Hadronic Physics Reference Physics Lists Geant 4 Tutorial

Hadronic Physics & Reference Physics Lists Geant 4 Tutorial Annecy, November 2008 Gunter Folger Geant 4 course, Annecy 2008 Gunter Folger / CERN

Outline • Overview of hadronic physics n n processes, cross sections, models hadronic framework and organization • Elastic scattering • Inelastic scattering n From rest to high energy • Reference Physics Lists Geant 4 course, Annecy 2008 Gunter Folger / CERN 2

Introduction • Hadronic interaction is interaction of hadron with nucleus n strong interaction • QCD is theory for strong interaction, so far no solution at low energies • Simulation of hadronic interactions relies on n Phenomenologial models, inspired by theory Parameterized models, using data and physical meaningful extrapolation Fully data driven approach • Applicability of models in general are limited n n n range of energy Incident particles types Some to a range of nuclei Geant 4 course, Annecy 2008 Gunter Folger / CERN 3

Hadronic Processes, Models, and Cross Sections • Hadronic process may be implemented n n directly as part of the process, or in terms of models and cross sections particle • For models and cross sections there often is a choice of models or datasets process n at rest Physics detail vs. cpu performance manager process 1 in-flight process 2 process 3 • Choice of models and cross section dataset possible via n n Mangement of cross section store Model or energy range manager Geant 4 course, Annecy 2008 model 1 Energy model 2 range. manager. model n Gunter Folger / CERN c. s. set 1 Cross c. s. set 2 section. data. c. s. set n store 4

Cross Sections • Default cross section sets are provided for each type of hadronic process for all hadrons n n elastic, inelastic, fission, capture can be overridden or completely replaced • Different types of cross section sets n n n some contain only a few numbers to parameterize cross section some represent large databases some are purely theoretical Geant 4 course, Annecy 2008 Gunter Folger / CERN 5

Alternative Cross Sections • Low energy neutrons n n G 4 NDL available as Geant 4 distribution data files Available with or without thermal cross sections • “High energy” neutron and proton reaction n 14 Me. V < E < 20 Ge. V, Axen-Wellisch systematics Barashenkov evaluation ( up to 1 Te. V) Simplified Glauber-Gribov Ansatz ( E > ~Ge. V ) • Pion reaction cross sections n n Barashenkov evaluation (up to 1 Te. V) Simplified Glauber-Gribov Ansatz (E > ~Ge. V ) • Ion-nucleus reaction cross sections n Good for E/A < 10 Ge. V • In general, except for G 4 NDL, no cross section for specific final states provided n User can easily implement cross section and model Geant 4 course, Annecy 2008 Gunter Folger / CERN 6

Cross Section Management Get. Cross. Section() sees last set loaded for energy range Load sequence Set 4 Set 3 Set 2 Set 1 Baseline Set Energy Geant 4 course, Annecy 2008 Gunter Folger / CERN 7

Modeling interactions Geant 4 course, Annecy 2008 Gunter Folger / CERN 8

Hadronic Models – Data Driven • Characterized by lots of data n n cross section angular distribution multiplicity etc. • To get interaction length and final state, models interpolate data n cross section, coefficients of Legendre polynomials • Examples n neutrons (E < 20 Me. V) coherent elastic scattering (pp, nn) Radioactive decay Geant 4 course, Annecy 2008 Gunter Folger / CERN 9

Hadronic Models - Parameterized • Depend mostly on fits to data and some theoretical distributions • Examples: n Low Energy Parameterized (LEP) for < 50 Ge. V High Energy Parameterized (HEP) for > 20 Ge. V Each type refers to a collection of models Both derived from GHEISHA model used in Geant 3 n Core code: n n n p p p hadron fragmentation cluster formation and fragmentation nuclear de-excitation Geant 4 course, Annecy 2008 Gunter Folger / CERN 10

