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Institut für Kernphysik
ILIAS-N3, BSNS-working group meeting Valencia, 15.04.2005Markus Horn
Forschungszentrum Karlsruhein 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
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 (Erecoil > 30 keV)
main source: muon-induced neutrons from rock and shielding
EDW-I EDW-II
0.5 evt(30.5 kg ×d)
50 evts(3000 kg ×d)
muon veto system
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
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-nuclearbinary cascade model
• Neutron-HP (<19MeV): data-driven model
details s.a.Geant4- Collab.
neutrons
HP 250 keV < E < 19.9 MeVPreCo19.5 MeV < E < 70 MeVBiC 65 MeV < E < 6.1 GeVLEP 6 GeV < E < 12.1 GeV
QGSP 12 GeV < E < 100 TeV
protons
PreCo 250 keV < E < 70 MeVBiC 65 MeV < E < 6.1 GeVLEP 6 GeV < E < 12.1 GeVQGSP 12 GeV < E < 100 TeVπ
/K/ions
BiC 250 keV < E < 1.5 GeVLEP 1.4 GeV < E < 12.1 GeV
QGSP 12 GeV < E < 100 TeV
Valencia, 15.04.2005Markus Horn: GEANT4 – Simulations of muon-induced neutrons
Neutron yield
• material: CnH2n
• neutron yield in relative good agreement with experimental data
• differences toKudryavtsev 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~2×105 µ(10-1000GeV), CnH2n, 3200g/cm2
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, Eµ=1TeV)
~2×105 µ(280GeV), CnH2n, 3200g/cm2
Valencia, 15.04.2005Markus Horn: GEANT4 – Simulations of muon-induced neutrons
Muon induced neutrons
>105 µ(10-1000GeV), CnH2n, 3200g/cm2
• material: CnH2n
• deep inelastic muon-nucleus interaction via virtual photon
• photonuclearreactions in el.-m. showers triggered by incident muon
• secondary neutron production (π-N, π-absorption, p-N, etc.)
Valencia, 15.04.2005Markus Horn: GEANT4 – Simulations of muon-induced neutrons
Diff. energy spectrum of neutrons
• material: CnH2n
• 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)
~105 µ(280GeV), CnH2n, 3200g/cm2
Valencia, 15.04.2005Markus Horn: GEANT4 – Simulations of muon-induced neutrons
Neutron yield in different materials
• materials:– CnH2n,– Fréjus & LNGS rock,– concrete,– copper,– lead
• muon energy: 280 GeV• max. difference
FLUKA ↔ Geant4 less than factor ×2
~105 µ(280GeV), 3200g/cm2
Valencia, 15.04.2005Markus Horn: GEANT4 – Simulations of muon-induced neutrons
Muon-nucleus interaction I
• energy transfer of muon-nucleus interaction (`muNucl´)
E
E´
Etrans~2×105 µ(280GeV), CnH2n, 3200g/cm2
•
280GeV
200MeV
Valencia, 15.04.2005Markus Horn: GEANT4 – Simulations of muon-induced neutrons
~2×105 µ(280GeV), CnH2n, 3200g/cm2
Muon-nucleus interaction II - muons
• angular distribution of muon-nucleus interaction (`muNucl´)
µ
θ
µ´
Valencia, 15.04.2005Markus Horn: GEANT4 – Simulations of muon-induced neutrons
Muon-nucleus interaction III - neutrons
• kinetic energy distribution of `muNucl´-neutrons
µ
µ´
Eneutron
sec. particles
n~2×105 µ(280GeV), CnH2n, 3200g/cm2
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
Eneutron
~2×105 µ(280GeV), CnH2n, 3200g/cm2
Valencia, 15.04.2005Markus Horn: GEANT4 – Simulations of muon-induced neutrons
Muon-nucleus interaction V - neutrons
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