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## Sunanda Banerjee ( Saha Inst. Nucl . Phys., Kolkata, India)

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**IEEE Nuclear Science Symposium and Medical Imaging**ConferenceShort CourseThe Geant4 Simulation Toolkit Sunanda Banerjee (Saha Inst. Nucl. Phys., Kolkata, India) Min Cheol Han (Hanyang Univ., Seoul, Korea) Steffen Hauf(XFEL, Hamburg, Germany) Maria Grazia Pia (INFN Genova, Italy) MariaGrazia.Pia@ge.infn.it Seoul, 27 October 2013 http://www.ge.infn.it/geant4/events/nss2013/geant4course.html This course encompasses training material developed by several Geant4 members: thanks to all of them!**Outline**• Overview of hadronic physics • processes, cross sections, models, hadronic framework and organization • Elastic scattering • Precompound models • Cascade models • Bertini-style, binary, INCL/ABLA • Neutron physics • HP models, LEND models • Ion-ion physics • Wilson abrasion/ablation, binary light ion cascade, INCL++, QMD • Radioactive decay • Gamma- and lepto-nuclear models • QCD string models • Quark-gluon string (QGS) model, Fritiof (FTF) model • Other Models • Capture, Fission Geant4 Hadronics**Hadronic Processes, Models and Cross Sections**• In Geant4 physics is assigned to a particle throughprocesses • Each process may be implemented • directly, as part of the process, or • in terms of a model class • Geant4 often provides several models for a given process • user must choose • can, and sometimes must, have more than one per process • A process must also havecrosssectionsassigned • here too, there are options Geant4 Hadronics**particle**process 1 at rest process 2 in-flight process 2 process n model 1 model 2 .. .. model n c.s. set 1 c.s. set 2 … … c.s. set n Energy range manager Cross section data store Geant4 Hadronics**Cross Sections**• Default cross section sets are provided for each type of hadronic process • fission, capture, elastic, inelastic • can be overridden or completely replaced • Different types of cross section sets • some contain only a few numbers to parameterize the cross section • some represent large databases • some are purely theoretical (equation-driven) Geant4 Hadronics**Alternative Cross Sections**• Low energy neutrons • G4NDL available as Geant4 distribution files • Livermore database (LEND) also available • available with or without thermal cross sections • Medium energy neutron and proton reaction cross sections • 14 MeV < E < 20 GeV • Ion-nucleus reaction cross sections (several alternatives exist) • These are empirical and parameterized cross section formulae with some theoretical insight • good for E/A < 10 GeV • Pion reaction cross sections Geant4 Hadronics**Cross Section Management**GetCrossSection() sees last set loaded within energy range Set 4 Load sequence Set 3 Set 2 Set 1 Default cross section set Energy Geant4 Hadronics**Data-driven Hadronic Models**• Characterized by lots of data • cross sections • angular distributions • multiplicities, etc. • To get interaction length and final state, models depend on interpolation of data • cross sections, Legendre coefficients • Examples • neutrons (E < 20 MeV) • coherent elastic scattering (pp, np, nn) • radioactive decay Geant4 Hadronics**Theory-driven Hadronic Models**• Dominated by theoretical arguments (QCD, Glauber theory, exciton theory…) • Final states (number and type of particles and their energy and angular distributions) determined by sampling theoretically calculated distributions • This type of model is preferred, as it is the most predictive • Examples • quark-gluon string (projectiles with E > 20 GeV) • intra-nuclear cascade (intermediate energies) • nuclear de-excitation and break-up Geant4 Hadronics**Parametrized Hadronic Models**• Depend mostly on fits to data with some theoretical guidance • Two such models available: • Low Energy Parameterized (LEP) for E < 20 