G EANT 4 and E UDET/ NA2 John Apostolakis, CERN for the G4/SFT team V1.1 Geant4 Highlights VALSIM...

GEANT4 and EUDET/NA2

John Apostolakis, CERN

for the G4/SFT team

V1.1

Geant4 HighlightsVALSIM potential work items

14 December 2005

J Apostolakis for G4/SFT team - EUDET NA2 brainstorming meeting

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Content

• The Context: Geant4, G4 team in PH/SFT• Geant4 Highlights• VALSIM potential work items

Part I: The Context

Geant4 toolkitApplication Areas

G4/SFT team (LCG)

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Geant4 Overview • Powerful structure and kernel

– tracking, stacks, geometry, hits, …• Extensive & transparent physics models

– electromagnetic – hadronic – decay, optical, …

• Interfaces– visualization, GUI, persistency.

• Efficiency enhancing techniques– Framework for fast simulation (shower parameterization)– Variance reduction / event biasing

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Application Areas

• Geant4 in HEP production– BaBar– ATLAS(Q1 2004)– CMS (Q4 2003),– LHCb (Q2 2004)– Harp– …

• Medical applications– Imaging (PET/SPECT)– Dosimetry– Beam optics modeling– Assessing treatment

(hadrontherapy)

• Space – Effects on electronics– Planetary radiation

environment– Radiation in human flights

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G4/SFT team: work areas and people1. Geometry, Field and Transportation

• G Cosmo(coord.), V. Grichine, J. Apostolakis, O. Link (-Dec 2005)2. Software Management, System Testing

• G Folger, G Cosmo, I. McLaren, (also S. Sadilov)3. EM Physics

• V. Ivantchenko (resp./SFT), V. Grichine4. Hadronic Physics / Neutrons

• G. Folger (resp./SFT), M. Kossov, V Ivantchenko, V. Grichine• A. Howard (from Oct 2005, also SI-Physics Validation)

5. Regression testing / validation• A. Ribon (also LCG-AA/SI/Physics Validation)

6. Coordination / Release• J. Apostolakis, G. Cosmo

Part II: Physics

Using the Physics via ‘Physics lists’&

Underlying physics modeling

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Different types of hadronic shower models

• Parameterization-driven models– Started from GHEISHA, revised/improved

• Theory driven models– Pre-compound– Cascades and CHIPS– String models

• Data driven models– Neutrons E<20 MeV– Photo-evaporation of nuclei

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Models in hadronic framework

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Theory driven models (1/2)• Models derived from approximate/phenomenological

models – QCD, strings, chiral perturbation theory, statistical collective

• Only thin-target data used for verification • Final states determined by sampling theoretical

distributions• Philosophy implies the usage physics lists, providing

wanted collection of models, such as:– Parton string models at high energies, – intra-nuclear transport models at intermediate energies, and– statistical break-up models for de-excitation

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Theory driven models (2/2)• Parton string:

– Projectiles with E > 5 GeV – Wounded nucleus is de-excited by ‘attached’ model (pre-compound or Chips)

• Cascade energy-range models– Bertini cascade (next slides)– Binary cascade– Chiral invariant phase space, CHIPS:

• Quark-level event generator for the fragmentation of hadronic systems into hadrons

– All energies • Interactions between hadrons are treated as purely kinematic effects of

quark exchange• Decay of excited hadronic systems is treated as the fusion of two quark-

partons within the system• Includes non-relativistic phase space of nucleons to explain evaporation

• Nuclear de-excitation and breakup

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Bertini intra-nuclear cascade (1/2)

• Collection of theory driven models with parametrisation features:

• Intermediate energies ~100 keV – 10MeV • Models included:

– Bertini INC model with exitons– Pre-equilibrium model– Nucleus explosion model– Fission model– Evaporation model

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Bertini intra-nuclear cascade (2/2)• For A>4 a nuclei model is

composed of three concentric spheres

• Impulse distribution in each region follows Fermi distribution with zero temperature

• Particle treated p,n, pions, photon evaporation and nuclear isotope remnats

• Latest addition include incident kaons up to an energy of 15 GeV:– Final states, will be included

for K+, K-, K0, K0bar, lambda, sigma+, sigma0, sigma-, xi0 and xi-

Schematic presentation of the intra-nuclear cascade. A hadron with 400 MeV energy is forming an INC history. Crosses present the Pauli exclusion principle in action.