Hadronic Models – Theory Driven • Based on phenomenological theory models n n less limited by need for detailed experimental data Experimental data used mostly for validation • Final states determined by sampling theoretical distributions or parameterizations of experimental data • Examples: n n quark-gluon string (projectiles with E > 20 Ge. V) intra-nuclear cascade (intermediate energies) nuclear de-excitation and breakup chiral invariant phase space (up to a few Ge. V) Geant 4 course, Annecy 2008 Gunter Folger / CERN 11

Hadronic Model Inventory sketch, not all shown CHIPS At rest Absorption K, anti-p CHIPS (gamma) Photo-nuclear, electro-nuclear High precision neutron Evaporation Pre. Fermi breakup compound Multifragment Photon Evap Binary cascade Rad. Decay FTF String (up to 100 Te. V) QG String (up to 100 Te. V) Bertini cascade Fission LE pp, pn HEP ( up to 15 Te. V) LEP 1 Me. V 10 Me. V Geant 4 course, Annecy 2008 100 Me. V 1 Ge. V 10 Ge. V Gunter Folger / CERN 100 Ge. V 1 Te. V 12

Model Management Model returned by Get. Hadronic. Interaction() 1 1+3 3 Error 2 Error 2 Model 5 Model 3 Model 4 Model 1 Model 2 Energy Geant 4 course, Annecy 2008 Gunter Folger / CERN 13

Hadronic Model Organization At rest Cross sections Proces s In flight Models Direct implementations Isotope Event production biasing Direct Theory framework impl. High Spallation framework energy Transport Precompoun Cascad String Direct impl. d e utility parton Evaporation Direct String fragmenation Direct impl. util. impl. Direct Frag function intfc impl. Frag function impl. Direct impl. Geant 4 course, Annecy 2008 Gunter Folger / CERN 14

Hadron Elastic Scattering (1) • G 4 Hadron. Elastic. Process n Used in LHEP, uses G 4 LElastic • G 4 UHadron. Elastic. Process n Uses G 4 Hadron. Elastic model • G 4 Hadron. Elastic, combined model n n P, n use G 4 QElastic Pion with E > 1 Ge. V use G 4 HElastic G 4 LElastic otherwise Options available to change settings, expert use Geant 4 course, Annecy 2008 Gunter Folger / CERN 15

Hadron Elastic Scattering (2) • G 4 LElastic, origin in Gheisha models n n Simple parameterization of cross sections and angular distribution Applicable for all long lived hadrons at all energies • G 4 QElastic n n New parameterization of cross section in function of E, t, (A, Z); t is momentum transfer (p – p’)2 (Mandelstam variable) Applicable for proton and neutron at all energies • G 4 Diffuse. Elastic n n Scattering particle (wave) on nucleus viewed as black disk with diffuse edge Applicable p, n, pi, K, lambda, … • G 4 HElastic n n Glauber model for elastic scattering Applicable for all stable hadrons • G 4 LEpp/G 4 LEnp n n taken from detailed phase-shift analysis for (p, p), (n, n)/(n, p), (p, n) : , good up to 1. 2 Ge. V Geant 4 course, Annecy 2008 Gunter Folger / CERN 16

Inelastic Interactions Geant 4 course, Annecy 2008 Gunter Folger / CERN 17

Hadronic Interactions from Te. V me. V Te. V hadron d. E/dx ~ A 1/3 Ge. V ~100 Me. V - ~10 Me. V Geant 4 course, Annecy 2008 ~ Ge. V - ~100 Me. V ~10 Me. V to thermal Gunter Folger / CERN 18

At Rest • Most Hadrons are unstable n n Only proton and anti-proton are stable! I. e hadrons, except protons have Decay() • Negative particles and neutrons can be captured (neutron, μ-), absorbed (π -, K-) by, or annihilate (anti-proton, antineutron) in nucleus n In general this modeled as a two step reaction p p Particle interacts with nucleons or decays within nucleus Exited nucleus will evaporate nucleons and photons to reach ground state Geant 4 course, Annecy 2008 Gunter Folger / CERN 19

