Geant4 Electromagnetic Physics for HEP Applications

Transcription

1 Geant4 Electromagnetic Physics for HEP Applications 1 st Geant4 User Workshop University of Wollongong April 2011 Vladimir Ivanchenko, CERN On behalf of Geant4 electromagnetic standard working group

2 Outline EM physics for HEP Testing suite for EM physics HEP calorimetry Apply Cuts option Silicon Vertex Detectors Multiple scattering for muons and hadrons High Energy Models Bremsstrahlung Summary 12/9/2009 EM Physics for HEP 2

3 EM Physics for HEP EM physics simulation is traditionally an important part of HEP experiments LHC scale for mass of discovered particles depending on simulation quality Particle ID quality also depend on EM processes simulation 12/9/2009 EM Physics for HEP 3

4 HEP requirements for Geant4 Geant4 is the main simulation engine for Monte Carlo production for ATLAS, CMS, LHCb ALICE has interest Main requirements for Geant4: Robustness - stable run for billions of events in complex geometry Predictive power should not provide extra biases to simulation results Stability the same results for different Geant4 versions Flexibility introduction of new models and feature by request of HEP community Is it possible to fulfill this? In part yes - by extensive validation efforts 12/9/2009 EM Physics for HEP 4

5 Geant4 EM physics validation Validation sequence: Developer private tests Low and medium statistic tests with control of basic numbers High statistic tests by EM and hadronic groups User validation (LHC test-beams, others) Reference Physics Lists are required for regular validation Main efforts of EM groups in validation versus specific data and evaluated data sets regression tests versus previous version of Geant4 Long process required manpower 12/9/2009 EM Physics for HEP 5

6 Physics validation framework Geant4 physics groups establish several layers approach for validation Overall number of plots in complete validation run now exceed (EM + hadronics) 12/9/2009 EM Physics for HEP 6

7 HEP calorimetry 12/9/2009 EM Physics for HEP 7

8 ATLAS type calorimeters ATLAS barrel type ATLAS HEC type Visible energy increased in 9.4 by 0.5%, main contribution msc model EMV option old MSC model (g4 7.1) provided biased results 12/9/2009 EM Physics for HEP 8

9 Apply Cuts option 12/9/2009 EM Physics for HEP 9

10 ApplyCuts option in PbWO 4 CMStype Crystal Calorimeter EMX enable ApplyCuts Energy deposition is more sensitive to the value of cut Limit is 3 mm 12/9/2009 EM Physics for HEP 10

11 ATLAS barrel type calorimeter EMX Apply Cuts option enabled 12/9/2009 EM Physics for HEP 11

12 Why strong cut dependence? PDG plot Strong dependence of cross section on gamma energy No energy leak via boundaries for cuts > 1 mm for major solid media Cut(mm) Cut γ (kev) Cut e- (MeV) Cuts for Iron /9/2009 EM Physics for HEP 12

13 Comments on Apply cuts option Using Apply cuts option saves approximately 20% CPU for CMS production It is potentially dangerous to use for very high cut > 1 mm (biased results) It is useless if cut << 1 mm 12/9/2009 EM Physics for HEP 13

14 Vertex detector response 12/9/2009 EM Physics for HEP 14

15 Landau Shape of Silicon Detector Response 12/9/2009 EM Physics for HEP 15

16 Validation of Geant4 simulation of response of thin (300 um) Silicon detector F.Dupertuis, CERN summer student, /9/2009 EM Physics for HEP 16

17 Recent validation of Geant4 simulation of response of thin (300 um) Silicon detector F.Dupertuis, CERN summer student, /9/2009 EM Physics for HEP 17

18 Multiple scattering for muons and hadrons 12/9/2009 EM Physics for HEP 18

19 New WentzelVI model J. Phys: Conf. Ser. 219 (2010) Is much simpler, but fully theory based Wentzel differential cross section with mass, spin and form-factor corrections Separate, original step limitation Angular limit between the single and multiple scattering is selected dynamically, depending on momentum and step size May be applied for transportation in vacuum or low-density media Can be used together with the hadron elastic scattering process SNA+MC2010 Geant4 EM physics 19

20 MuScat test results for 9.4beta Improved area Urban model MuScat data D.Attwood et al., NIM B251 (2006) 41 WentzelVI model SNA+MC2010 Geant4 EM physics 20

21 New test of high energy MSC O.Dale - CERN summer student 2010 All models consistently predicts results width of central part of scattering 12/9/2009 EM Physics for HEP 21

22 Simulation of tails of scattering Urban model overestimates tail, WentzelVI and Colomb scattering models are in agreement with the data Become default for Geant /21/2010 Geant4 EM physics 22

23 High energy models 12/9/2009 EM Physics for HEP 23

24 List of specific high energy processes/models Relativistic bremsstrahlung with Landau- Pomeranchuk-Migdal (LPM) effect Hadron induced bremsstrahlung Relativistic gamma conversion with LPM effect Radiative corrections to muon ionisation Ionisation process for magnetic monopole Transition radiation Gamma convertion into muon pair Positron annihilation into muon pair Positron annihilation into hadrons 12/9/2009 EM Physics for HEP 24

25 New relativistic bremsstrahlung model (A.Schaelicke, IEEE-NSS 2008) Bethe-Heitler formula with corrections Complete screening with Coulomb correction Valid for E > 1 GeV Density & LPM- Effect consistent combination a la Ter- Mikaelian 287 GeV e - at Ta target (4%X 0 ) LPM 9.1 LPM 9.2 LPM off Data from the CERN experiment: H.D.Hansen et al, PR D 69, (2004) 12/9/2009 EM Physics for HEP 25

26 Comments instead of summary Since day first of LHC running for physics Geant4 simulation demonstrates a very good agreement with the data Statistic is growing and number of issues appears, in particular, for EM physics New challenges for Geant4 EM Diverse requirements to speedup simulation and increase precision 12/9/2009 EM Physics for HEP 26

27 Thank you for your attention! 12/9/2009 EM Physics for HEP 27