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Fragment formation in low energy proton-induced reactions within a hybrid BUU+SMM approach

Fragment formation in low energy proton-induced reactions within a hybrid BUU+SMM approach. Th. Gaitanos, H. Lenske, U. Mosel. Introduction Theoretical description Non-equlibrium stage (GiBUU) Asymptotic equilibrium stage (SMM) Hybrid approach (GiBUU+SMM) Applications

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Fragment formation in low energy proton-induced reactions within a hybrid BUU+SMM approach

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  1. Fragment formation in low energy proton-induced reactions within a hybrid BUU+SMM approach Th. Gaitanos, H. Lenske, U. Mosel • Introduction • Theoretical description • Non-equlibrium stage (GiBUU) • Asymptotic equilibrium stage (SMM) • Hybrid approach (GiBUU+SMM) • Applications • Benchmark p+X@SIS/GSI energies • Final remarks

  2. Non-(pre-)equilibrium first phase Asymptotic final state Highly excited system Dynamical transport (BUU, QMD, INC) Equilibrated source with small excitation Statistical multifragmentation models „Hybrid“ models (BUU+SMM) Introduction… • Spallation reactions („small“ excitation of residual nucleus resp. to its ground state) • useful tool to theoretically study/test long-time scales of fragmentation process • Applications • Study of hypernuclei (2nd talk): HIC@SIS (HypHI) • In future: PANDA (pbar+X), J-PARC (p+X@50GeV, X+X@20AGeV) Theor. description of Low energy hadron-induced reactions

  3. 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… • Initial non-equilibrium stage • Relativistic transport equation of Boltzmann-type • Giessen-Boltzmann-Uehling-Uhlenbeck (GiBUU) (http://theorie.physik.uni-giessen.de/GiBUU) SMM code: Botvina & Mishustin, PR257(´95) 133

  4. Benchmark: p+Au@0.8GeV (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 e-Print: arXiv: 0712.3292 (almost accepted…)

  5. Benchmark: p+Au@0.8GeV (global characteristics)… Charge distribution… Mass distribution… e-Print: arXiv: 0712.3292 (almost accepted…) Data: F. Rejmund et. al., NPA683(´01) 540 J. Benlliure et. al., NPA683(´01) 513

  6. Benchmark: p+X reactions (details)… e-Print: arXiv: 0712.3292 (almost accepted…) Data: F. Rejmund et. al., NPA683(´01) 540 J. Benlliure et. al., NPA683(´01) 513

  7. Final remarks & Outlook… • Low-energy proton-induced reactions •  Residual system under stable conditions • no compression/expansion effects, no radial flow effects •  Wide selection of experimental data •  Useful tool to study transport models including fragmentation • Hybrid approach (GiBUU+SMM) •  Initial stage: Stable ground state •  pre-equilibrium dynamics: relativistic GiBUU •  asymptotic equilibrated stage: statistical decay by means of SMM • Comparison with a wide selection of exp. data •  Global characteristics and details fairly well reproduced • Future/under progress developments •  Gradient terms in meson field equations (A.Larionov) •  Extended for iso-vector degrees of freedom (r-meson) •  More consistent treatment of ground state (RTF)

  8. Important in determing the source • No spurious particle emission! Ground state in BUU: Stability… • Important in calculating Eexc • Energy must be conserved! Improved model for ground state simulations in BUU B. Steimüller, O. Buss, U. Mosel, poster session, HK34.87

  9. Dynamical aspects in p+X reactions… • Definition of residual nucleus: r<rsat/100. Combination: BUU+SMM (hybrid model)… • Non-Equilibrium dynamics within BUU until system(s) approach local equilibrium at t=tf • Determination of A,Z and Eexc at time tf, and then apply SMM

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