Adding Kaons to the Bertini Cascade Model

Dennis Wright (SLAC) and Aatos Heikkinen (HIP)Interlaken, Switzerland

27th September - 1st October, 2004

Outline

● Reasons for the extension

● How the model was extended

– elementary cross sections

– number of particle types treated

– code changes

● Early results

● Plans

– improvements, further extensions

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Reasons to Extend the Bertini Cascade

● No existing Geant4 hadronic model does a reasonable job handling strange particle interactions at 0 < E < 5 GeV

– only LEP model handles kaons at all in this region

● Low energy kaons (and other strange particles) are important for BaBar and hadron calorimetry in higher energy experiments

● Bertini cascade has been demonstrated to work fairly well for pions and nucleons

● Bertini cascade model is relatively easy to extend to strange particles

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Adding New Cross Sections

● Model assumes particles travel through a nucleus and interact with nucleons according the free particle cross sections

– Need K+ p, K+ n, K- p, K- n cross sections from 0 to 15 GeV

– For subsequent intra-nuclear interactions need everything else:

● K0, K0bar, ignored)● no resonances

● many cross sections available from CERN particle catalogs

– many others ( K0 p, n, ... ) require isospin arguments, guesswork

● K0 p = K+ n● K0bar n = K- p

– up to 7-body final states are important (and have been measured)

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Code Changes● New classes

– G4CascadeKplusNChannel, G4CascadeLambdaPChannel, ...

– Contain final state particle types, elementary cross section, multiplicity data from T = 0 – 15 GeV

● Add strange particle branches for generation of multiplicity and final states

– G4ElementaryParticleCollider

– G4NucleiModel

● Other classes changed:

– G4InuclElementaryParticle

– G4CascadeInterface

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Significant non-changes

● Use existing angular distribution parameterizations

● Use existing final state momentum partition parameterizations

● Use existing pion nuclear potential (hard-sphere 7 MeV deep)

● No nucleon-nucleon correlations added for kaons

● Strange particle production (by incident pi, n, p) not added

● No resonances added

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Early Results

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Early Results

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Early Results

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Early Results

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Improvements

● Find better nuclear potentials for K,– Should be deeper

● Install pi, p, n – induced strange particle production

– cross sections exist ● If correlations are important, add absorption on quasi-

deuterons

● Parameterize and use measured angular distributions for finals states induced by kaons

● Extend to incident hyperons?

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