Status and Plans for Geant4 Hadronics Dennis Wright (SLAC) SPENVIS & Geant4 Space Users' Workshop Leuven, Belgium 3-7 October 2005

Outline ● Brief introduction to Geant4 hadronics ● Development plans – of interest to the space applications community ● ion interactions ● radioactive decay – of general interest ● Low Energy Parameterized model improvements ● Chiral Invariant Phase Space (CHIPS) model extensions ● extending high energy models ● Hadronic highlights of the 7.1 release

Hadronic Physics in Geant4 ● User is responsible for building an appropriate physics list – select particles to use – add processes to particles – register models to processes ● Geant4 in general and G4 hadronic physics in particular provides much freedom in this – this is a mixed blessing! – only 5 hadronic process types to choose from, but ~40 models – current Geant4 policy: no default processes or models ● to a novice user, this can be confusing ● pre-built physics lists partly address this issue

particle at rest process 1 in-flight process 2 process 3 process n model 1 model 2. model n c.s. set 1 c.s. set 2. c.s. set n Cross section data store Energy range manager

1 MeV 10 MeV 100 MeV 1 GeV 10 GeV 100 GeV 1 TeV LEP HEP ( up to 15 TeV) Photon Evap Multifragment Fermi breakup Fission Evaporation Pre- compound Bertini cascade Binary cascade QG String (up to 100 TeV) FTF String (up to 20 TeV) High precision neutron At rest Absorption  K, anti-p Photo-nuclear, electro-nuclear CHIPS (gamma) CHIPS Hadronic Model Inventory LE pp, pn Rad. Decay

Development Plans (relating to space applications) ● Binary light ion cascade model (mass range) – basic assumption limits use to 12 C projectiles and lighter: interaction of “participants” (nucleons in projectile + secondaries from target) is ignored – should be a big effect for heavy projectile – heavy target collisions – we are now studying its extension to higher mass projectiles ● results look promising, despite limiting assumption ● tested for some medium-mass projectiles

Neutron production MeV/n 12 C on Pb

Neutron production MeV/n 40 Ar on Pb

Development Plans (relating to space applications) ● Energy range of ion transport models in Geant4 – current limit of Binary Light Ion cascade is ~ 10 GeV/n – low energy limit is ~80 MeV – other models can go higher ● URQMD ● JQMD ● JAM – but they are currently external to Geant4 ● interfaces exist for JQMD and JAM

Development Plans (relating to space applications) ● High precision neutron models – cannot currently handle all elements – data for Hg, Gd, etc. missing – need to create new entries for high precision neutron data library G4NDL – not found in ENDF, JENDL, etc. – need to collect cross sections, final state multiplicity and angular distributions from 0 – 20 MeV

Development Plans (relating to space applications) ● Radioactive Decay Process – designed to provide  -    decays  electron capture, isomeric transition – decay table entries with short lifetimes need to be completed ● examples: 8 Be, 5 Li ● need to add decay mode, daughter excitation energy, intensity – add proton and delayed neutron decay channels ● examples: 6 Be, 7 B

Development Plans (of general interest) ● Low Energy Parameterized Models – the nuclear de-excitation part of this model is rather simple: ● after the intra-nuclear cascade stage, goes straight to evaporation ● evaporation stage is highly parameterized -> doesn't do as well as other models available at low energies – add more detailed, nucleus-dependent parameterization ● requires looking at evaporation data and re-evaluating the parameterizations – general re-factoring of all LEP code ● still many holdovers from old GHEISHA code

Development Plans (of general interest) ● Bertini cascade – improve angular distributions of kaon-induced, 2-body final states ● these are the channels with the largest cross sections ● also lots of angular distribution data – begin validation of higher energy data ● things look good at 1GeV and below, what about 1 – 10 GeV ? ● some data exist (1 – 3 GeV) ● more coming from test beam experiments

Development Plans (of general interest) ● Bertini cascade – begin testing and validation of elastic and quasi-elastic scattering ● code has so far always been used for inelastic scattering ● it is set up to do elastic, but has not yet been validated ● would be a very useful alternative to the LEP elastic – explore using Bertini cascade for ion-ion collisions ● most of the machinery already exists ● about 1 year required to add necessary code and for testing ● perhaps a useful alternative to Binary Light Ion Cascade

Development Plans (of general interest) ● Binary cascade – propagate interface to string models ● high energy models could then use Binary cascade directly as a de-excitation stage – look at extending to kaons ● difficult problem because the model deals explicitly with resonances, and there are so many when a strange quark is added – look at extending to higher energies ● current limit is 10 GeV for p,n, 1.3 GeV for pi+, pi-

Development Plans (of general interest) ● Chiral Invariant Phase Space (CHIPS) model – currently used for gamma- and electro-nuclear processes ● interface to CHIPS does not conserve charge: virtual photon is converted 50% to pi+, 50% to pi- ● need to interact photon directly with nucleus – look into extending to muon-nuclear processes – look at extending to higher energies ( > 5 GeV) ● CHIPS now used in Geant4 as a nuclear de-excitation model ● could be used to replace quark-gluon string model ● use a quasmon string (Herwig-style fragmentation) instead of quark-gluon string (Pythia-style fragmentation)

CHIPS Quasmon (as used in Electro-nuclear model) *

Development Plans (longer term) ● Neutrino interactions – becoming more important now that large detectors are coming into operation – CHIPS model to be used to implement interactions ● incoming neutrino interacts with a nucleon, forming a quasmon ● quasmon decays into hadrons – energy limit ~5 GeV incident

Development Plans (longer term) ● High energy models – re-factor high energy parameterized model (remove vestiges of GHEISHA) – extend QGS, FTF models ● current upper limit is ~ TeV ● but no Geant4 model has yet incorporated minijets -> effectively limits validated energy to 100 GeV ● consider adding code from HE event generators, such as DPMJET which can go to 2000 TeV

Development Plans (longer term) ● Multiple scattering of hadrons – currently Geant4 treats all processes independently – no interference between hadron and EM processes – interference effects could be as large as 100% – code design problem ● interdependency between EM and hadronic sectors now required

Highlights: Coherent elastic hadron scattering from nuclei ● Introduced in the 7.0 release ● Improved angular distributions for heavy targets and larger angles added in 7.1 ● A better alternative to the LEP elastic model, but: – effective lower energy limit = 1 GeV – not valid for A 208 – slower – requires cross section table to be downloaded

Elastic proton scattering from 28 Si (1 GeV)

Elastic proton scattering from 4 He (301 GeV)

Highlights: Extension of Bertini cascade model to strange particles ● requires pre-compiler flag G4BERTINI_KAON to be set when building Geant4 libraries ● now valid for: – p, n,  +,         L  0 S  +,  -,  0,  -,  - –  GeV ● A better alternative to the LEP elastic model for low and intermediate energies

705 MeV/c K+ quasi-elastic scattering from C

705 MeV/c K+ quasi-elastic scattering from Pb

Highlights: Fixes and Tuning ● Memory leaks fixed in: – RadioactiveDecay – De-excitation handler – Abrasion/Ablation model ● Physics tuning of CHIPS model for anti-proton annihilation at rest ● Isotope production code now supplies name of hadronic model that produced it ● Corrected momentum balance for elastic scattering final states

Summary ● Development plans – extending ion interaction codes to higher mass nuclei – add decay information and new decay modes to radioactive decay table – continued improvement of LEP, Bertini and Binary cascade models – expanded use of CHIPS model for mu-nuclear, neutrino and high energy modeling ● Release 7.1 highlights – new, improved elastic scattering model (coherent elastic) – kaon extension of Bertini cascade model