Hadronic Physics III Geant4 Tutorial at Marshall Space Flight Center 19 April 2012 Dennis Wright (SLAC) Geant4 9.5

Outline Gamma- and lepto-nuclear models based on CHIPS model based on Bertini QCD string models Quark-gluon string (QGS) model Fritiof (FTF) model Other models CHIPS capture fission 2

Gamma- and Lepto-nuclear Processes Geant4 models which are neither exclusively electromagnetic nor hadronic gamma-nuclear electro-nuclear muon-nuclear Geant4 processes available: G4PhotoNuclearProcess (implemented by two models) G4ElectronNuclearProcess (implemented by one model) G4PositronNuclearProcess (implemented by one model) G4MuonNuclearProcess (implemented by two models) 3

Gamma- and Lepto-nuclear Processes Gammas interact directly with the nucleus at low energies they are absorbed and excite the nucleus as a whole at high energies they act like hadrons (pion, rho, etc.) and form resonances with protons and neutrons Electrons and muons cannot interact hadronically, except through virtual photons electron or muon passes by a nucleus and exchanges virtual photon virtual photon then interacts directly with nucleus (or nucleons within nucleus) 4

Gamma- and Lepto-nuclear Models 5 Gamma-nuclear Lepto-nuclear   s and nucleons e-e- virtual 

Gamma- and Lepto-nuclear Models G4VDMuonNuclear Bertini cascade at low and medium energies (E < 10 GeV) FTFP at high energies (E > 10 GeV) for both constituent models gamma is treated as a pion will soon have direct gamma interaction G4GammaNuclearReaction alternate to G4VDMuonNuclear based on CHIPS (chiral invariant phase space) model direct gamma interaction G4ElectroNuclearReaction CHIPS-based model for electrons, positrons 6

QCD String Models Fritiof (FTF) valid for p, n, , K, ,  from 3 GeV to ~TeV anti-proton, anti-neutron, anti-hyperons at all energies anti-d, anti-t, anti- 3 He, anti-  with momenta between 150 MeV/nucleon and 2 GeV/nucleon Quark-Gluon String (QGS) valid for p, n, , K from 15 GeV to ~TeV Both models handle: building 3-D model of nucleus from individual nucleons splitting nucleons into quarks and di-quarks formation and excitation of QCD strings string fragmentation and hadronization 7

How the QCD String Model Works (FTF Case) Lorentz contraction turns nucleus into pancake All nucleons within 1 fm of path of incident hadron are possible targets Excited nucleons along path collide with neighbors n + n  n , NN,  essentially a quark-level cascade in vicinity of path  Reggeon cascade All hadrons treated as QCD strings projectile is quark-antiquark pair or quark-diquark pair target nucleons are quark-diquark pairs 8

How the QCD String Model Works (FTF Case) Hadron excitation is represented by stretched string string is set of QCD color lines connecting the quarks When string is stretched beyond a certain point it breaks replaced by two shorter strings with newly created quarks, anti- quarks on each side of the break High energy strings then decay into hadrons according to fragmentation functions fragmentation functions are theoretical distributions fitted to experiment Resulting hadrons can then interact with nucleus in a traditional cascade 9

High Energy Nuclear Interaction 10 excited string nucleon projectile

QGS Validation 11

FTF Validation 12

FTF Anti-deuteron Scattering 13

CHIPS (Chiral Invariant Phase Space) Model Model originally used to de-excite nuclei after high energy interaction has since been extended for use in stopping processes and gamma- and electro-nuclear models experimental versions apply to high energy and ion-ion Basic model principles: u, d, s quarks all treated as massless (hence chiral invariant) when two hadrons interact, a bag of partons is formed, all of which are distributed uniformly in phase space this bag is called a “quasmon” and decays somewhat thermodynamically as partons fuse to form hadrons 14

 - Stopping in Nucleus (CHIPS) 15 quasmon disappears nuclear evaporation begins   clusters of nucleons quasmon hadron escapes nucleus

Capture Processes and Models G4PionMinusAbsorptionAtRest process with direct implementation (no model class) G4PionMinusAbsorptionBertini ** at rest process implemented with Bertini cascade model G4KaonMinusAbsorption at rest process with direct implementation G4AntiProtonAnnihilationAtRest process with direct implementation G4FTFCaptureAtRest ** process implemented for anti-protons by FTF model ** recommended 16

Capture Processes and Models G4MuonMinusCaptureAtRest process with direct implementation (no model class) G4QCaptureAtRest alternative to above, using CHIPS model G4AntiNeutronAnnihilationAtRest process with direct implementation G4HadronCaptureProcess in-flight capture for neutrons model implementations: G4LCapture : all incident energies G4NeutronHPCapture (below 20 MeV) 17

Fission Processes and Models G4HadronFissionProcess can use two models G4LFission (mostly for neutrons) G4NeutronHPFission (specifically for neutrons below 20 MeV) A third model handles spontaneous fission as an inelastic process (rather than fission) G4FissLib: Livermore Spontaneous Fission 18

Isotope Production Special process originally designed to register recoil nuclei after any interaction Now mostly outdated except if you use the LEP models those models don’t produce recoil nuclei Now implemented as a model running specifically with LEP code To use: G4LENeutronInelastic* nmodel = new G4LENeutronInelastic; G4NeutronIsotopeProduction* prodModel = new G4NeutronIsotopeProduction; nmodel->RegisterIsotopeProductionModel(prodModel); 19

Summary Gamma-nuclear and lepto-nuclear processes are available for nuclear reactions initiated by non-hadrons Two QCD string models are available for implementing high energy interactions Fritiof (FTF) : the more versatile, covers many particle types, larger energy range Quark-Gluon String (QGS) Several stopping processes and models available for , , K, anti-p, anti-n CHIPS for stopping and nuclear de-excitation Capture and fission (mostly for neutrons) ConstructGeneral(); // method may be defined by user to hold all other processes } 20