1. Summary TG-10 MC & Background
Xiang Liu
for TG-10

2. Generator, physics processes, material, management, etc.
Last Collab. Meeting
Generator, physics processes, material, management, etc.
mjgeometry
mjio
gerdaio
gerdageometry
Joint MC force from Gerda & Majorana.
Detailed simulation of Gerda.
Complete event MC information.
trajectories: all particles in GEANT4 simulation.
hits: energy deposits from particles in sensitive volume.
Radioactive backgrounds, muon veto, neutron.
Quick remind of what happened last collaboration meeting.
Gerda Collab. , Jun 27-29, 2005
Last Collaboration meeting

3. Outline Achievement since then: MaGe update
Gerda related: Background & Calibration sources
R&D related: H-M crystals, LArGe
Verification (Comparison) with SHIELD
Analysis: Pulse shape simulation & analysis
Summary & Outlook
Mention that, while number 2 is still “Letter of Intent” style, that is, to produce some numbers for the Gerda proposal, the rest parts are about different programs, namely, R&D simulation, further detailed comparison and verification of MaGe, and the analysis of pulse shapes. People talked about it a lot, now we really started, and finally!
Gerda Collab. , Jun 27-29, 2005
outline

4. MaGe Ready! An internal note describing MaGe is ready.
First official version soon, MaGe ready for users.
 MaGe ready to answer questions from other TGs!
Version releasing procedure being established.
Second message that I want to deliver, namely Gerda ready for people to use.
Gerda Collab. , Jun 27-29, 2005
1) Further MaGe development

5. 2) Gerda Background & Calibration
Top scintillator veto & water cerenkov veto of cosmic muon
 C. Tomei (LNGS)
Water Cerenkov veto & optimization of PMT
 M. Knapp (Tuebingen), A. Klimenko (Dubna)
Cerenkov veto, fine tuning GEANT4 & energy threshold
 M. Bauer (Tuebingen)
Transportation shielding  S. Belogurov
Radioactive bg. (Phase I)  S. Schoenert
Radioactive bg. (Phase II)  K. Kroeninger (MPI Munich)
Ra contamination in water  L. Pandola (LNGS)
Calibration source for Gerda  K. Kroeninger
muon
First physics topic, about Gerda proposal, try to finish the background analysis for Gerda. Presentations concerning muon or muon-induced background were already presented yesterday at the plenary session, simulation for transportation shielding was mentioned in TG2. Radioactive background are almost finished now.
radioactive
calibration
Gerda Collab. , Jun 27-29, 2005
2) Gerda Background

6. Analysis of bkgd contributions from support structure (Phase-I)
MaGe Geant4 MC: probabilities per decay to deposit energy at Q in 1 keV energy bin
Co-60: 3.1 ·10-5
Bi-214: 1.3 ·10-5
Tl-208: 7.5 ·10-5
Co-60: 1.6 ·10-5
Bi-214: 1.2 ·10-5
Tl-208: 5.8 ·10-5
Using our limits for
Cu, PTFE and Si
Rate in roi:
<1.5·10-3 / (keV kg year)
Background estimations in the support for phase I estimated, Stefan schoenet presented the simulation results, which satisfied our request for Phase-I.
Co-60: 1.4 ·10-4
Bi-214: 5.1 ·10-5
Tl-208: 1.4 ·10-4

7. Bkg. Index [10-3 cnts/kg/keV/y]
Radioactive bg. (Phase-II)
K. Kroeninger, L. Pandola
Source
Activity
Suppr. Factor
Bkg. Index [10-3 cnts/kg/keV/y]
60Co (holder) ?
(0.7 – 2.4)·10-5
208Tl (holder)
9 μBq/kg
1.2 ·10-4
0.3
214Bi (holder)
25 μBq/kg
2.5 ·10-5
0.2
68Ge (crystal)
58 /kg/year
2.2 ·10-4
0.8
208Tl (surface)
80 /surface/year
0.03
210Pb (surface)
1 μBq/surface
0.6 ·10-5
0.04
60Co (cyrstal)
15 /kg/year
4.7 ·10-5
0.07
226Ra (cable)
< 26 μBq/kg
<1
2νββ
T1/2 = 1.74·1021 y
< 10-6
< 0.45
Background for Phase-II almost satisfies our request as well. We located the major background contributions.
800 M. Radon in water tank generated, not a issue.
Gerda Collab. , Jun 27-29, 2005
2) Gerda Background – radioactive bg.

