Post on 24-Dec-2015
Maria Grazia Pia, CERN/IT and INFN Genova
Electromagnetic PhysicsElectromagnetic Physics
Maria Grazia PiaCERN/IT and INFN Genova
S. Chauvie, V. Grichine, P. Gumplinger, V. Ivanchenko, R. Kokoulin,
S. Magni, M. Maire, P. Nieminen, M.G. Pia, A. Rybin, L. Urbanon behalf of the Geant4 Collaboration
Budker Inst. of PhysicsIHEP ProtvinoMEPHI Moscow Pittsburg University
MC2000 ConferenceMC2000 Conference, Lisbon, 20-23 October 2000
http://www.cerninfo.cern.ch/asd/geant4/geant4.html
Maria Grazia Pia, CERN/IT and INFN Genova
Borexinoat Gran Sasso Laboratory
HighlightsHighlights
Gamma-ray Large Area Space
Telescope
ATLAS at LHC, CERN
CMS at LHC, CERN
BaBar at SLAC
XMM
X-ray telescope
A wide domain of applications with A wide domain of applications with a large user community in many fieldsa large user community in many fields
HEP, astrophysics, nuclear physics, space sciences, medical physics, radiation studies etc.
A rigorous approach to software engineeringA rigorous approach to software engineering
Courtesy of L3Courtesy of the Italian Nat. Inst. for Cancer
Research
E (MeV)
Photon attenuation
An extensive set of physics processes and An extensive set of physics processes and models over a wide energy rangemodels over a wide energy range
High energy Low energy photons
GLAST
Maria Grazia Pia, CERN/IT and INFN Genova
Geant4 is a simulation Toolkit designed for a variety of applications
It has been developed and is maintained by an international collaboration of > 100 scientists
RD44 Collaboration
Geant4 Collaboration
The code is publicly distributed from the WWW, together with ample documentation
1st production release: end 1998 2 new releases/year since then
It provides a complete set of tools for all the typical domains of simulation
geometry and materials tracking detector response run, event and track management PDG-compliant particle management visualisation user interface persistency physics processes
It is also complemented by specific modules for space science applications
Maria Grazia Pia, CERN/IT and INFN Genova
Software Engineering
plays a fundamental role in Geant4
User Requirements• formally collected• systematically updated• PSS-05 standard
Software Process• spiral iterative approach• regular assessments and improvements• monitored following the ISO 15504 model
Quality Assurance• commercial tools• code inspections• automatic checks of coding guidelines• testing procedures at unit and integration level• dedicated testing team
Object Oriented methods• OOAD• use of CASE tools
• essential for distributed parallel development• contribute to the transparency of physics
Use of Standards • de jure and de facto
Domain decomposition
has led to a hierarchical structure of
sub-domains linked
by a uni-directional
flow of
dependencies
Geant4 architecture
Maria Grazia Pia, CERN/IT and INFN Genova
Features of Geant4 Physics OOD allows to implement or modify any
physics process without changing other parts of the software
open to extension and evolutionopen to extension and evolution
Tracking Tracking is independent from the physics processes
The generation of the final statefinal state is independent from the access and use of cross sections
Transparent access via virtual functions to
cross sections (formulae, data sets etc.) models underlying physics processes
An abundant set of electromagneticelectromagnetic and hadronic hadronic physics processes
a variety of complementary and alternative physics modelsphysics models for most processes
Use of public evaluated databasesevaluated databases
No tracking cuts, only production production thresholdsthresholds
thresholds for producing secondaries are expressed in rangerange, universal for all media
converted into energy for each particle and material
The transparency of the physics implementation contributes to the validation of experimental physics results
Maria Grazia Pia, CERN/IT and INFN Genova
multiple scattering Bremsstrahlung ionisation annihilation photoelectric effect Compton scattering Rayleigh effect conversion e+e- pair production synchrotron radiation transition radiation Cherenkov refraction reflection absorption scintillation fluorescence Auger (in progress)
Electromagnetic physics
Comparable to Geant3 already in the 1st release (1997)
High energy extensionsHigh energy extensions fundamental for LHC experiments, cosmic ray experiments etc.
Low energy extensionsLow energy extensions fundamental for space and medical applications, neutrino
experiments, antimatter spectroscopy etc.