Capture Processes • At Rest Capture Processes n n n G 4 Muon. Minus. Capture. At. Rest G 4 Pion. Minus. Absorption. At. Rest G 4 Kaon. Minus. Absorption G 4 Anti. Proton. Annihilation. At. Rest G 4 Anti. Neutron. Annihilation. At. Rest • Alternative model implemented in CHIPS n G 4 QCapture. At. Rest p Applies to all negative particles, and anti-nucleon • Neutron with E < ~30 Me. V can also be captured n n n G 4 Hadron. Capture. Process uses following models: G 4 LCapture (mainly for neutrons), simple + fast G 4 Neutron. HPCapture (specifically for neutrons), detailed cross sections, slow Geant 4 course, Annecy 2008 Gunter Folger / CERN 20

Using Capture processes // Muon minus a. Proc. Man = G 4 Muon. Minus: : Muon. Minus()->Get. Process. Manager(); G 4 Muon. Minus. Capture. At. Rest * the. Muon. Minus. Absorption = new G 4 Muon. Minus. Capture. At. Rest(); a. Proc. Man->Add. Rest. Process(the. Muon. Minus. Absorption); // Pion. Minus a. Proc. Man = G 4 Pion. Minus: : Pion. Minus()->Get. Process. Manager(); G 4 Pion. Minus. Absorption. At. Rest * the. Pion. Minus. Absorption = new G 4 Pion. Minus. Absorption. At. Rest(); a. Proc. Man->Add. Rest. Process(the. Pion. Minus. Absorption); … etc…, OR using CHIPS process // Using Chips Capture Process a. Proc. Man = G 4 Pion. Minus: : Pion. Minus()->Get. Process. Manager(); G 4 QCapture. At. Rest * h. Process = new G 4 QCapture. At. Rest(); a. Proc. Man ->Add. Rest. Process(h. Process); Geant 4 course, Annecy 2008 Gunter Folger / CERN 21

Low energy neutron transport Neutron. HP • Data driven models for low energy neutrons, E< 20 Me. V, down to thermal n Elastic, capture, inelastic, fission p n Inelastic includes several explicit channels Based on data library derived from several evaluated neutron data libraries Geant 4 course, Annecy 2008 Gunter Folger / CERN 22

How to Use G 4 Processmanager * proc. Man = G 4 Neutron: : Neutron()->Get. Process. Manager; G 4 Hadron. Elastic. Process * a. P = new G 4 Hadron. Elastic. Process G 4 Neutron. HPElastic * HPElastic = new G 4 Neutron. HPElastic; HPElastic->Set. Min. Energy(0); HPElastic->Set. Max. Energy(20*Me. V); G 4 Neutron. HPElastic. Data* HPElastic. Data = new G 4 Neutron. HPElastic. Data; a. P->Add. Data. Set(HPElastic. Data); a. P->Register. Me(HPElastic); Proc. Man->Add. Discrete. Process(a. P); … etc for the other processes Geant 4 course, Annecy 2008 Gunter Folger / CERN 23

Precompound Model • G 4 Pre. Compound. Model is used for nucleonnucleus interactions at low energy and as a nuclear de-excitation model within higherenergy codes n n n valid for incident p, n from 0 to 170 Me. V takes a nucleus from a highly-excited set of particle-hole states down to equilibrium energy by emitting p, n, d, t, 3 He, alpha once equilibrium state is reached, four other models are invoked via G 4 Excitationandler to take care of nuclear evaporation and breakup p these models not currently callable by users • The parameterized and cascade models all have nuclear de-excitation models embedded Geant 4 course, Annecy 2008 Gunter Folger / CERN 24

Using the Pre. Compound. Model G 4 Processmanager * proc. Man = G 4 Neutron: : Neutron()->Get. Process. Manager; // equilibrium decay G 4 Excitation. Handler* the. Handler = new G 4 Excitation. Handler; // preequilibrium G 4 Precompound. Model* pre. Model = new G 4 Precompound. Model(the. Handler); //Create equilibrium decay models and assign to Precompound model G 4 Neutron. Inelastic. Process* n. Proc = new G 4 Neutron. Inelastic. Process; // Register model to process, process to particle n. Proc->Register. Me(pre. Model); proc. Man->Add. Discrete. Process(n. Proc); Geant 4 course, Annecy 2008 Gunter Folger / CERN 25

