1. Institut für Kernphysik Markus Horn ILIAS-N3, BSNS-working group meeting Valencia, 15.04.2005 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Institut für Kernphysik EDELWEISS II muon veto, Geant4 physics, muon induced neutrons, muon-nuclear interaction, summary & discussion GEANT4 – Simulations of muon-induced neutrons for the Experiment

2. Valencia, 15.04.2005Markus Horn: GEANT4 – Simulations of muon-induced neutrons EDELWEISS II – muon veto system 10/2005:21×320g Ge/NTD thermistor 7 ×400g Ge/NbSi ‘thin film sensors’ sensitivity goal: ×100 EDWI (1kg)  EDWII (40kg)  ’total exposure’ ×100  neutron background (E recoil > 30 keV) main source: muon-induced neutrons from rock and shielding EDW-IEDW-II 0.5 evt (30.5 kg ×d) 50 evts (3000 kg ×d) muon veto system

3. Valencia, 15.04.2005Markus Horn: GEANT4 – Simulations of muon-induced neutrons EDELWEISS Geant4 – background simulations Tasks: 1.Implement energy and angular distribution of muon flux in underground lab (LSM, Fréjus mountain) 2.Deep Inelastic Scattering (DIS) of high energy muons in rock and shielding material 3.Test & understand Geant4 `muNucl` interaction (energy & angular distribution) 4.Comparison of Geant4 with G3, FLUKA, MCNP, etc. (  `benchmarks`) 5.Neutron tracking in the detector area and the surrounding

4. Valencia, 15.04.2005Markus Horn: GEANT4 – Simulations of muon-induced neutrons Geant4 7.0 physics list Inelastic models used: Muon-photonuclear >1GeV Photonuclear < 3GeV QGSP (>12GeV): high energetic hadronic interaction incl. pre-equilibrium-cascade model, nuclear evaporation & multi-fragmentation BiC (<6GeV): intra-nuclear binary cascade model Neutron-HP (<19MeV): data- driven model  details s.a.Geant4- Collab. neutrons HP250 keV< E <19.9 MeV PreCo19.5 MeV< E <70 MeV BiC65 MeV< E <6.1 GeV LEP6 GeV< E <12.1 GeV QGSP12 GeV< E <100 TeV protons PreCo250 keV< E <70 MeV BiC65 MeV< E <6.1 GeV LEP6 GeV< E <12.1 GeV QGSP12 GeV< E <100 TeV π /K/ions BiC 250 keV< E <1.5 GeV LEP 1.4 GeV< E <12.1 GeV QGSP 12 GeV< E <100 TeV

5. Valencia, 15.04.2005Markus Horn: GEANT4 – Simulations of muon-induced neutrons Neutron yield material: C n H 2n neutron yield in relative good agreement with experimental data differences to Kudryavtsev et al. (hep-ex/0411026) –Why 15% lower yield ?  Physics List, G4version ? –Correction of yield at 10GeV –MC error bars ? Statistics and systematics ? Rare events with high n-multiplicity ~2×10 5 µ(10-1000GeV), C n H 2n, 3200g/cm 2

6. Valencia, 15.04.2005Markus Horn: GEANT4 – Simulations of muon-induced neutrons Neutron multiplicity µ-ind. spallation (in most cases only once per event) produces few hadrons secondary neutrons by hadronic showers on average 4-5 neutrons per event maximum multiplicity  ~100 -1000 (depending on material and energy, e.g. Pb, E µ =1TeV) ~2×10 5 µ(280GeV), C n H 2n, 3200g/cm 2

7. Valencia, 15.04.2005Markus Horn: GEANT4 – Simulations of muon-induced neutrons Muon induced neutrons >10 5 µ(10-1000GeV), C n H 2n, 3200g/cm 2 material: C n H 2n deep inelastic muon- nucleus interaction via virtual photon photonuclear reactions in el.-m. showers triggered by incident muon secondary neutron production (π-N, π-absorption, p-N, etc.)

8. Valencia, 15.04.2005Markus Horn: GEANT4 – Simulations of muon-induced neutrons Diff. energy spectrum of neutrons material: C n H 2n muon energy: 280 GeV LVD exp. data (measurement in GranSasso- underground lab) scaled (x6)  neutron detector efficiency good agreement with FLUKA simulations (Kudryavtsev et al. hep-ex/0411026) ~10 5 µ(280GeV), C n H 2n, 3200g/cm 2

9. Valencia, 15.04.2005Markus Horn: GEANT4 – Simulations of muon-induced neutrons Neutron yield in different materials materials: –C n H 2n, –Fréjus & LNGS rock, –concrete, –copper, –lead muon energy: 280 GeV max. difference FLUKA ↔ Geant4 less than factor ×2 ~10 5 µ(280GeV), 3200g/cm 2

10. Valencia, 15.04.2005Markus Horn: GEANT4 – Simulations of muon-induced neutrons Muon-nucleus interaction I energy transfer of muon-nucleus interaction (`muNucl´) E E´ E trans ~2×10 5 µ(280GeV), C n H 2n, 3200g/cm 2 280GeV 200MeV

11. Valencia, 15.04.2005Markus Horn: GEANT4 – Simulations of muon-induced neutrons ~2×10 5 µ(280GeV), C n H 2n, 3200g/cm 2 Muon-nucleus interaction II - muons angular distribution of muon-nucleus interaction (`muNucl´) µ θ µ´

12. Valencia, 15.04.2005Markus Horn: GEANT4 – Simulations of muon-induced neutrons Muon-nucleus interaction III - neutrons kinetic energy distribution of `muNucl´- neutrons µ µ´ E neutron sec. particles n ~2×10 5 µ(280GeV), C n H 2n, 3200g/cm 2

13. Valencia, 15.04.2005Markus Horn: GEANT4 – Simulations of muon-induced neutrons Muon-nucleus interaction IV - neutrons angular distribution of muon-nucleus interaction (`muNucl´) µ θ µ´ sec. particles n E neutron ~2×10 5 µ(280GeV), C n H 2n, 3200g/cm 2

14. Valencia, 15.04.2005Markus Horn: GEANT4 – Simulations of muon-induced neutrons Muon-nucleus interaction V - neutrons

15. Valencia, 15.04.2005Markus Horn: GEANT4 – Simulations of muon-induced neutrons differences to Kudryavtsev et al. (hep-ex/0411026) : –Due to slightly different physics list ? Or G4 version ? –How to correct neutron yield for 10GeV muons ? (  benchmarks) neutron multiplicity and statistics Muon-nucleus interaction: –Why minimum energy transfer of 200MeV ? –Why 1keV – line in neutron spectrum ? –Why backward peak in angular distribution ? (Problems with G4 core dump - G4Fragment: pi ± ) Open questions benchmarks ( ) µ - DIS

16. Valencia, 15.04.2005Markus Horn: GEANT4 – Simulations of muon-induced neutrons Muon yield and detector geometry Tasks: 1.Energy distribution and angular distribution of muon yield corresponding to geography 2.n-tracking in detector(-area)  full detector geometry has to be implemented m