Ternary and quaternary reseparation of heavy colliding systems K. Siwek-Wilczyńska University of Warsaw for the CHIMERA Collaboration Bormio 2011

Charged Heavy Ion Mass and Energy Resolving Array (CHIMERA) Laboratori Nazionali del Sud, Catania Superconducting Cyclotron K = 800 197Au + 197Au, 15 & 23 MeV/nucleon Charged Heavy Ion Mass and Energy Resolving Array (CHIMERA) Target 1192 Si-CsI(Tl) telescopes in 4 geometry

The aim ==> to study the reaction mechanism of the collisions of very heavy nuclei in the energy range below the multifragmentation threshold (~ 30 MeV/nucleon) Light and medium heavy systems ► Fusion-evaporation or fission ► Deep inelastic collisions Very heavy systems ► Fusion ► Deep inelastic collisions (binary) ► Ternary separation into 3 large fragments (??) ► Reseparation into 4 large fragments (??) CN TLF PLF CN TLF PLF F1 F2 F4 F3 ??

Charge fragments Z  3 multiplicity ( LAB angles 2.60 to 860). 197Au + 197Au @ 15 MeV/nucleon Charge fragments Z  3 multiplicity ( LAB angles 2.60 to 860). analysis: events with 2, 3 and 4 fragments Counts 1 2 3 4 5 6 7 8 Multiplicity

Ternary events 197Au + 197Au Dalitz diagram Ai /(A1+A2+A3) A3 A1 A2 Complete events: 3 fragments + nucleons and ligth evaporated particles Selection of events: Z1, Z2, Z3 ≥ 3, Z4, Z5 ... ≤ 2 AP + AT − 70 ≤ A1 + A2 + A3 ≤ AP + AT |∑ plong(1,2,3)| > 0.8 po |∑ ptrans(1,2,3)| < 0.04 po Dalitz diagram A3 = TLF (Target-Like-Fragment) Most probable ternary events 0.38 ≤ ATLF/A ≤ 0.53 0.15 ≤ A1/A, A2/A ≤ 0.38 Two step process: 1. TLF* + PLF* TLF* → A1 + A2 PLF* → A1 + A2 Ai /(A1+A2+A3) A3 A1 A2

Events with 3 fragments F1 PLF* F2 Counts TLF Two-step process: Mass number Counts F1 F2 PLF* beam TLF Two-step process: 1. PLF* +TLF 2. PLF*→ F1 + F2

Ternary events: 197Au + 197Au → TLF + F1 + F2 EXPERIMENT THEORY Bez filtra F1 F2 PLF PLF TLF EXPERIMENT THEORY Quantum Molecular Dynamics (QMD, J. Łukasik)

197Au +197Au → TLF + PLF* → TLF + F1 + F2 SCHEME OF REACTION: 197Au +197Au → TLF + PLF* → TLF + F1 + F2 Counts 90 (deg) υ (deg)

TIME SCALE OF THE PLF* BREAK-UP Φ distribution: PLF* rotates about ΔΦ = 15o until it separates Time Δt corresponding to the rotation by ΔΦ: Δt = ΔΦ∙ I / J I – moment of inertia J – intrinsic spin of PLF* Counts -100 0 100 In-plane angle Φ (deg) Counts I and J estimated from the dynamical code HICOL assuming experimentally observed TKEL in the (primary) binary process TKEL  450 MeV Lmax = 1160 ħ, J = 75 ħ Hence, Δt  70-80 fm/c 200 600 1000 1400 Ekin(PLF*+TLF), MeV

Quaternary events 197Au +197Au → TLF* + PLF* F1 + F2 + F3 + F4 WITHOUT FILTER Quaternary events 197Au +197Au → TLF* + PLF* F1 + F2 + F3 + F4 PLF TLF WITH FILTER F2 F1 PLF F3 PLF F4 TLF TLF EXPERIMENT QMD SIMULASION

Determination of the impact parameter for binary, ternary and quaternary processes (deg) (deg) Ekin(PLF* + TLF*) - the total kinetic energy of the PLF*+TLF* system calculated as for a binary process. (deg)

Impact parameter localization deduced from model calculations

Summary SUMMARY A new reaction mechanism: the violent break-up into 3 or 4 large fragments was observed in semi-peripheral collisions of a very heavy system (Au+Au) at bombarding energies of 15 MeV/nukleon. In these processes all fragments move nearly collinearly in the center of mass system. The deviations from the collinearity allow to deduce the secondary break-up time (after binary reseparation) of the order of 70-80 fm/c (very short !) Existing theoretical models (BUU, BNV, QMD) are not able to reproduce experimental observations. Modifications are required (parameters of the EOS, Pauli blocking…). Localization of the observed reactions in the impact parameter space was determined. Our results suggest that the fast ternary and quaternary break-up reactions can be viewed as a natural extension of the binary DIC to the region of small impact parameters and very large inelasticity.

Phys. Rev. Lett. 101, 262701 (2008) Phys. Rev. C 81, 067604 (2010) I. Skwira-Chalot1, K. Siwek-Wilczyńska1, J. Wilczyński2, F. Amorini4, A. Anzalone4, L. Auditore10, V. Baran4, J. Brzychczyk8, G. Cardella3, S. Cavallaro4, M.B. Chatterjee5, M. Colonna4, E. De Filippo3, M. Di Toro4, W. Gawlikowicz11, A. Grzeszczuk7, P. Guazzoni6, S. Kowalski7, E. La Guidara4, G. Lanzano2, G. Lanzalone3, C. Maiolino4, Z. Majka8, N.G. Nicolis9, A. Pagano3, M. Papa3, E. Piasecki11,2, S. Pirrone3, R. Płaneta8, G. Politi3, F. Porto4, F. Rizzo4, P. Russotto4, K. Schmidt7, A. Sochocka8, Ł. Świderski2, A. Trifiro10, M. Trimarchi10, J.P. Wieleczko12, L. Zetta6, W. Zipper7 1 Institute of Experimental Physics, Warsaw University, Warsaw, Poland 2 A. Sołtan Institute for Nuclear Studies, Świerk/Warsaw, Poland 3 INFN, Sezione di Catania and Dipartimento di Fisica e Astronomia, Università di Catania, Italy 4 Laboratori Nazionali del Sud and Dipartimento di Fisica e Astronomia, 5 Saha Institute of Nuclear Physics, Kolkata, India 6 INFN, Sezione di Milano and Dipartimento di Fisica, Università di Milano, Italy 7 Institute of Physics, University of Silesia, Katowice, Poland 8 M. Smoluchowski Institute of Physics, Jagellonian University, Cracow, Poland 9 Departament of Physics, University of Ioannina, Ioannina, Greece 10 INFN, Gruppo Collegato di Messina and Dipartimento di Fisica, Università di Messina, Italy 11 Heavy Ion Laboratory, Warsaw University, Warsaw, Poland 12 GANIL, CEA, IN2P3-CNRS, Caen, France