GeV • High Energy Parameterized (HEP) for E > 20 GeV • each type refers to a collection of models (one for each hadron type) • Both LEP and HEP are re-engineered versions of the Fortran Gheisha code used in Geant3 • Code is fast and applies to all particle types, but is not particularly detailed • will be phased out by Geant4 10.0 Geant4 Hadronics**Partial Hadronic Model Inventory**Atrestabsorption, , , K, anti-p Photo-nuclear, electro-nuclear Radioactivedecay Electro-nuclear dissociation QMD (ion-ion) Highprecisionneutron WilsonAbrasion Pre-compound Evaporation Fermibreakup Multifragment PhotonEvap QuarkGluonstring Binarycascade Fritiof string Bertini-stylecascade 1 MeV 10 MeV 100 MeV 1 GeV 10 GeV 100 GeV 1TeV Geant4 Hadronics**Model Management**Model returned by GetHadronicInteraction() 1 1 + 3 3 Error 2 Error 2 Model 3 Model 4 Model 1 Model 2 Energy Geant4 Hadronics**Hadronic Model Organization**process at rest discrete (in-flight) models theory framework spallation framework high energy parton-string propagate precompound cascade string fragmentation evaporation Geant4 Hadronics**Hadronic Interactions from TeV to meV**TeVhadron ~GeV to ~100 MeV dE/dx ~ A1/3 GeV p, n, d, t, and n ~100 MeV to ~10 MeV ~10 MeV to thermal Geant4 Hadronics**Hadron Elastic Scattering**• G4WHadronElasticProcess: general elastic scattering • valid for all energies • valid for p, n, π , K, hyperons, anti-nucleons, anti-hyperons • based in part on old Gheisha code, but with relativistic corrections • Coherent elastic • G4LEpp for (p,p), (n,n) : taken from SAID phase shift analysis, good up to 1.2 GeV • G4LEnp for (n,p) : same as above • G4HadronElastic for general hadron-nucleus scattering • Neutron elastic • high precision (HP) model uses data from ENDF (E < 20 MeV) Geant4 Hadronics**Elastic Scattering Validation(G4HadronElastic)**Geant4 Hadronics**Precompound Models**• G4PrecompoundModel is used for nucleon-nucleus interactions at low energy and as a nuclear de-excitation model within higher-energy codes • valid for incident p, n from 0 to 170 MeV • takes a nucleus from a highly excited set of particle-hole states down to equilibrium energy by emitting p, n, d, t, 3He and α • once equilibrium is reached, four other models are called to take care of nuclear evaporation and break-up • these 4 models not currently callable by users • The parameterized models and two cascade models have their own version of nuclear de-excitation models embedded in them Geant4 Hadronics**Precompound Models**• Invocation of Precompound model: G4ExcitationHandler* handler = new G4ExcitationHandler; G4PrecompoundModel* preco = new G4PrecompoundModel(handler); // Create de-excitation models and assign them to precompound model G4NeutronInelasticProcess* nproc = new G4NeutronInelasticProcess; nproc->RegisterMe(preco); neutronManager->AddDiscreteProcess(nproc); // Register model to process, process to particle • Here the model is invoked in isolation, but usually it is used in combination with high energy or cascade models • a standard interface exists for this Geant4 Hadronics**Bertini-style Cascade Model**• A classical (non-quantum mechanical) cascade • average solution of a particle traveling through a medium (Boltzmann equation) • no scattering matrix calculated • can be traced back to some of the earliest codes (1960s) • Core code: • elementary particle collisions with individual protons and neutrons: free space cross sections used to generate secondaries • cascade in nuclear medium • pre-equilibrium and equilibrium decay of residual nucleus • target nucleus built of three concentric shells Geant4 Hadronics**Using the Bertini Cascade**• In Geant4 the Bertini cascade is used for p, n, +, -, K+, K-, K0L , K0S, , 0 , + , - , 0 , X-, W- • valid for incident energies of 0 – 10 GeV • can also be used for gammas • Invocation sequence • G4CascadeInterface* bert = new