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

Summary TG-10MC & Background

Xiang Liufor TG-10

Last Collab. Meeting

Gerda Collab. , Jun 27-29, 2005 Last Collaboration meeting

Joint MC force from Gerda & Majorana.

Generator, physics processes, material, management, etc.

mjgeometry mjio

gerdaiogerdageometry

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.

Outline

Gerda Collab. , Jun 27-29, 2005 outline

Achievement since then:

1) MaGe update

2) Gerda related: Background & Calibration sources

3) R&D related: H-M crystals, LArGe

4) Verification (Comparison) with SHIELD

5) Analysis: Pulse shape simulation & analysis

Summary & Outlook

MaGe Ready!

Gerda Collab. , Jun 27-29, 2005 1) Further MaGe development

An internal note describing MaGe is ready.

First official version soon, MaGe ready for users.

Version releasing procedure being established.

MaGe ready to answer questions from other TGs!

2) Gerda Background & Calibration

Gerda Collab. , Jun 27-29, 2005 2) Gerda Background

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

radioactive

calibration

Analysis of bkgd contributions from support structure (Phase-I)

Co-60: 1.4 ·10-4

Bi-214: 5.1 ·10-5

Tl-208: 1.4 ·10-4

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

MaGe Geant4 MC: probabilities per decay to deposit energy at Q in 1 keV energy bin

Using our limits for Cu, PTFE and SiRate in roi: <1.5·10-3 / (keV kg year)

Gerda Collab. , Jun 27-29, 2005 2) Gerda Background – radioactive bg.

Radioactive bg. (Phase-II)

Source Activity Suppr. FactorBkg. 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 1.2 ·10-4 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 1.2 ·10-4 <1

2νββ T1/2 = 1.74·1021 y < 10-6 < 0.45

K. Kroeninger, L. Pandola

800 M. Radon in water tank generated, not a issue.

Gerda Collab. , Jun 27-29, 2005 3) Gerda Calibration

Gerda Calibration Source

Source inside container

>1k events in photon peak in each segment

K. Kroeninger

60Co, 22Na and 88Y, good candidates

Summary Background & Calibration

Gerda Collab. , Jun 27-29, 2005 2) Gerda Background & Calibration

Top veto & water Cerenkov veto of cosmic muon Phase-I prefers Top veto below penthouse (4.4 10-4 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 < 2-3 10-4

Calibration source for Gerda Gerda Note ready.

3) R&D: H-M crystals & LArGe

Gerda Collab. , Jun 27-29, 2005 3) R&D

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

Simulating Hd-Mo crystals

Det. 1

0.98 kg

1 m

ANG1 ANG3

ANG4ANG2

oldnew

newC.Tomei

Gerda Collab. , Jun 27-29, 2005 3) R&D

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

Co60 comparison

Ratio of gamma lines in data locate bg source positions,

verified by MC (O. Chkvorets in TG1)

General agreement with measurement.

More to be understood.

Simulating LArGe

Gerda Collab. , Jun 27-29, 2005 3) R&D

Simple setup:Goal: complete

simulation of the scintillation photons

Surface reflection.

Scattering & absorption.

Crystal shadowing effects.

Properties of WLS.

All depend on wave-lengths!

LAr scintillation: large yield (40,000 ph/MeV) but in the UV

(128 nm)

L. Pandola

PMT

crystal

reflector and WLS

tank

Gerda Collab. , Jun 27-29, 2005 3) R&D

Optical physicsGeant4 (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

The optical properties of materials and of surfaces (e.g. refraction index, absorption length) must be implemented

often unknown (or poorly known) in UV

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

Gerda Collab. , Jun 27-29, 2005 3) R&D

Output from the simulation

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

Ar peak

VM2000 emission

Cerenkov spectrum

LArGe set-up at Gran Sasso

Number of crystals columns and plans tunable by macro

( interfaced with the general Gerda geometry tools)

Available in MaGe and ready for physics

studies

The geometry for the LArGe set-up at Gran Sasso has been implemented in

MaGeIt includes the shielding

layers, the cryo-liquid and the Ge crystals

MaGe progress:

physics validation • 2 data sets from:

– 60Co source + 168 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)

D. Franco

MaGe progress:physics validation

Ra-226 calibration of conventional crystal

Summary on LArGe Simulation

Gerda Collab. , Jun 27-29, 2005 3) R&D

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

SHIELD(JINR,1972)(Nucleons-Pi mesons cascades evolution

up to energy 20 – 30 GeV )

SHIELD(INR RAS,1989)(Kernel had been totally overwritten.

Growth of functionality)

SHIELDHI(INR RAS,1997)(Interactions of nucleons, Pi, K, anti nucleons,

muons, all (A,Z) nuclei. All isotope and chemical compounds, complex geometry)

SHIELD-HIT(INR RAS,KI,2001)(Energies at 1 TeV/A are available)

4) MaGe verification with SHIELDA. Denisov

Inelastic interactionsMSDM generator

(Multy Stage Dynamical Model.Exclusive approach. )

Low energy neutrons transportation

LOENT (ABBN 28 constants)

GeometryImproved CG module

(Combinatorial geometry)

SHIELD is transparent

MaGe

Energy transfer spectrum from muon to hadron shower

SHIELD

Simulation of simple geometry for hadron transportation

MaGe

Comparing with Bugaev - Bezrukov formula

Comparing results and analyzing discrepancies

Proposed comparison

5) Pulse shape simulation & analysis

Gerda Collab. , Jun 27-29, 2005 5) Pulse Shape

Co60

Kevin Kroeninger

Pulse shape simulation

Gerda Collab. , Jun 27-29, 2005 5) Pulse shape

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

Drifting field

Gerda Collab. , Jun 27-29, 2005 5) Pulse shape

• Example: true coaxial n-type detector

Holes

Electrons

Electrons Holes

Local energydeposition

Weighting field

Gerda Collab. , Jun 27-29, 2005 5) Pulse shape

(Slices in z showing x-y plane)

z = 5.1 cm z = 7.7 cmz = 2.6 cm

y

zIMPORTANT: Particles do not move

due to weighting field

• Example: true coaxial detector with 6 φ- and 3 z-segments

Pulse Shape simulated

Gerda Collab. , Jun 27-29, 2005 5) Pulse shape

• Full simulation of true coaxial 6-fold segmented detector

electrode electrode electrode

electrode electrode electrode

core

Cha

rge

Time

Rising time

R

Left-right asymmetry

Rising time comparison

Gerda Collab. , Jun 27-29, 2005 5) Pulse shape

Risetime [ns]

Pulse Shape analysis “Mexico hat”

Gerda Collab. , Jun 27-29, 2005 5) Pulse shape

• Examples of mexican hat filter for different widths

Distinguish power to some extent

Summary on Pulse Shapes “R&D”

Gerda Collab. , Jun 27-29, 2005 5) Pulse shape

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!

Gerda Collab. , Jun 27-29, 2005 summary

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 Outlook

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

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)