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Hadronic model inventory

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Geant4 LEP model (derived from Geant 3.21 and improved)

pion production from 730 MeV proton on Carbon.

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Bertini cascade model pion production from 730 MeV proton on Carbon.

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Tailored Physics ‘lists’• Created and distribute “educated guess” physics lists

– correspond to major use cases of Geant4 involving hadronic physics,– to use directly, and as a starting point for users to modify,

• facilitate the specialization of those parts of hadronic physics lists that vary.– First released in September 2002

• Revised with experience of comparisons with data– This provide ‘tested’ options, with known performance – Last major revision for physics models of Geant4 6.2 (June 2004)

• Distribution– Most up-to-date from the G4 hadronic physics web pages

http://cern.ch/geant4/physics_lists– Included in Geant4 releases

• Starting with Geant4 6.0 (Dec 2003), ported versions in major releases• Current physics lists version is included in minor releases, patches.

http://cern.ch/geant4/physics_lists

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Hadronic physics: Hadronic physics: models, processes and ‘lists’ models, processes and ‘lists’

Illustrative example of Illustrative example of assemblingassembling models into an inelastic process for set models into an inelastic process for set of particlesof particles– Uses levels 1 & 2 of frameworkUses levels 1 & 2 of framework

Cascade

QGSM

ParameterizedEn

ergy

Element

particle

Pre-compoundmodel

Five level implementation frameworkVariety of models and cross-sections

for each energy regime, particle type, materialalternatives with different strengths and CPU requirements.

Components can be assembled in an optimized way for each use case.

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Use cases of Physics Lists• HEP calorimetry. • HEP trackers. • 'Average' HEP collider detector • Low energy dosimetric

applicationswith neutrons

• low energy nucleon penetration shielding

• linear collider neutron fluxes• high energy penetration

shielding• medical and life-saving neutron

applications

• low energy dosimetric applications

• high energy production targetse.g. 400GeV protons on C or Be

• medium energy production targetse.g. 15-50 GeV p on light targets

• LHC neutron fluxes • Air shower applications • low background experiments

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Physics lists / ‘engines’ for calorimetry

• LHEP is the fastest for CPU– uses the LEP and HEP

parameterized models for inelastic scattering.

• QGSP – uses theory-driven modeling for

reactions of s, Ks, and nucleons• for primaries with E starting at ~ 12

GeV, dominant above 30 GeVIt employs – Quark Gluon String Model

• for the 'punch-through' interactions of the projectile

– A Pre-equilibrium decay model • with an extensive evaporation

phase that model the nucleus 'after the punch‘

– For other energies uses LHEP models

• QGSC, is similar to QGSP but uses CHIPS for fragmentation

– The CHiral Invariant Phase-Space decay (CHIPS)

– QGS now starts at 9 GeV

• FTFP starts with QGSP and replaces the string

– with a diffractive string excitation • similar to that in FRITJOF, and

the Lund fragmentation functions.

• Note: A (g – nuclear) interactions recently added to all options.

– Previously available as _GN variants, eg QGSP_GN

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Relevant comparisons for HEP: A partial list• ATLAS test beams

– FCAL , e, – HEC , e-, – EM Barrel– TileCal– TRT– Muon chambers (extra

hits)– …

• BaBar data– Drift Chamber

• ALICE– 100s MeV proton microscopic– TIARA neutron benchm.

• CMS – HCAL test beam

• BTeV– ECAL test beam

Very hard to give just a few highlights …

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Hadronic Physics: theoretical models

• Evaporation/pre-compound• Bertini Cascade / INUCL

– extended to Kaons, up to 5-10 GeV, verified isotope production

• Binary cascade– Extended to ion reactions, pion projectiles

• CHIPS ‘Chiral Invariant Phase-space decay’ -A, e-A, absorption, p-bar annihilation at rest

• QGSM string model– improved meson splitting

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Latest • Geant4 8.0 will include

– Refinements and new features in the kernel– New models, improvements & refinements in EM

• Revision of multiple scattering model (angle/lateral) & process (step limits)

• Using & extending ‘model-based’ implementation of EM standard– Improvements & fixes models in hadronics

• Revisions to ‘LElastic’, and refined precision ‘coherent’ process• Neutrino – nucleus using CHIPS