G4CascadeInterface; • G4ProtonInelasticProcess* pproc = new G4ProtonInelasticProcess; • pproc->RegisterMe(bert); • protonManager->AddDiscreteProcess(pproc); • // same sequence for all other hadrons and gamma Geant4 Hadronics**Validation of Bertini Cascade**Geant4 Hadronics**Binary Cascade Model**• Modeling sequence similar to Bertini, except • it’s a time-dependent model • hadron-nucleon collisions handled by forming resonances which then decay according to their quantum numbers • particles follow curved trajectories in smooth nuclear potential • Binary cascade is currently used for incident p, n and π • valid for incident p, n from 0 to 10 GeV • valid for incident π+, π– from 0 to 1.3 GeV • A variant of the model, G4BinaryLightIonReaction, is valid for incident ions up to A = 12 (or higher if target has A < 12) Geant4 Hadronics**Using the Binary Cascade**• Invocation sequence: • G4BinaryCascade* binary = new G4BinaryCascade(); • G4PionPlusInelasticProcess* piproc = • new G4PionPlusInelasticProcess(); • piproc->RegisterMe(binary); • piplus_Manager->AddDiscreteProcess(piproc); • Invoking BinaryLightIonReaction • G4BinaryLightIonReaction* ionBinary = • new G4BinaryLightIonReaction(); • G4IonInelasticProcess* ionProc = new G4IonInelasticProcess(); • ionProc->RegisterMe(ionBinary); • genericIonManager->AddDiscreteProcess(ionProc); Geant4 Hadronics**Validation of Binary Cascade256 MeV protons**Geant4 Hadronics**INCL++ Cascade Model**• Model elements: • time-dependent model • smooth Woods-Saxon or harmonic oscillator potential • particles travel in straight lines through potential • delta resonance formation and decay (like Binary cascade) • Valid for incident p, n and π, d, t, 3He, α from 150 MeV to 3 GeV • also works for projectiles up to A = 12 • targets must be 11 < A < 239 • ablation model (ABLA) can be used to de-excite nucleus • Used successfully in spallation studies • also expected to be good in medical applications Geant4 Hadronics**Validation of INCL ModelGreen: INCL4.3 Red: INCL4.2 Blue:**Binary cascade Geant4 Hadronics**Low Energy Neutron Physics**• Below 20 MeV incident energy, Geant4 provides several models for treating neutron interactions in detail • The high precision models (NeutronHP) are data-driven and depend on a large database of cross sections, etc. • the G4NDL database is available for download from the Geant4 web site • elastic, inelastic, capture and fission models all use this isotope-dependent data • There are also models to handle thermal scattering from chemically bound atoms Geant4 Hadronics**Geant4 Neutron Data Library (G4NDL)**• Contains the data files for the high precision neutron models • includes both cross sections and final states • From Geant4 9.5 onward, G4NDL is based solely on the ENDF/B-VII database • G4NDL data is now taken only from ENDF/B-VII, but still has G4NDL format • use G4NDL 4.0 or later • Prior to G4 9.5 G4NDL selected data from 9 different databases, each with its own format • Brond-2.1, CENDL2.2, EFF-3, ENDF/B-VI, FENDL/E2.0, JEF2.2, JENDL-FF, JENDL-3 and MENDL-2 • G4NDL also had its own (undocumented) format Geant4 Hadronics**G4NeutronHPElastic**• Handles elastic scattering of neutrons by sampling differential cross section data • interpolates between points in the cross section tables as a function of energy • also interpolates between Legendre polynomial coefficients to get the angular distribution as a function of energy • scattered neutron and recoil nucleus generated as final state • Note that because look-up tables are based on binned data, there will always be a small energy non-conservation • true for inelastic, capture and fission processes as well Geant4 Hadronics**G4NeutronHPInelastic**• Currently supports 34 inelastic final states + n gamma (discrete and continuum) • n (A,Z) → (A-1, Z-1) n p • n (A,Z) → (A-3, Z) n n n n • n (A,Z) → (A-4, Z-2) d t • ……. • Secondary distribution