8. Gerda Calibration Source
K. Kroeninger
Nothing more to say.
Source inside container
>1k events in photon peak in each segment
60Co, 22Na and 88Y, good candidates
Gerda Collab. , Jun 27-29, 2005
3) Gerda Calibration

9. Summary Background & Calibration
Top veto & water Cerenkov veto of cosmic muon
Phase-I prefers Top veto below penthouse ( cnts/kg.y.keV)
Phase-II Cerenkov veto necessary (<3 10-5)
Cerenkov veto seems efficient, more developement by A. Klimenko, M. Bauer & M. Knapp.
Radioactive background inside crystal, cable & supports
Sum: ~2 10-3, dominant: Ge68 & Co60 in crystal, Ra226 in support
expect pulse shape to help further
Ra contamination in water <
Calibration source for Gerda
 Gerda Note ready.
Gerda Collab. , Jun 27-29, 2005
2) Gerda Background & Calibration

10. 3) R&D: H-M crystals & LArGe
Simulation of existing Hd-Mo detectors & Comparison with measurement
 C. Tomei (LNGS), O. Chkvorets (MPI-K)
Simulating LArGe at MPIK & Gran Sasso (optical processes)
 L. Pandola
Compare LArGe simulation with measurement (see TG1 summary)
 D. Franco (MPI-K)
Teststands at MPI Munich (see pulse shape)
 K. Kroeninger
Many data verifications!
Gerda Collab. , Jun 27-29, 2005
3) R&D

11. Simulating Hd-Mo crystals
Det. 1
0.98 kg
old
new
ANG1
ANG3
ANG4
ANG2
1 m
new
C.Tomei
Gerda Collab. , Jun 27-29, 2005
3) R&D

12. Comparison with data Ba133
Performed by O. Chkvorets and S. Zhukov on February 2005 inside the old LENS barrack first and in LUNA 1 barrack afterwards.
Detectors shielded with 10 cm lead
Radioactive sources: 60Co and 133Ba (also 226Ra)
Gerda Collab. , Jun 27-29, 2005
3) R&D

13. Co60 comparison General agreement with measurement.
More to be understood.
Ratio of gamma lines in data  locate bg source positions,
 verified by MC (O. Chkvorets in TG1)
Gerda Collab. , Jun 27-29, 2005
3) R&D

14. Simulating LArGe L. Pandola
Simple setup:
Goal: complete simulation of the scintillation photons
PMT
crystal
reflector and WLS
tank
LAr scintillation: large yield (40,000 ph/MeV) but in the UV (128 nm)
Surface reflection.
Scattering & absorption.
Crystal shadowing effects.
Properties of WLS.
All depend on wave-lengths!
Gerda Collab. , Jun 27-29, 2005
3) R&D

15. It is complicated!! Optical physics
Geant4 (and then MaGe) is able to produce & track optical photons (e.g. from scintillation or Cerenkov)
Processes into the game:
scintillation in LAr
Cerenkov in LAr
boundary and surface effects
absorption in bulk materials
Rayleigh scattering
wavelenght shifting
Refraction index of LAr
Properties of all interfaces (reflectivity, absorbance)
Absorption length of LAr
Rayleigh length of LAr
Emission spectrum of VM2000 (measured here) and QE
The optical properties of materials and of surfaces (e.g. refraction index, absorption length) must be implemented  often unknown (or poorly known) in UV
Gerda Collab. , Jun 27-29, 2005
3) R&D

16. Output from the simulation
Ar peak
VM2000 emission
Cerenkov spectrum
Frequency spectrum of photons at the PM (to be convoluted with QE!)
The ratio between the LAr peak and the optical part depends on the WLS QE: critical parameter
Scintillation yield  40,000 ph/MeV
Gerda Collab. , Jun 27-29, 2005
3) R&D

17. LArGe set-up at Gran Sasso
The geometry for the LArGe set-up at Gran Sasso has been implemented in MaGe
It includes the shielding layers, the cryo-liquid and the Ge crystals
Number of crystals columns and plans tunable by macro
( interfaced with the general Gerda geometry tools)
Available in MaGe and ready for physics studies

18. MaGe progress: physics validation
D. Franco
2 data sets from:
60Co source g bare crystal in LN (stat: 5.2e10)
226Ra source with a 830 g conventional crystal
2 positions: in the center (statistics 8.5e7) & 60mm away (statistics 4.0e8)
LArGe-MPIK: 60Co, 226Ra, 137Cs
Three tests:
Comparison of the spectral shapes
Efficiency (# of events in a gamma peak/disintegration)
Ratio (# of events in a gamma peak/# of events in the gamma peak of reference)

19. MaGe progress: physics validation Ra-226 calibration of conventional crystal

20. Summary on LArGe Simulation
measurement
simulation
analysis presented in this talk is preliminary
Comparison limited by measurement.
but: we show that LAr suppression works
MaGe reproduces the spectra fairly well
Gerda Collab. , Jun 27-29, 2005
3) R&D

