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Production of fragments with finite strangeness in reactions wihtin a GiBUU+SMM combined approach. Th. Gaitanos, H. Lenske, U. Mosel. Introduction Theoretical aspects Formation of relativistic hypernuclei in simulations Non-equlibrium transport dynamics (Giessen-BUU)

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production of fragments with finite strangeness in reactions wihtin a gibuu smm combined approach
Production of fragments with finite strangeness in reactions wihtin a GiBUU+SMM combined approach

Th. Gaitanos, H. Lenske, U. Mosel

  • Introduction
  • Theoretical aspects
  • Formation of relativistic hypernuclei in simulations
  • Non-equlibrium transport dynamics (Giessen-BUU)
  • Fragmentation mechanism (coalescence, statistical approaches, e.g. SMM)
  • Hybrid approach (GiBUU+SMM)
  • Applications
  • Benchmark: p+X@SIS/GSI (spallation reactions), X+X@SIS/GSI, (ALADIN)
  • X+X@2AGeV (HypHI), p+X@50GeV, X+X@20AGeV (J-PARC)
  • Final remarks

Many thanks to GiBUU-group

slide2

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…)
relativistic hypernuclei

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 from BB->BYK (3-body PS)
  • 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
slide4

(http://theorie.physik.uni-giessen.de/GiBUU)

  • Asymptotic equilibrated stage
  • Fission/spallation, evaporation, multifragmentation… (with increasing excitation)
  • Statistical determination of partial decay widths  Monte-Carlo method
  • (basic method similar to numerical treatment of collisions in transport approaches)

j,e

E*

Ai,Zi

E*-e

Ad,Zd

Ad+n

Ai

Theoretical description (pre-equilibrium dynamics, statistical decay)…

  • Initial non-equilibrium stage
  • Relativistic transport equation of Boltzmann-type
  • Giessen-Boltzmann-Uehling-Uhlenbeck (GiBUU)

Q.Li, J.Q. Wu, C.M. Ko, Phys. Rev. C39 (1989) 849

B. Blättel, V. Koch, U. Mosel, Rep. Prog. Phys. 56 (1993) 1

SMM code: Bondorf, Botvina & Mishustin, PR257(´95) 133

slide5

Total energy (Etot=∫dxT00) of a „source“  Excitation energy: Eexc=Etot-Ebind, of a „source“

  • local Pressures (Plong(x)=Tzz,Ptr(x)=Txx,yy)  Anisotropy ratios Qc (equilibration)

Theoretical description (hybrid GiBUU+SMM approach)…

slide6

Dynamical aspects in p+X and X+X reactions (properties of „fragmenting source“)…

  • Definition of residual nucleus: r>rsat/100.
  • Non-Equilibrium dynamics within GiBUU until system(s) approach local equilibrium at t=tf
  • Determination of A,Z and Eexc at time tf, and then apply SMM

p+Au@0.8GeV

Phys. Lett. B 663, 197 (2008)

slide7

Benchmark-I: p+X reactions (global characteristics)…

Exp. data:

J. Benlliure et al., Nucl. Phys. A683 (2001) 513.

F. Rejmund et al., Nucl. Phys. A683 (2001) 540

Charge distribution…

Mass distribution…

Phys. Lett. B 663, 197 (2008)

slide8

Benchmark-I: p+X reactions (details)…

Exp. data:

J. Benlliure et al., Nucl. Phys. A683 (2001) 513.

F. Rejmund et al., Nucl. Phys. A683 (2001) 540

Phys. Lett. B 663, 197 (2008)

slide9

Pre-Equilibrium (BUU): high-energy n-emission, QE-pick

  • Asymptotic equilibreated state (SMM): Statistical decay of excited source
  • Final Result: Hybrid GiBUU+SMM

Benchmark-I: p+208Pb@0.8GeV reactions (more details)…

data: S. Leray et al., PRC65,044621

neutrons

slide10

Dynamical aspects in p+p and 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

submitted (2008)

slide12

Heavy System

Light System

Formation mechanism of spectator-hypernuclei …(X+X@3AGeV)

  • Hyperons formed from high- phase(pB->YK,BB->BYK+PYTHIA) rescattering with „spectator“-particles
  • captured by cold „spectator“-clusters with high probability, e.g. 4,6He
  •  In collisions of heavy nuclei (Au) difficult separation from pion-background (fireball)
  •  Possible in collisions of light systems (Ca+Ca,C+C) with minor problems of pion-background (Fireball)
slide13

Hypernuclei from spectator fragmentation…(HypHI, 12C+12C@2AGeV)

Formation of hypernuclei from spectator fragmentation via coalescence

(condition: Y inside radius of fragmenting source+momentum coalescence)

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

submitted (2008)

slide14

Hypernuclei from high energy proton-induced reactions…(J-PARC, p+12C@50GeV)

submitted (2008)

Two sources (residual target+moving source)

Stable conditions after resonance decay

Most of hyperons created & rescatter inside moving source

final remarks outlook
Final remarks & Outlook…
  • Fragmentation in reactions within “hybrid” GiBUU+SMM
  •  BUU: non-equilibrium dynamics, info on onset of equilibration & instabilities
  •  Ground state stability important in extracting Ex
  •  SMM(Botvina/Mishustin): statistical decay of excited configuration
  • Fragmentation in proton-induced reactions & HIC
  •  GiBUU+SMM combined approach for fragmentation reactions
  •  reasonable description of a wide selection of exp. data
  • First transport predictions for future HypHI-project at GSI
  •  Light hyperfragment production from spectators with high probability
  • (however, coalescence picture too simple…)
  • Future/under progress developments
  •  Better description for strangeness sector of mean-field (in progress)
  •  Hyperfragment description more consistent:
  • GiBUU+HypSMM: would be an important extension for HypHI

A.S. Botvina, J. Pochodzalla, Phys. Rev. C76 (2007) 024909.

slide19

Transport equations of Boltzmann-type, very old story…

  • 1. Primer L. Boltzmann, Wien. Ber. 66 (1872) 275
  • 2. Primer…L. Nordheim, Proc. R. Soc. London A119 (1928) 689
  • E.A. Uehling, G.E. Uhlenbeck, Phys. Rev. 43 (1933) 552
  • Theoretical background
  • Non-Relativistic kinetic theory
  • L.P. Kadanoff, G. Baym, „Quantum Statistical Mechanics“ (Benjamin, N.Y. 1962)
  • Relativistic kinetic theory
  • S.R. de Groot, W.A. van Leeuwen, C.G. van Weert
  • „Relativistic kinetic theory“ (North Holland, Amsterdam, 1980)
  • Modern Relativistic Quantum Transport Theory
  • W. Botermans, R. Malfliet, Phys. Rep. 198 (1990) 115 (difficult to understand…)
  • First applications to HIC…
  • P. Danielewicz, Ann. Phys. 152 (1984) 239 & 305
  • G.F. Bertsch, S. Das Gupta, Phys. Rep. 160 (1988) 189
  • First relativistic applications to HIC…
  • Giessen-group (PhD-Thesis of B. Blättel, V. Koch & U. Mosel/W. Cassing ~1990)
  • B. Blättel, V. Koch, U. Mosel, Rep. Prog. Phys. 56 (1993) 1

Q.Li, J.Q. Wu, C.M. Ko, Phys. Rev. C39 (1989) 849

spectator matter properties buu
Spectator matter properties (BUU)…

Nice stable conditions…

…before instability sets in

  • Spectator very well suited for studies on fragments & hyperfragments