probabilities • isotropic emission • discrete two-body kinematics • N-body phase space • continuum energy-angle distributions (in lab and CM) Geant4 Hadronics**Neutron Inelastic: 154Gd (n,2n)Comparison to Data**Geant4 Hadronics**G4NeutronHPCapture**• Neutron capture on a nucleus produces photons described by either • the number of photons (multiplicity), or • photon production cross sections • Photon spectra are either • discrete emission, using either cross sections or multiplicities from data libraries, or • continuous, with the spectrum calculated according to tabulated parameters • f(E->Eg) = Si pi(E) gi(E->Eg) where pi and gi come from the libraries Geant4 Hadronics**High Precision NeutronsComparing Geant4 and MCNPX**Geant4 Hadronics**G4NeutronHPFission**• Currently only uranium fission data are available in Geant4 • First chance, second chance, third chance and fourth chance fission taken into account • Resulting neutron energy distributions are implemented in different ways • as a function of incoming and outgoing neutron energy • as a Maxwell spectrum • evaporation spectrum • energy-dependent Watt spectrum • Madland-Nix spectrum Geant4 Hadronics**Including HP Neutrons in the Physics List**• Elastic scattering • G4HadronElasticProcess* theNEP = new G4HadronElasticProcess; • // the cross sections • G4NeutronHPElasticData* theNEData = new G4NeutronHPElasticData; • theNEP->AddDataSet(theNEData); • // the model • G4NeutronHPElastic* theNEM = new G4NeutronHPElastic; • theNEP->RegisterMe(theNEM); • neutManager->AddDiscreteProcess(theNEP); Geant4 Hadronics**G4NeutronHPorLE Models**• The high precision neutron models do not cover all elements/isotopes • often no data: latest G4NDL has 395 isotopes, but there are thousands • data may exist but not yet be evaluated • A Geant4 application must have a model under all circumstances, otherwise a fatal error occurs • G4NeutronHPorLE models were developed to solve this problem • HPorLE models call the HP models if data exists • if no data, the Low Energy Parameterized (GHEISHA-style) model is called • elastic, inelastic, capture and fission provided Geant4 Hadronics**Thermal Neutron Scattering from Chemically Bound Atoms**• At thermal energies, atomic motion, vibration, rotation of bound atoms affect neutron scattering cross sections and the angular distribution of secondary neutrons • The energy loss (or gain) of such scattered neutrons may be different from those from interactions with unbound atoms • Original HP models included only individual Maxwellian motion of target nucleus (free gas model) • New behavior handled by model and cross section classes • G4HPThermalScatteringData, and • G4HPThermalScattering Geant4 Hadronics**LEND – the new Livermore Neutron Models**• An alternative to the HP models • better code design • faster • Livermore database not yet as extensive G4NDL • Corresponding model for each model in HP • elastic, inelastic, capture, fission • Invocation in physics list: • use model names G4LENDElastic, G4LENDInelastic, G4LENDCapture, G4LENDFission, and cross sections G4LENDElasticCrossSection, G4LENDInelasticCrossSection, G4LENDCaptureCrossSection, G4LENDFissionCrossSection • Database to use: go toftp://gdo-nuclear.ucllnl.org/pub/and select G4LEND, then ENDF-B-VII.0.targ.gz Geant4 Hadronics**Ion-Ion Inelastic Scattering**• Up to now we’ve considered only hadron-nucleus interactions, but Geant4 has five different nucleus-nucleus collision models • G4BinaryLightIon • G4WilsonAbrasion/G4WilsonAblation • G4EMDissociationModel • G4QMD • G4Incl • Also provided are several ion-ion cross section data sets • Currently no ion-ion elastic scattering models provided Geant4 Hadronics**G4BinaryLightIonReaction**• This model is an extension of the G4BinaryCascade model (to be discussed later) • The hadron-nuclear interaction part is identical, but the nucleus-nucleus part involves: • preparation