– Revised ‘Physics-lists’• Revised to use EM builders, non-static particles• Utilize revised physics processes (in most PLs).

http://cern.ch/geant4

Part III: Validation / Testing

Regression ‘suite’

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Statistical testing 2004/5• Establishment of ‘statistical testing’ suite

– Automated comparison of physics quantities– Simple setups for ‘regression testing’

• Simplified, typical LHC hadronic calorimeters (only E deposit, no digitisation)• Additional testing suites

– Against ‘standard’ data• T. Koi (SLAC) : hadron / ion comparison• INFN : EM interactions, per process X-sections vs. NIST

• Extensions of suite under consideration– Further setups (EM calor.), quantities – Reusing donated ‘test-beam’ comparisons

• Full applications from ATLAS, CMS.– For details see presentations of A. Ribon (Tech Forum, AA meeting)

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Challenges / Ongoing

• Regression suite is identifying changes– Identified problems (crashes) – fixed– Must establish more ‘links’ to verification/sub-system

tests– Limits to automated testing when revising models

• Not to forget user/experiment acceptance tests

• Performance improvement– Large productions / always a goal

• Expanding use of ‘best-practice’– Eg new methods to identify ‘hard’ problems

Part IV: Potential Work Issues

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Verification of physical processes

Review of physical processes for key detector materials (Verification)• Materials: Si, W, gases (Ar, CO2, CH4, CF2), ...

• Verification for key processes in relevant materials (using thin target data)

• Comparison/validation of detailed interaction products d2 / dE d in particular for hadronic interactions

• Potential additional 'details' – catastrophic muon energy loss– - e+ to hadrons (due to annihilation)– synchrotron radiation in medium (LPM-like effects)

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Benchmarking of neutron modeling

Key aspects of use cases: neutrons as background, activation, hazard/shielding.

• Identified/candidate benchmarks – TIARA (shielding) (*)– Los Alamos 'thin target' (neutron generation) (*)– Particular CERF setups (shielding, activation, ...)– TARC (spallation, elastic interactions, capture),– new data (eg latest data with 14 MeV n)– Note: (*) comparisons exist, typically >= 2 years old

• Review / update data for data-driven neutron modelling (E<20 MeV)• Other aspects

– Radiation effects in silicon: joint investigation with space community – Radiation and effects on endcap detectors

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3.) Hadronic shower development

• Neutron, EM, charged fractions– identify and utilise available benchmarks for EM fraction, neutrons– comparisons with test-beam results of existing/smaller-scale segmented-

calorimeters• hadronic shower shape: comparisons with data and regression testing

– extend comparisons with data– extend calorimeter regression suite with setups relevant to proposed

detectors • Effect of hadronic interactions in ECAL

– Identify aspects/elements affecting simulation's assessment of impact of ECal thickness, material

• Comparisons of modeling of jet showers and EM showers– effect of choice of physics models– Assessing strengths/weaknesses of available physics lists for shower

simulation in segmented calorimeter

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4.) Other/Technical aspects• Coupled propagation/navigation in 'parallel'

geometries in presence of fields• Biasing

– revision of importance biasing (for parallel navigation)• Scoring

– Re-factoring/improving existing and creating new 'standard' tallies

• CPU performance – Unique aspects for highly granular detectors (EM

showers, field, neutrons?)– Propagation in strong magnetic fields

THE END

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Geant4 6.0 - general picture1. New capabilities in Geant4 6.0 for HEP

Latest Physics lists distributed ‘inside’ EM-std new ‘model’ implementation by default

2. Highlights of improvements to existing physics modeling & models; in physics process implementations; in functionality

The high level of user feedback is reflected in developments, fixes & improvements

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Hadronic Physics Lists• The latest physics lists included since 6.0

– 8.0 ported from lists in 7.1 (June 2005)• Porting (new particles), revised modeling (Mult. Scat., ..)• Regression testing undertaken Nov/Dec on LCG/EGEE Grid

– New/revised versions of physics-lists to be released• Revisions to be quickly included in Geant4 patches, releases• When required also via physics lists Web site

• Physics lists and builders are/can-be used:– As is, compiled in a ‘deployment’ directory– Altered (or additional/customized version) by

user/experiment, in own installation

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EM Physics Processes• New “model-based” EM

standard physics processes are now the default– for maintaining and refining– keeping user code unchanged