Cascade models ( 100 Me. V – Ge. Vs ) Geant 4 course, Annecy 2008 Gunter Folger / CERN 26

Bertini Cascade Model • The Bertini model is a classical cascade: n n n it is a solution to the Boltzman equation on average no scattering matrix calculated can be traced back to some of the earliest codes (1960 s) • Core code: n n elementary particle collider: uses free-space cross sections to generate secondaries cascade in nuclear medium pre-equilibrium and equilibrium decay of residual nucleus 3 -D model of nucleus consisting of shells of different nuclear density • In Geant 4 the Bertini model is currently used for p, n, L , K 0 S , + n valid for incident energies of 0 – 10 Ge. V Geant 4 course, Annecy 2008 Gunter Folger / CERN 27

Using the Bertini Cascade G 4 Cascade. Interface* bertini = new G 4 Cascade. Interface() G 4 Proton. Inelastic. Process* pproc = new G 4 Proton. Inelastic. Process(); pproc -> Register. Me(bertini); proton_manager -> Add. Discrete. Process(pproc); Geant 4 course, Annecy 2008 Gunter Folger / CERN 29

Binary Cascade • Modeling sequence similar to Bertini, except that n n Nucleus consists of nucleons hadron-nucleon collisions p p n n handled by forming resonances which then decay according to their quantum numbers Elastic scattering on nucleons particles follow curved trajectories in nuclear potential Pre. Compound model is used for nuclear de-excitation after cascading phase • In Geant 4 the Binary cascade model is currently used for incident p, n and n n valid for incident p, n from 0 to 10 Ge. V valid for incident from 0 to 1. 3 Ge. V • A variant of the model, G 4 Binary. Light. Ion. Reaction, is valid for incident light ions n or higher if target is made of light nuclei Geant 4 course, Annecy 2008 Gunter Folger / CERN 30

Using the Binary Cascade Invocation sequence Binary cascade G 4 Binary. Cascade* binary = new G 4 Binary. Cascade(); G 4 Proton. Inelastic. Process* pproc = new G 4 Proton. Inelastic. Process(); pproc -> Register. Me(binary); proton_manager -> Add. Discrete. Process(pproc); Invocation sequence Binary. Light. Ion. Reaction G 4 Binary. Light. Ion. Reaction* ion. Binary = new G 4 Binary. Light. Ion. Reaction; G 4 Ion. Inelastic. Process* ion. Proc = new G 4 Ion. Inelastic. Process; ion. Proc->Register. Me(ion. Binary); generic. Ion. Manager->Add. Discrete. Process(ion. Proc); Geant 4 course, Annecy 2008 Gunter Folger / CERN 31

Liege Cascade model • Well established code in nuclear physics n n Well tested for spallation studies Uses ABLA code for nuclear de-excitation • Valid for p, n, pions up to 2 -3 Ge. V n Not applicable to light nuclei ( A< 12 -16) • Authors collaborate with Geant 4 to rewrite code in C++ n n First version will be released with 9. 2 in December 2008 ABLA is included as well Geant 4 course, Annecy 2008 Gunter Folger / CERN 32

LEP, HEP models • Parameterized models, based on Gheisha • Modeling sequence: n n n initial interaction of hadron with nucleon in nucleus highly excited hadron is fragmented into more hadrons particles from initial interaction divided into forward and backward clusters in CM another cluster of backward going nucleons added to account for intra-nuclear cascade clusters are decayed into pions and nucleons remnant nucleus is de-excited by emission of p, n, d, t, alpha • The LEP and HEP models valid for p, n, , t, d • LEP valid for incident energies of 0 – ~30 Ge. V • HEP valid for incident energies of ~10 Ge. V – 15 Geant 4 course, Annecy 2008 Gunter Folger / CERN 34

