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