• Old (frozen) implementation is still available

– Issues encountered in transition

• Fixed in 6.0 patch 1 and 6.1• Fix for repeatability issue

– Multiple scattering does not use tables (due to ions)

• Refinements– Tail of multiple scat. angular

distribution

• New in Low Energy EM– New models (2BN, 2BS) for

Bremstrahlung (Lisbon & INFN)

– New processes for electrons & positrons (a-la Penelope)

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EM Physics Processes & more …• Multiple scattering

• Tuning for tail of angular distribution• Improvement for muons of E>1 PeV

• Ionisation• Updated energy intervals, fluctuation models …• Multiple scattering does not use table

– Needed to ensure repeatability• Added PAI (Photon-Absorption-Ionisation) model

• EM low energy physics• New models (2BN, 2BS) for Bremstrahlung• New processes for electrons & positrons (a-la Penelope)

• Optical processes• New process for wavelength shifting• Adoption of G4SurfaceProperty class for materials

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Hadronic Models: new• Evaporation models

– Ablation: new model for use with abrasion code– GEM-like model implementation– HETC emission probabilities for Weisskopf-Ewing evaporation model

• Ion Reactions– Wilson’s Abrasion for induced ion reactions. – EM dissociation for ion-ion collisions

• High energy elastic scattering: new Coherent_elastic model– requires a new data set for elastic scattering data (provided)

• Diverse– new - nuclear absorption code– Improved fast radioactive decay code– GNASH2 transition probabilities now available from exciton

precompound model

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Hadronics: Cross Sections & Scattering

• Cross sections: – Newest pion scattering data ‘Barashenkov’, remove

discontinuities – Fix in high energy p-H cross-sections (G3 legacy bug)– Ion-ion cross-sections

• Tripathi's systematics for ion-ion cross-sections for light ions• Parameterizations from Shiver, Kox and Shen

• Scattering term – extended for nucleon induced reactions to 8 GeV – included s-wave absorption– pion induced reactions (up to 1.5 GeV)

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Models: Cascade energy range

• Parameterized process (1997)• Chiral Invariant Phase Space decay,“CHIPS”

– For -Nucleus, capture, string-’backend’• First release Dec 2001 in Geant4 4.0• Refinements and extension in 2002

• Bertini cascade (Dec 2002, Geant4 5.0)– Re-engineered from HETC by HIP

• See the presentation of A Heikinen• Binary cascade model (Frankfurt, CERN)

– First release for nucleon induced interactions (in G4 5.0) • Extensive verification suite

– See CHEP 03 presentation by D. Wright, V. Ivantchenko, ..• For further details,

– see the CHEP 03 presentation by J.P. Wellisch

M Kosov, P Degtyarenko,

JP Wellisch

A HeikinenN Stepanov

JPWG Folger

JPW

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EM regression testing

• TestEm – Added check for automating regression tests

• First observable: on average energy deposit • activated by UI command (in 3 of 9 tests) • Improving regression/‘acceptance’ testing

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User Interaction• Geant4 Technical Forum (http://cern.ch/geant4/technical_forum)

– Quarterly meeting• open to interested people

– Users & developer dialog• Identify & prioritize issues

• LCG ‘Physics Validation’ meeting– Comparisons with test beam data– Several new physics developments presented

• We continue to emphasize identifying problems– To enable better use in large production

• To solve issues seen by diverse users• Growing feedback

– Requests for refinements– Problems reported (many identifying the underlying issue)

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Kernel: Propagation in EM Field• Transportation can keep some ‘loopers’

– From 7.0, tracks with E > Eimportant go on for n ‘long’ steps

• Default Eimportant =250 MeV) • Ability to specialize integration accuracy

min, max now for each Field-Manager• Choice of Field-Manager by track

e.g. more precise for muon or for tracks E>5 GeV• Ability to use variant Chord-Finder (5.2)

Can use safety, radius of curvature, other infoFor performance improvement

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Kernel: summaryDevelopment• Modular Run Manager• Better HEPMC input• Abstract Navigator• New Biasing