Using the LEP and HEP models G 4 Proton. Inelastic. Process* pproc = new G 4 Proton. Inelastic. Process(); G 4 LEProton. Inelastic* LEproton = new G 4 LEProton. Inelastic(); G 4 HEProton. Inelastic* HEproton = new G 4 HEProton. Inelastic(); HEproton -> Set. Min. Energy(25*Ge. V); LEproton -> Set. Max. Energy(25*Ge. V); pproc -> Register. Me(LEproton); pproc -> Register. Me(HEproton); proton_manager -> Add. Discrete. Process(pproc); Geant 4 course, Annecy 2008 Gunter Folger / CERN 35

String Models – QGS and FTF • For incident p, n, π, K n QGS model also for high energy when CHIPS model is connected • QGS ~10 Ge. V < E < 50 Te. V • FTF ~ 4 Ge. V < E < 50 Te. V • Models handle: n n n selection of collision partners splitting of nucleons into quarks and diquarks formation and excitation of strings • String hadronization needs to be provided • Damaged nucleus remains. Another Geant 4 model must be added for nuclear fragmentation and de-excitation n pre-compound model, CHIPS for nuclear fragmentation Binary Cascade and precompound for re-scattering and deexcitation Geant 4 course, Annecy 2008 Gunter Folger / CERN 36

String Model Algorithm • • Build up 3 -dimensional model of nucleus Large -factor collapses nucleus to 2 dimensions Calculate impact parameter with all nucleons Calculate hadron-nucleon collision probabilities n use Gaussian density distributions for hadrons and nucleons • Form strings • String formation and fragmentation into hadrons Geant 4 course, Annecy 2008 Gunter Folger / CERN 37

Quark Gluon String Model • Two or more strings may be stretched between partons within hadrons n strings from cut cylindrical Pomerons • Parton interaction leads to color coupling of valence quarks n sea quarks included too • Partons connected by quark gluon strings, which hadronize Geant 4 course, Annecy 2008 Gunter Folger / CERN 38

Fritiof Model • String formation via scattering of projectile on nucleons n n momentum is exchanged, increases mass of projectile and/or nucleon Sucessive interactions further increase projectile mass Excited off shell particle viewed as string Lund string fragmentation functions used • FTF model has been significantly improved in the last year Geant 4 course, Annecy 2008 Gunter Folger / CERN 39

Longitudinal String Fragmentation • String extends between constituents • Break string by inserting q-qbar pair according to n u : d : s : qq = 1 : 0. 27 : 0. 1 • At break -> new string + hadron • Created hadron gets longitudinal momentum from sampling fragmentation functions • Gaussian Pt , <Pt> = 0. 5 Ge. V Geant 4 course, Annecy 2008 Gunter Folger / CERN 40

Using QGS or FTF model G 4 Theo. FSGenerator * the. HEModel = new G 4 Theo. FSGenerator(); G 4 FTFModel * the. String. Model = new G 4 FTFModel(); G 4 Excited. String. Decay * the. String. Frag = new G 4 Excited. String. Decay(new G 4 Lund. String. Fragmentation()); the. String. Model->Set. Fragmentation. Model(the. String. Frag); the. HEModel->Set. Transport(new G 4 Binary. Cascade()); the. HEModel->Set. Min. Energy(4. *Ge. V); the. HEModel->Set. Max. Energy(100*Te. V); the. HEModel->Set. High. Energy. Generator(the. String. Model); // reduce use of casacde to below 5 Ge. V // the. Casacde. Model->Set. Max. Energy(5*Ge. V); proton. Inelasticprocess->Register. Me(the. HEModel); Geant 4 course, Annecy 2008 Gunter Folger / CERN 41

Chiral Invariant Phase Space (CHIPS) • Origin: M. V. Kosov (CERN, ITEP) • Use: n n capture of negatively charged hadrons at rest anti-baryon nuclear interactions gamma- and lepto-nuclear reactions back end (nuclear fragmentation part) of QGSC model Geant 4 course, Annecy 2008 Gunter Folger / CERN 42

