Energy spectra and particle distributions in BeamCal at the ILC

1. Energy spectra and particle distributions in BeamCal at the ILC Eliza Teodorescu FCAL Collaboration Meeting May 6-7, 2008, Krakow, Poland

2. Overview BeamCal - characteristics Specifics of my work: Geometry implementations Physics lists Results pairs and gammas energy depositions kinetic energy neutrons distributions fluence Future plans Summary

3. BeamCal characteristics BeamCal BeamCal will be hit by a large amount of electron-positron pairs stemming from beamstrahlung efficiently detect single high energetic electrons at lowest polar angles, important for particle searches shield the Inner Detector against backscattering from beamstrahlung pairs the spatial distribution of the energy deposition from beamstrahlung pairs contains a lot of information about the collision use a fast algorithm to extract beam parameters to improve the accelerator parameters

4. Simulate Collision: Guineapig(nominal parameter set) photon/pair ASCII File Simulate detector: BeCaS1.2 full GEANT4 simulation => energy, particle distributions … ROOT file The simulation chain OUTPUT INPUT OUTPUT • BeCaS • A Geant4 BeamCal simulation (A.Sapronov) • Can be configured to run with: • differentcrossing angles (corresponding geometry is chosen): here: 14 mrad • magnetic field(solenoid, (Anti) DID, use field map): here: Anti DID

5. Suport tube (Iron) Absorber (W) Electronics Sensor Dead Area 30 X0 Ri Ro Re RTo Specifics of my work sandwich em. calorimeter: • 30 layers of 1 X0 • 3.5mm W + 0.3mm sensor • ~ 104 - 105 channels of ~0.8 RM • ~ 20mm < R < 165mm (175 electronics 225 suport tube) • each sensor layer divided into 8 sectors Ri = 20 mm R0 = 165 mm Re = 10 mm RTi = 175 mm RTo = 225 mm RTi

6. Specifics of my work In Geant4, the user has to specify: particles, processes, production cuts Mandatory and critical user’s task ! This implies defining all the physics to be used in his simulation physics lists Physics List - a set of consistent physicsmodels for each particle in application according to user’s needs Making (or using) correct and proper physics list is user’s responsibility electromagnetic physics - relatively simple and standard hadronic physics - complex, and depends on the particular application domain the user is interested in Geant4 provides some defaultphysics lists

7. Specifics of my work For my purpose : 2 physics lists • Custom physics list • QGSP_BERT_HP physics list Task: Comparison between results from different physics lists Input file : 5 bunch crossings (380 000 events)

8. Specifics of my work EM Physics each process -> 1 model (QED) -> 1 cross section

9. Specifics of my work Processesfor both physics lists: For gamma : • gamma conversion • compton scattering • photo-electric effect • photo-nuclear process <- models: Low energy : G4GammaNuclearReaction High energy : G4TheoFSGenerator G4GeneratorPrecompoundInterface (transportation) fragmentation: G4QGSMFragmentation () G4EcitedStringDecay G4QGSModel

10. Specifics of my work For electron and positron • multiple scattering • ionisation • bremsstrahlung • annihilation (for e+) • electron/positron nuclear processes • model :G4ElectronNuclearReaction Differences CustomPhysicsList-> additional option for low energies (< 100 KeV): - e+e- - gamma Low Energy Rayleigh Process for low energy photons Low Energy Compton Low Energy Gamma Conversion Low Energy Ionisation Low Energy Bremsstrahlung QGSP_BERT_HP:adds the synchrotron radiation process using: G4SynchrotronRadiation()

11. Results

12. Kinetic energy for gamma Custom Physics List QGSP_BERT_HP

13. Energy deposition for e+e- as a function of the layer depth Custom Physics List QGSP_BERT_HP

14. Energy deposition for e+e-, for a specific layer Custom Physics List QGSP_BERT_HP

15. Kinetic Energy for e+e- as a function of the layer depth Custom Physics List QGSP_BERT_HP

16. Kinetic Energy for e+e-, for a specific layer Custom Physics List QGSP_BERT_HP

17. Radial Energy Deposition for e+e- Custom Physics List QGSP_BERT_HP

18. Conclusion For electromagnetic processes we obtain similar results using these two physics lists

19. Hadronic Physics 1 process -> many possible models -> many cross sections A process uses cross sections to decide when and where an interaction will occur uses an interaction model to generate the final state For each process – default cross sections some contain only a few numbers to parametrize cross section some represent large databases Hadronic processes At rest stopped mu, pi, k, anti-proton radioactive decay Elastic same process for all long-lived hadrons Inelastic Different process for each hadron it includes the photo- and electro-nuclear process Capture Fission

20. Hadronic processes and models for both physics lists (for neutrons) Processes : Elastic Scattering (G4HadronElasticProcess) • Models: • G4LElastic • - use of high precision models for low energies (< 20 MeV) (option for Custom) • - using G4NeutronHPElasticData Inelastic Scattering (G4NeutronInelasticProcess) • Models: • G4LENeutronInelastic • - use of high energy neutron inelastic model (option for Custom) • - use of high precision inelastic model for neutrons (< 20 MeV) (option) • - using : G4NeutronHPInelasticData Neutron Capture (G4HadronCaptureProcess) • Models: • G4LCapture • - use of Neutron High Precision Capture (< 20 MeV) (option only for Custom) • - using G4NeutronHPCaptureData

21. Differences The QGSP_BERT_HP includes also: Inelastic Scattering Models : G4CascadeInterface using G4TheoFSGenerator: Bertini cascade model (transportation) G4GeneratorPrecompoudInterface in which: de-excitation: G4PreCompoundModel using: G4ExcitationHandler Quark Gluon String model (high energy generator) fragmentation: G4ExcitedStringDecay using: G4QGSMFragmentation G4CascadeInterface Neutron induced fission Model: G4LFission

22. Results

23. Neutron Kinetic Energy as a function of the layer depth Custom Physics List QGSP_BERT_HP EK < 1 MeV EK > 1 MeV

24. Number of neutrons as a function of the layer depth Custom Physics List QGSP_BERT_HP EK < 1 MeV EK > 1 MeV

25. Neutron Kinetic Energy for a specific layer (5, 16, 26) Custom Physics List QGSP_BERT_HP

26. The number of neutrons in X-Y coordinates Custom Physics List QGSP_BERT_HP

27. 5bx Fluence (1/mm2) Phi (rad) Neutron Fluence for a specific ring (1, 7, 16), layer 4 Custom Physics List QGSP_BERT_HP Not more than 9-10 neutrons/mm2

28. 5bx Fluence (1/mm2) Phi (rad) Neutron Fluence in Electronics, for a specific layer (5, 16, 26) Custom Physics List QGSP_BERT_HP Less than 0.1 n/mm2

29. Future plans Further investigations on differences between physics lists • processes • cuts Obtain distributions for hadrons

30. Summary the mock-up of the read-out electronics was added to the BeCaS neutron fluence in the BeamCal sensors and electronics was simulated using Custom and QGSP_BERT_HP physics lists the physics lists produce similar distributions for electro-magnetic processes but quite different for the hadronic ones Custom physics list produces about 3 times less “low energy neutrons” than QGSP_BERT_HP and almost 1.5 times more “high energy neutrons” the results depend strongly on models we should probably give our preference to the QGSP_BERT_HP physics list, it simulates more proceses and makes use of more models