luciano pandola, infn gran sasso luciano pandola infn gran sasso valencia, april 14 th, 2005 geant4...

Luciano Pandola, INFN Gran Sasso

Luciano Pandola

INFN Gran Sasso

Valencia, April 14th, 2005

Geant4 and the underground physics

community


What is ?What is ?

OO Toolkit for the simulation of the interaction of particles with OO Toolkit for the simulation of the interaction of particles with mattermatter– physics processes (EM, hadronic, optical) cover a comprehensive

set of particles, materials and over a wide energy range– it offers a complete set of functionalities (tracking, geometry,

hits)– born for the HEP community, but extensively used also in

medical physics, astroparticle physics and space applications

It is also an experiment of distributed software production and managementdistributed software production and management, as a large international Collaborationlarge international Collaboration with the participation of various experiments, labs and institutes

Has been creating exploiting a rigorous software engineering rigorous software engineering and Object Object Oriented technologies, Oriented technologies, implemented in the flexible C++ language


Where does it come from?Where does it come from?Where does it come from?Where does it come from?

Very high statistics to be simulated – robustness and reliability for large scale production

Exchange of CAD detector descriptions– very complex geometries and experimental setups

Transparent physics for experimental validation – possibility to use alternative/personalized physics models

Physics extensions to high energies– LHC, cosmic ray experiments

Physics extensions to low energies– space science, astrophysics, medical physics, astroparticle physics


Uniform treatmentUniform treatment of electromagnetic and hadronic processes

Abstract interfaceAbstract interface to physics processes

– Tracking independent from physics

Distinction between processes and modelsprocesses and models– Often multiple models for the same physics process (complementary/alternative)

Users can choose those that best match their needs (energy range, precision vs. CPU time)

Open system– Users can easily create and use their own models

Transparency– Calculation of cross-sections independent from the way they are accessed (data files, analytical

formulae etc.)– Distinction between the calculation of cross sections and their use– Calculation of the final state independent from tracking

PhysicsPhysicsPhysicsPhysics


Physics class structurePhysics class structurePhysics class structurePhysics class structure

Only production cuts for e- and ’s are

used

all particles tracked until

they stop

Drawback: difficult to choose the most suitable process (some lack of documentation, exp. for hadronic models) black box approach

Advantages: very flexible, multiple alternative (user-defined) models


User requirements & validationUser requirements & validationUser requirements & validationUser requirements & validation

Geant4 is open to user requirements concerning new capabilities and physics models

http://pcitapiww.cern.ch/asd/cgi-bin/geant4/urd/Problems:

- manpower (usually short)

- specific expertise needed

- modular development (some groups are more active than others)...

Geant4 was born at CERN so it was mainly “tuned” and

developed by people working in the accelerator groups

well-established MC, validation from test-beams of the experiments

Events

/10

nA

Events

/10

nA

-100-100 10010000 200200 300300 400400 50050000

600600

100100200200

300300400400500500

700700800800

Calorimeter Signal [nA]Calorimeter Signal [nA]

180 GeV μ



Geant4 became a well-established “reference” Monte Carlo also in other sectors medical physics

15x15 cm2

15x15 cm2

Differences

e.m. Physics Geant4-05-00

Depth dose and profile curves for clinical x-ray beams

Bragg-peak of 60-MeV protons

for cancer therapy

Require accuracy of EM processes (LowE)


Physics Validation Physics Validation

SystematicSystematic and extensive validationextensive validation of the whole physics content is fundamental in Geant4

Specific validations at different levels

MicroscopicMicroscopic physics validation of each modelof each model cross section, angular/energy distributions

MacroscopicMacroscopic validation with experimental use cases full simulation of experimental set-ups

necessary stage to guarantee reliable simulations

The results of simulations must be quantitatively compared with established and authoritative

reference data experimental measurements on refereed journals and/or open standard dabatases (ICRU, NIST, Livermore)



Geant4 EM physics models (“standard” and “low energy”) are being validated in a systematic and quantitative way

Data: Shimizu et al, Appl.

Phys. 9 (1976) 101Al slab

E = 20 keV

1040 nm

320 nm

electron transmission

G4Standard

G4 LowE

NIST

G4 LowE

Data

electron backscatteringphoton attenuation

K. Amako et al., Validation of Geant4 electromagnetic physics versus the NIST databases, submitted to IEEE Trans. Nucl. Scie.



(My feeling) Geant4 is still not considered a fully established and trustworthy Monte Carlo in the underground physics community

The medium-term goal of the G4 Collaboration is to improve this situation, consistently with the available manpower.

• small overlap between the Collaboration and the experiments ( = 3)

• no test-beams available, so validation much more complicated

• requires extensions to High Energy (e.g. muons) and to Low Energy (e.g. fluorescence) typically “decoupled” in the modular development of Geant4

Effort for a more complete validation plan (what are the priorities?). Needs strong connection with experimental and MC groups of the experiments (= us), also for providing data!