Chiral Invariant Phase Space (CHIPS) • Quasmon: an ensemble of massless partons uniformly distributed in invariant phase space n a 3 D bubble of quark-parton plasma n can be any excited hadron system or ground state hadron • u, d, s quarks treated symmetrically (all massless) • Critical temperature TC : model parameter which relates the quasmon mass to the number n of its partons: n M 2 Q = 4 n(n-1)T 2 C => MQ ~ 2 n. TC n TC = 180 – 200 Me. V • Quark fusion hadronization: two quark-partons may combine to form an on-mass-shell hadron • Quark exchange hadronization: quarks from quasmon and neighbouring nucleon may trade places Geant 4 course, Annecy 2008 Gunter Folger / CERN 43

Skipping • Electro-nuclear interacions • Ion induced interactions n n Already mentioned Binary light ion cascade QMD model under development Wilson Abrasion/Ablation models available EM Dissociation model • Isotope production model • Radioactive decay Geant 4 course, Annecy 2008 Gunter Folger / CERN 45

Summary hadronics • Geant 4 hadronic physics allows user to choose how a physics process should be implemented: cross sections n models • Many processes, models and cross sections to choose from n hadronic framework makes it easier for users to add his own cross section or model • Recent improvements new additions in n FTF model n Precompound and de-execitation models n New Liege cascade implemenation, including ABLA n Elastic scattering n Cross sections n Geant 4 course, Annecy 2008 Gunter Folger / CERN 46

Physics Lists • Hadronic Physics lists provided by Geant 4 n n help users in difficult task to compose a complete and consistent set of cross sections, processes, and models for all particles Rely on experience of hadronic developers • Advanced examples provide lists for specific cases • Reference physics lists attempt to cover many use cases Geant 4 course, Annecy 2008 Gunter Folger / CERN 47

Reference Physics Lists (1) • Reference physics lists attempt to cover a wide range of use cases n Extensive validation by LHC experiments for simulation hadronic showers p p n Comparison to TARC experiment testing neutron production and transport demonstrates good agreement p n QGSP_BERT, or QGSP_BERT_EMV current favorite New FTF_BIC is promising alternative QGSP_BIC_HP, QGSP_BERT_HP user feedback, e. g. vi hypernews, is welcome • Users responsible for validating results • Documentation available from user support page • Physics Lists User forum for questions and feedback Geant 4 course, Annecy 2008 Gunter Folger / CERN 48

Reference physics lists (2) • Reference Physics Lists use modular design n n Reuse builders for several physics lists Evolve lists following developments in G 4 p p New options first offered in experimental lists Adopting mature options in production lists • Sharing of physics lists between users n n LHC experiments required common physics settings supported by G 4 Sharing of experience, validation, etc… Geant 4 course, Annecy 2008 Gunter Folger / CERN 49

Using Reference physics • In Main, pass a physics list to run. Manager: G 4 VUser. Physics. List* physics = new FTF_BIC; run. Manager->Set. User. Initialization(physics); Geant 4 course, Annecy 2008 Gunter Folger / CERN 50

Summary – Physics Lists • Physics list provided and supported by Geant 4 n n n Help users Share experience Reduce risk of missing physics, p or using wrong models for specific type of application Geant 4 course, Annecy 2008 Gunter Folger / CERN 51

Summary • Hadronic physics offers models use n n n Parameterized modeling Detailed theory inspired models Precise data driven models • Offer choice of physics detail, n at expense of CPU performance • Continuing improvement in modeling • Physics lists help users chosing hadronic physics • Did not show n n Extensive validation effort going on in hadronics See still incomplete list in: http: //geant 4. fnal. gov/hadronic_validation/validation_plots. htm Geant 4 course, Annecy 2008 Gunter Folger / CERN 52

Backup slides Geant 4 course, Annecy 2008 Gunter Folger / CERN 53