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Th. Gaitanos, H. Lenske, U. Mosel

Production of fragments with finite strangeness in heavy-ion collisions within a BUU+SMM combined model. Th. Gaitanos, H. Lenske, U. Mosel. Introduction Theoretical aspects Formation of relativistic hypernuclei in simulations Non-equlibrium transport dynamics (GiBUU)

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Th. Gaitanos, H. Lenske, U. Mosel

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  1. Production of fragments with finite strangeness in heavy-ion collisions within a BUU+SMM combined model Th. Gaitanos, H. Lenske, U. Mosel • Introduction • Theoretical aspects • Formation of relativistic hypernuclei in simulations • Non-equlibrium transport dynamics (GiBUU) • Fragmentation mechanism (coalescence, statistical approaches, e.g. SMM) • Hybrid approach (GiBUU+SMM) • Applications • Benchmark: X+X@SIS/GSI, spectator fragmentation (ALADIN) • X+X@2AGeV (HypHI), p+X@50GeV, X+X@20AGeV (J-PARC) • Final remarks

  2. Introduction… • Knowledge of YN & YY interaction (strangeness sector of hadronic EoS) ? • important for physics of neutron stars • „Hyperon Stars“, ~60% neutron, but ~20% occupation of protons and strange baryons • (N.K. Glendenning, astro-ph/9707.351v1; F. Weber et. al., astro-ph/0705.2708v2) • So far mainly from nuclear structure studies • Info on properties of strange baryons in neutron rich matter needed •  e.g. (exotic) hypernuclei, e.g. 3HeY, 5HeY (Y=L,S) • Formation of (exotic?) hypernuclei accessible in high-energy reactions (p+X, X+X) • HypHI: 12C(6Li)+12C@SIS (in progress…) • J-PARC: p+12C@50GeV, 12C+12C@20AGeV (in future…) • PANDA: Antiproton-Nucleus (in future…)

  3. K L L,S,p,K,... L p p L L L,S,p,K,... K Relativistic Hypernuclei… • Production of Hypernuclei in Relativistic HIC • Production of many hyperons • Secondary rescattering (pNYK) • Multiple coalescence of hyperons with fragments • Theoretical Framework • Phase-Space evolution • Transport equations of Boltzmann type, e.g. Giessen-BUU model •  http://www.physik.uni-giessen.de/GiBUU/ • Description of fragment formation ? • Statistical picture (SMM, A.Botvina & I.Mishustin), coalescence • Description of hypernuclei formation? • simple coalescence in coordinate (Y inside fragmenting source) and in momentum space

  4. Dynamical aspects in X+X reactions (Spectators)… • Def. ofSpectators • Y(0)>0.75 (ALADIN)+r<rsat/100 • Spectators • Well defined conditions after onset of instability… • Anisotropy • …and onset of equilibration

  5. Benchmark: X+X reactions (spectator fragmentation in Au+Au@SIS)… Reasonable description of spectator fragmentation Data: ALADIN-collaboration

  6. 12C+12C@2AGeV (HypHI)… Formation of hypernuclei from spectator fragmentation via coalescence (here only in coordinate space, e.g. condition: Y inside radius of fragmenting source) Note: extremely low total yields, e.g. orders of only view mb for light He-hypernuclei Consistent with previous studies: M.Wakai, NPA547(92)89c Very small systemsless compressionless pions available for rescattering inside spectators Very small systemssmall interaction radius for pions passing through spectator

  7. p+12C@50GeV (J-PARC) – dynamical aspects… Two sources (residual target+moving source) Stable conditions after resonance decay Most of hyperons created & rescatter inside moving source

  8. p+12C@50GeV (J-PARC) – theor. estimations on hypernuclei… Hypernuclei: Simple coalescence (Y inside source‘s) Prediction: production of energetic hypernuclei (Similar results for 12C+12C@20AGeV)

  9. Final remarks & Outlook… • Heavy-Ion Collissions •  Fragmentation in spectator matter • min. compression/expansion effects, almost no radial flow effects •  Wide selection of experimental data (ALADIN/INDRA) •  Useful tool in studying formation of hypernucei in spectator fragmentation • Hybrid approach (GiBUU+SMM) •  pre-equilibrium dynamics: relativistic GiBUU •  asymptotic equilibrated stage: • statistical decay by means of SMM for spectator matter • (break-up of fireball within coalescence picture due to rapid expansion) • Theoretical estimation for future HypHI & J-PARC experiments •  Xsections of light hypernucei from spectators in 12C+12C@2AGeV •  Xsections of energetic light hypernuclei in p+12C@50GeV • Future/under progress developments •  More consistent treatment of formation of hypernuclei, e.g. • recently extended SMM-code including strangeness degrees of freedom • (A. Botvina & J. Pochodzalla)

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