Alternative models for the same physics processAlternative models for the same physics process
energy lossIt handles
electrons and positrons , X-ray and optical photons muons charged hadrons ions
Maria Grazia Pia, CERN/IT and INFN Genova
OO design
Alternative models, obeying the same abstract interface, are provided for the same physics interaction
Class diagram of electromagnetic physics
Maria Grazia Pia, CERN/IT and INFN Genova
Standard electromagnetic processes
PhotonsPhotons Compton scattering conversion photoelectric effect
Electrons and positronsElectrons and positrons Bremsstrahlung ionisation
continuous energy loss from Bremsstrahlung and ionisation
ray production positron annihilation synchrotron radiation
Charged hadronsCharged hadrons
Shower profile, 1 GeV e- in water
J&H Crannel - Phys. Rev. 184-2 August69
1 keV up to O(100 TeV)1 keV up to O(100 TeV)
Maria Grazia Pia, CERN/IT and INFN Genova
Features of Standard e.m. processes Multiple scatteringMultiple scattering
new model computes mean free path length and
lateral displacement
New energy loss algorithmNew energy loss algorithm optimises the generation of rays near
boundaries
Variety of modelsVariety of models for ionisation and energy loss
including the PhotoAbsorption Interaction model
Differential and Integral approachDifferential and Integral approach for ionisation, Bremsstrahlung, positron
annihilation, energy loss and multiple scattering
Multiple scattering
6.56 MeV proton , 92.6 mm Si
J.Vincour and P.Bem Nucl.Instr.Meth. 148. (1978) 399
Maria Grazia Pia, CERN/IT and INFN Genova
Ionisation energy loss distribution produced by pions, PAI modelPAI model
3 GeV/c in 1.5 cm Ar+CH4
5 GeV/c in 20.5 m Si
PPhoto hoto AAbsorption bsorption IIonisation onisation ModelModel
Ionisation energy loss produced by charged particles in thin layers of absorbers
Maria Grazia Pia, CERN/IT and INFN Genova
Low energy extensions: e-,
Based on EPDL97, EEDL and EADL evaluated data libraries
cross sections sampling of the final state
Photoelectric effect Compton scattering Rayleigh scattering conversion Bremsstrahlung Ionisation Fluorescence
250 eV up to 100 GeV250 eV up to 100 GeV
Photon transmission on 1 m Al
http://www.ge.infn.it/geant4/lowE
Maria Grazia Pia, CERN/IT and INFN Genova
Photon attenuation coefficientPhoton attenuation coefficient
Comparison with NIST data
Standard Standard electromagnetic package
and Low EnergyLow Energy extensions0.01 0.1 1 10
0.01
0.1
1
10
100
1000
Geant4 LowEn NIST
/
(cm
2 /g
) in
iron
Photon Energy (MeV)
Fe
0.01 0.1 1 10-16
-14
-12
-10
-8
-6
-4
-2
0
2
4
6
8
10
12
14
16
Delta = (NIST-G4EMStand) / NIST
Delta = (NIST-G4LowEn) / NIST
Del
ta (
%)
Photon Energy (MeV)
water water
Maria Grazia Pia, CERN/IT and INFN Genova
Low energy extensions: hadrons and ions
E > 2 MeV Bethe-Bloch 1 keV < E < 2 MeV
parameterisations Ziegler 1977, 1985 ICRU 1993 corrections due to chemical formulae
of materials nuclear stopping power
E < 1 keV free electron gas model Barkas effect taken into account down
to 50 keV quantum harmonic oscillator model
Various models, depending on the energy range and chargeVarious models, depending on the energy range and charge
Maria Grazia Pia, CERN/IT and INFN Genova
Muon processes
Validity range
1 keV up to 10 PeV scale1 keV up to 10 PeV scale simulation of ultra-high
energy and cosmic ray physics High energy extensions based
on theoretical models
Bremsstrahlung Ionisation and ray production e+e- Pair production
Maria Grazia Pia, CERN/IT and INFN Genova
Processes for optical photons
Optical photon its wavelength is much greater than the typical atomic spacing
Production of optical photons in HEP detectors is mainly due to Cherenkov effect and scintillation
Processes in Geant4Processes in Geant4 in-flight absorption Rayleigh scattering medium-boundary interactions
(reflection, refraction) Track of a photon entering a light concentrator CTF-Borexino
Maria Grazia Pia, CERN/IT and INFN Genova
Openness to evolutionFrom the Minutes of LCB (LHCC Computing Board) meeting on 21 October, 1997:
Geant4 physics keeps evolvingGeant4 physics keeps evolvingwith attention to UR
facilitated by the OO technologyLower energy extensions, new models for polarisation, new models for material dependence etc.