– Biasing:“weight-window” technique

Refinements• General Particle Source

– Design iteration• Integration of motion in field

– Enabled tuning of accuracy parameters for particle type, Energy, …

ImprovementsNavigator:• New ‘check mode’ • better verbosity

Fixes• Corrected ‘safety’ in solids

– Addressed propagation & photon problems

• Reported by LHCb

• Fixes for case of missed intersections in field

– purging magnet example• Fixes for a 'point outside' problem

seen in solids– problem in displacement in field

View of Atlas toroidCourtesy of Atlas

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Debugging geometries• It is easy to create overlapping volumes

– During tracking Geant4 does not check for malformed geometries

• The problem of detecting ‘significant’ overlaps is now addressed by– DAVID intersects graphics volumes

• Created by S. Tanaka, released ca 1997 – Commands to run verification tests

• Created by DC Williams; released in 4.0• New capabilities added in 5.2 (June 2003)

– New example with full tracking / navigation• Created by M Liendl (CMS); released in 5.0

Thanks to S. Tanaka

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Kernel Changes for 7.0Kernel Changes for 7.0

Several changes in kernel are planned for the 7.0 release. In order of the effects:• New scheme of storing/retrieving physics tables

– Enables user to read a portion & generate the rest• New particle “unknown” and new process “unknown decay”

– For particles whose physics is not simulated, we now create– Enables full decay chains to be treated uniformly

• New dedicated class for user step limitation– Separating step length limitation and track killing

• Possibility of altering detector sensitivity with the parameterized volume– Categories affected: Tracking, Track, Processes/transportation

• New design of particles, replacing static-singletons– Under discussion: may affect code that creates physics processes.

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‘Platform’ changes• OS / compiler ‘movement’

– Newly supported (June 2004)• gcc 3.2.3 on Linux (RH 7.3 &

SLC 3)• Visual C++ .net 7.1 on

Windows XP– Emerging platforms

(‘verified’)• MacOs 10.3 with gcc 3.3• icc 8.0 (IA-32 & IA-64)

– Checking for porting• Latest gcc: 3.3.3 and now 3.4

– Dropped end-2003: egcs– To drop end-2004: gcc 2.95.2 &

Vis C++ 6

• Enabled shared-library mechanism for Windows – With 6.2, end-June 2004– Request of LHCb

Goal– keep up with needs user

communities– Do integration testing on at

least 3 platforms• Not more than 5, if

possible

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Upcoming Releases• Developments available

– In monthly development tags– In open releases each quarter

• Except if there is a scheduled or consolidating minor release.• Upcoming releases

– ‘Scheduled’ major release Geant4 7.0 in mid-December• New developments• Improvements and other refinements• Any fixes, further performance improvements.

– 2004 work items & planned release contents• At URL http://cern.ch/geant4/source/planned_features.html• Started from requirements and requests of users/experiments

http://cern.ch/geant4/source/planned_features.html

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Established new releases & new features

• Established releases– End of June (minor release)– End of December (major release)

• Planning the new activities for 2004– taking into consideration requirements of all users

including those from LHC experiments / LCG– Users’ Technical Forum at CERN

• February 5th, 15:00-17:30• Requirements collection and first-level prioritization

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• Geant4 is evolving– Feedback from HEP experiments, and users in

medical, space domains.– Regular Users’ Technical Forum meetings to

collect/sort requirements and prioritise

Part II: The ‘Kernel’

New developments & improvementsin Geometry, Tracking,Run & Event handling

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Kernel: Geometry• Describing model geometries

– Solids• Navigation• Field propagation

• Active areas– Additional checking of navigation & model geometry– Abstraction of G4Navigator– Solids:

• Revision of surface normals (booleans)• New shapes (twisted solids, ellipsoidal solids)

– New volume types • Refinement/extensions to parameterised volumes

– Optimisation of field propagation

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Variance reduction • Importance biasing:

– Splitting/Russian roulette (G4 4.1, June 2002).– Importance values for a volume

• In the ‘mass’ geometry or in a dedicated ‘parallel’ geometry.

– Used for shielding (speedup demonstrated)– Limited in case of fields to ‘mass’ geometry

• To be addressed via ‘coupled’ parallel navigation

• Other ‘general’ methods (eg forced interaction) – Some existing, others in development

M Dressel

N.Kanaya

G EANT 4 and E UDET/ NA2 John Apostolakis, CERN for the G4/SFT team V1.1 Geant4 Highlights VALSIM...

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