of two 3D nuclei with Woods-Saxon or harmonic oscillator potentials • lighter nucleus is always assumed to be the projectile • nucleons in the projectile are entered with their positions and momenta into the initial collision state • nucleons are interacted one-by-one with the target nucleus, using the original Binary cascade model Geant4 Hadronics**G4WilsonAbrasion and G4WilsonAblation**• A simplified macroscopic model of nucleus-nucleus collisions • based largely on geometric arguments • faster than Binary cascade or QMD models, but less detailed • The two models are used together • G4WilsonAbrasion handles the initial collision in which a chunk of the target nucleus is gouged out by the projectile nucleus • G4WilsonAblation handles the de-excitation of the resulting fragments • Based on the NUCFRG2 model (NASA TP 3533) • Can be used up to 10 GeV/n Geant4 Hadronics**Wilson Abrasion/Ablation**Geant4 Hadronics**G4EMDissociation Model**• Electromagnetic dissociation is the liberation of nucleons or nuclear fragments as a result of strong EM fields • as when two high-Z nuclei approach • exchange of virtual photons instead of nuclear force • Useful for relativistic nucleus-nucleus collisions where the Z of the nucleus is large • Model and cross sections are an implementation of the NUCFRG2 model (NASA TP 3533) • Can be used up to 100 TeV Geant4 Hadronics**INCL Nucleus-Nucleus**• INCL hadron-nucleus model used to interact projectile nucleons with target • True potential is not used for projectile nucleus, but binding energy is taken into account • True potential is used for target • Projectile nucleons can pass through to form fragment or interact with nucleus Geant4 Hadronics**G4QMD Model**• BinaryLightIonReaction has some limitations • neglects participant-participant scattering • uses simple time-independent nuclear potential • imposes small A limitation for target or projectile • Binary cascade base model can only go to 5-10 GeV • Solution is QMD (quantum molecular dynamics) model • an extension of the classical molecular dynamics model • treats each nucleon as a gaussian wave packet • propagation with scattering which takes Pauli principal into account • can be used for high energy, high Z collisions Geant4 Hadronics**QMD Validation**Geant4 Hadronics**Including QMD in the Physics List**• G4HadronInelasticProcess* ionInel = • new G4HadronInelasticProcess(“ionInelastic”, G4GenericIon::G4GenericIon()); • // the cross sections • G4TripathiCrossSection* tripCS = new G4TripathiCrossSection; • G4IonsShenCrossSection* shenCS = new G4IonsShenCrossSection; • ionInel->AddDataSet(shenCS); • ionInel->AddDataSet(tripCS); • // assign model to process • G4QMDReaction* theQMD = new G4QMDReaction; • ionInel->RegisterMe(theQMD); • G4ProcessManager* pman = G4GenericIon::G4GenericIon()-> • GetProcessManager(); • pman->AddDiscreteProcess(ionInel); Geant4 Hadronics**Radioactive Decay**Geant4 Hadronics • Process to simulate radioactive decay of nuclei • in flight • at rest • a, b+, b– decay, electron capture (EC) implemented • Empirical and data-driven • data files taken from Evaluated Nuclear Structure Data Files (ENSDF) • half lives, nuclear level structure for parent and daughter nuclides, decay branching ratios, energy of decay process • If daughter of nuclear decay is an isomer, prompt de-excitation is done by using G4PhotonEvaporation • Analog (non-biased) sampling is the default • Biased sampling also implemented**Using Radioactive Decay**Geant4 Hadronics • Can be accessed with messengers (biasing options, etc.) • To put in your physics list: G4RadioactiveDecay* theDecay = new G4RadioactiveDecay; G4ProcessManager* pmanager = G4ParticleTable::GetParticleTable()-> FindParticle(“GenericIon”)->GetProcessManager(); pmanager->AddProcess(theDecay); pmanager->SetProcessOrdering(theDecay, idxPostStep); pmanager->SetProcessOrdering(theDecay, idxAtRest);