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

2. 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

3. 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 ??

4. 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
Multiplicity

5. 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

6. 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

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

8. 197Au +197Au → TLF + PLF* → TLF + F1 + F2
SCHEME OF REACTION:
197Au +197Au → TLF + PLF* → TLF + F1 + F2
Counts
90 (deg)
υ (deg)

9. 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
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  fm/c
Ekin(PLF*+TLF), MeV

10. 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

11. 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)

12. Impact parameter localization deduced from model calculations

13. 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 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.

14. 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