actions, visualization, analysis tools ► Standard group support ► 12 extended/electromagnetic examples ► 1 extended/medical example ► 1 extended/optical examples ► 3 novices ► Hyper M. Maire, MC'2005 News discussions G 4 Standard EM 25

Acceptance suite for Standard EM package ► To insure stability of ► Control on summary results with time numbers: § Average energy ► To control performance deposition ► Is based on extended § Shower shape electromagnetic § Scattering angles examples ► Tests on cross sections ► G 4 Em. Calculator is an and d. E/dx interface to d. E/dx and ► Comparison of cross sections histograms (in project) M. Maire, MC'2005 G 4 Standard EM 26

New developments and plans for Standard EM package ► Predefined G 4 Elements and G 4 Materials with parameters from the NIST data base will be available in the release 7. 1 ► Gamma processes in model design ► Comparisons/validation ► Long-term prospects: ► Physics model on level of theory/experiment ► High energy extensions ► Further performance improvement ► Complete automatic acceptance suite M. Maire, MC'2005 G 4 Standard EM for all processes 27

Conclusions ► Geant 4 Standard EM package is used in production of Monte Carlo results for many years ► Recently the package has been redesigned ► Physics was extended and improved ► Performance was improved ► There are plans to extend energy range of the Standard physics M. Maire, MC'2005 G 4 Standard EM 28