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

Status and Plans for Geant4 Hadronics

Dennis Wright (SLAC)

SPENVIS & Geant4 Space Users' WorkshopLeuven, Belgium3-7 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 restprocess 1

in-flightprocess 2

process3

processn

model 1model 2

.

.model n

c.s. set 1c.s. set 2

.

.c.s. set n

Cross sectiondata 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 EvapMultifragmentFermi breakup

Fission

EvaporationPre-

compound

Bertini cascade

Binary cascadeQG 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)

CHIPSHadronic 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 12C 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 - 400 MeV/n 12C on Pb

Neutron production - 400 MeV/n 40Ar on Pb


● 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


● 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


● Radioactive Decay Process– designed to provide -decayselectron capture,

isomeric transition– decay table entries with short lifetimes need to be completed

● examples: 8Be, 5Li● need to add decay mode, daughter excitation energy, intensity

– add proton and delayed neutron decay channels● examples: 6Be, 7B

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


● 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


● 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


● 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-


● 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


● 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


● 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 < 4, A > 208

– slower

– requires cross section table to be downloaded

Elastic proton scattering from 28Si (1 GeV)

Elastic proton scattering from 4He (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, +,L0

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

Documents

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