What do we need ? (my What do we need ? (my collection...)collection...)What do we need ? (my What do we need ? (my collection...)collection...)

High energy muons interactions & showers:

• neutron and hadron production (critical for DM experiments)

• isotope production

Low energy electromagnetic extensions:

• precise tracking of low-energy leptons and hadrons

• more precise energy and angular spectra

• atomic de-excitation (e.g. fluorescence x-rays)

Other:

• very precise decay schemes for Radioactive decay (low-branching channels)

• EC decay (with fluorescence) Other decays (e.g. spont. fission)

has ever been validated or cross-checked?


Low energy EM extensionsLow energy EM extensionsLow energy EM extensionsLow energy EM extensions

Geant4 provides dedicateddedicated Low EnergyLow Energy EM models electrons, positrons and gammas down to 250 eV

Based on EPDL97, EEDL and EADL evaluated data libraries

shell effects

neutrino/dark matter experiments, space and medical applications

Possible thanks to the OO-OO-oriented technologyoriented technology used

in Geant4

The whole physics content of the Penelope Monte Carlo codePenelope Monte Carlo code has been

re-engineered into Geant4

New complete set of alternative and dedicated

low energy EM physics models (atomic effects

included)

processes for photons: release 5.2, for electrons: release 6.0

Att

enuati

on

coeff

. (c

m2/g

) NIST data

Penelope

Hadron, anti-proton and ion models


A few examples of applications...A few examples of applications...A few examples of applications...A few examples of applications...

Double beta decay 76Ge experiment (GERDA & Majorana):

common parts (e.g. generators, physics, other tools) not duplicated

OO toolkit based on Geant4 (MaGe)

Flexible enough to allow

experiment-specific parts (geometry, i/o)

Preliminary physics studies:

background from outside and from structures (ropes, contact) efficiency

of segmentation/anticoincidence

background from cosmic ray muons



Preliminary results:

76Ge 02 region

Cosmic ray muons

Achievable for and cosmic ray (with dedicated veto):

Fission, (,n) and cosmogenic neutrons are not an issue

(very different for DM expts)

mainly from EM showers physics reliable

physics reliable? (with the proper physics list) work in progress

from DM groups

Goal 10-3-10-4 counts/keV·kg·y @ Q

Isotope production not an issuereliability unknown we plan

to cross-check with Fluka



Small (stupid) application derived from studies of environmental radioactivity from rocks and sands

Geant4 (LowE EM) can reproduce very well the results of a calibration with a 60Co source (in presence of the sample)

detectorsample

source

it works very well in this regime

simulation

datasimulation

data



Dark matter experiment (ZEPLIN 3):

Code from A. Howard and H. Araujo.

Released as an advanced example of Geant4



Experiment backgroundsinternal detector radioactivityrock radioactivity-induced neutron productionshielding and veto systems

CalibrationNeutronsGammas

OpticsPhoton generationLight collection studies

Detector responseScintillationIonisation(thermal)

Simulated DataVisualisationRun-time analysisInput to data analysis software

G4 is uniquely suited for integrated simulations of Dark Matter detectors



Electric fields1.1. Ionisation extractionIonisation extraction

2.2. Drift in liquid xenonDrift in liquid xenon

3.3. Extraction to gasExtraction to gas

4.4. Drift in gasDrift in gas

5.5. Luminescence lightLuminescence light

Light collection maps


Our priorities for validationOur priorities for validationOur priorities for validationOur priorities for validation

Suggestions from Prague meeting forwarded to the G4 Collaboration

Validation is this field is a difficult task close collaboration required with MC and experimental groups

• Production of -induced neutrons in high-Z materials

• Propagation of Low Energy neutrons (up to a few MeV)

• Inelastic scattering of neutrons

• Interactions of high-energy muons

• Isotope production

comparison with FLUKA, experimental data

comparison with MCNP, experimental data

comparison with other codes t.b.d.


ConclusionsConclusionsConclusionsConclusions

Present ILIAS activity of cross-check and comparison between different Monte Carlo codes is very welcome

Open a link between the Geant4 Collaboration and the experimental groups working in underground physics ( & ILIAS)

Geant4 Collaboration willing to address the requests (expecially for validation) coming from our community

A lot of work!

Requires constant feedback and support from the experimental groups

Validation & cross-check should be done in synergy


The validation of Geant4

luciano pandola, infn gran sasso luciano pandola infn gran sasso valencia, april 14 th, 2005 geant4...

Documents

astroparticle physics

medical physics

physics models http

matter physics processes

models distinction

multiple models

tracking physicsphysics

use calculation