“It was noted that experiments have requirements for independent, alternative physics models. In Geant4 these models, differently from the concept of packages, allow the user to understand how the results are produced, and hence improve the physics validation. Geant4 is developed with a modular architecture and is the ideal framework where existing components are integrated and new models continue to be developed.”
Maria Grazia Pia, CERN/IT and INFN Genova
User support
User Support is a key feature of Geant4User Support is a key feature of Geant4 Users (experiments, laboratories, institutes) are members of the
collaboration itself User RequirementsUser Requirements are formally collected and regularly updated Extensive documentationdocumentation available from the web (5 manuals)
A Geant4 Training ProgrammeTraining Programme in preparation User Support through a web interface for code-related problem reports User Support through human interface for consultancy, investigation of
anomalous results etc. A distributed modeldistributed model of User Support
a large number of experts performs the support on the domain of their competence
The close relationship with user communities and their feedback is very valuable to Geant4
Maria Grazia Pia, CERN/IT and INFN Genova
Geant4 electromagnetic physics Working Groups M. Maire (LAPP) P. Nieminen (ESA) M.G. Pia (INFN Genova) S. Agostinelli - (IST Genova) P. Andreo (Karolinska Inst.) D. Belkic (Karolinska Inst.) A. Brahme (Karolinska Inst.) A. Carlsson (Karolinska Inst.) G. Cabras (INFN Udine) S. Chauvie (INFN Torino) G. Depaola (Univ. Cordova) R. Cirami (INFN Trieste) E. Daly (ESA) A. De Angelis (INFN Udine) G. Fedel (INFN Trieste) J.M. Fernandez Varea (Univ. Barcelona) S. Garelli (IST Genova) R. Giannitrapani (INFN Udine) V. Grichine (LPI Moscow) I. Gudowska (Karolinska Inst.) P. Gumplinger (TRIUMF)
V. Ivanchenko (Budker Institute ) R. Kokouline (MEPhI, Moscow) E. Lamanna (INFN Cosenza) S. Larsson (Karolinska Inst.) R. Lewensohn (Karolinska Inst.) B.K. Lind (Karolinska Inst.) J. Lof (Karolinska Inst.) F. Longo (INFN Trieste) B. De Lotto (INFN Udine) F. Marchetto (INFN Torino) E. Milotti (INFN Udine) R. Nartallo (ESA) G. Nicco (Univ. Torino) B. Nilsson (Karolinska Inst.) V. Rolando (Univ. Piemonte Orient.) A. Rybin (IHEP Protvino) G. Santin (INFN Trieste) U. Skoglund (Karolinska Inst.) A. Solano (INFN Torino) R. Svensson (Karolinska Inst.) N. Tilly (Karolinska Inst.) L. Urban (KFKI Budapest)
Standard Standard e.m. Physics
Low EnergyLow Energy e.m. Physics
Maria Grazia Pia, CERN/IT and INFN Genova
Conclusions
Geant4 is a simulation Toolkit, providing advanced tools for all the domains of detector simulation
Its areas of application span diverse fields: HEP and nuclear physics, astrophysics and space sciences, medical physics, radiation studies etc.
Geant4 is characterized by a rigorous approach to software engineering
Geant4 electromagnetic physics covers a wide energy range of interactions of electrons and positrons, photons, muons, charged hadrons and ions
An abundant set of electromagnetic physics processes is available, often with a variety of complementary and alternative physics models
Low and high energy extensions have opened new domains of applications
Thanks to the OO technology, Geant4 is open to extension and evolution
Maria Grazia Pia, CERN/IT and INFN Genova
Related presentationsat this conference
V. Grichine Fast Simulation of X-ray Transition Radiation in the Geant4 Toolkit
P. Nieminen Space applications of the Geant4 Toolkit
P. Arce et al. Multiple scattering in Geant4 S. Chauvie Medical applications of the Geant4 Toolkit
http://www.ge.infn.it/geant4/lowE
http://www.ge.infn.it/geant4/dna
http://www.cerninfo.cern.ch/asd/geant4/geant4.html