21. SHIELD-HIT(INR RAS,KI,2001)
4) MaGe verification with SHIELD
A. Denisov
SHIELD-HIT(INR RAS,KI,2001)
(Energies at 1 TeV/A are available)
SHIELDHI(INR RAS,1997)
(Interactions of nucleons, Pi, K, anti nucleons,
muons, all (A,Z) nuclei. All isotope and
chemical compounds, complex geometry)
SHIELD(INR RAS,1989)
(Kernel had been totally overwritten.
Growth of functionality)
SHIELD(JINR,1972)
(Nucleons-Pi mesons cascades evolution
up to energy 20 – 30 GeV )

22. SHIELD is transparent Improved CG module (Combinatorial geometry)
LOENT
(ABBN 28 constants)
Low energy neutrons
transportation
MSDM generator
(Multy Stage Dynamical Model.
Exclusive approach. )
Inelastic interactions

23. Comparing with Bugaev - Bezrukov
MaGe
Energy transfer spectrum from muon to hadron shower
Comparing with Bugaev - Bezrukov
formula
MaGe
SHIELD
Simulation of simple geometry for hadron transportation
Comparing results and analyzing discrepancies
Proposed comparison

24. 5) Pulse shape simulation & analysis
Co60
Kevin Kroeninger
Gerda Collab. , Jun 27-29, 2005
5) Pulse Shape

25. Pulse shape simulation
How to simulate PS:
 Calculate electric field E with given boundary & bias voltage.
Calculate “weighting field” for each segment (Ramo’s theory).
 Hits from MaGe.
 Convert hits into electron-hole pairs (1 pair per 3eV).
 electric field  Drift path.
 weighting field along path  Induced charge in each segment.
 convolute with pre-amp & DAQ effect.
Kevin Kroeninger
Explain hits: energy deposit in sensitive volume.
Gerda Collab. , Jun 27-29, 2005
5) Pulse shape

26. Drifting field Example: true coaxial n-type detector Electrons Holes
Local energy
deposition
Holes
Gerda Collab. , Jun 27-29, 2005
5) Pulse shape

27. Weighting field
Example: true coaxial detector with 6 φ- and 3 z-segments
z = 2.6 cm
z = 5.1 cm
z = 7.7 cm
IMPORTANT: Particles do not move
due to weighting field z
(Slices in z showing x-y plane) y
Gerda Collab. , Jun 27-29, 2005
5) Pulse shape

28. Pulse Shape simulated
Full simulation of true coaxial 6-fold segmented detector
electrode
electrode
electrode
Rising time R
Left-right asymmetry 
core
electrode
electrode
electrode
Charge
Time
Gerda Collab. , Jun 27-29, 2005
5) Pulse shape

29. Rising time comparison
Risetime [ns]
Gerda Collab. , Jun 27-29, 2005
5) Pulse shape

30. Pulse Shape analysis “Mexico hat”
Examples of mexican hat filter for different widths
Distinguish power to some extent
Gerda Collab. , Jun 27-29, 2005
5) Pulse shape

31. We need your experience!!
Summary on Pulse Shapes “R&D”
Data-taking:
more ways of taking single- & multi-site events?
PS simulation:
first procedure established, describes reasonably measurement
(general shapes, rising time etc).
PS analysis:
“Mexico hat” proof of principle.
All under developing!
We need your experience!!
Gerda Collab. , Jun 27-29, 2005
5) Pulse shape

32. Summary of summary MaGe in good shape.
Background under control, water cerenkov veto ongoing.
Comparison with H-M crystal measurement helps understanding bg.
LArGe simulation improved by measurement.
Verification from other MC packages, FLUKA, SHIELD
Pulse shape simulation & analysis started.
Gerda Collab. , Jun 27-29, 2005
summary

33. Group activity outlook:
LNGS: L. Pandola, C. Tomei.
Cerenkov veto, LArGe scintillation.
MPI-K: D. Franco, M. De Marco
LArGe comparison with data.
Tuebingen: M. Bauer, M. Knapp Dubna: A. Klimenko
Cerenkov veto, neutron bg.
MPI Munich: K. Kroeninger, X. Liu
Pulse shape, radioactive bg.
Moscow: A. Denisov, S. Belogurov
SHIELD improving & cross check MaGe (Geant4)
Your requests, suggestions & contributions are all welcome!
Gerda Collab. , Jun 27-29, 2005
Outlook

34. Group Members L. Pandola (Coordinator), C. Tomei (LNGS)
M. Bauer, M. Knapp (Tuebingen)
D. Franco, M. De Marco (MPI Heidelberg)
K. Kroeninger, X. Liu (MPI Munich)
A. Klimenko (Dubna)
A. Denisov, S. Belogurov (Moscow)
Gerda Collab. , Jun 27-29, 2005