1. Fusion-Incomplete Fusion Dissipative binary processes
Sez.-CT
GDR pre-equilibrium emission 40Ca+48Ca,46Ti at 25 MeV/A
S.Tudisco EPL 58 (5), 811(2003)
M.Papa et al, PRC 68., (2003)
F.Amorini et al PRC 69, (2004)
M.Papa et al EPJ A4 (1999) 69
F.Amorini et al PRC 58 (1998) 98
Fusion-Incomplete Fusion
Dissipative binary processes
Extra yield at 10 MeV

2. Dissipative binary processes study of kinematical coincidence
GDR pre-equilibrium emission 40Ca+48Ca,46Ti at 10 MeV/A
M.Papa et al, submitted to PRC
Dissipative binary processes
study of kinematical coincidence

3. Z=14-22 Elab<160 MeV 40Ca+46Ti 40Ca+46Ti 40Ca+48Ca γ-2f γ-1f
•Accurate selection of events for which, different quantities measured
for the two systems look very similar.

4. CoMD calculations
TKEL-angular and charge distrib.
b-window→ pre-eq γ Yield
Calculated dynamical pre-eq yield able
to explain the extra-yield

5. If Y=0 NO coherent contribution
How we can generate the coherent
contribution?
A simple picture the “Molecular Dipole”
Sez.-CT
The average ensemble in an harmonic mean field
The initial conditions for the GDR mode
At the contact D1≈D2 ≈0 n p
N1/Z1≠N2/Z2 if
M.Papa et al EPJ A 4
69 (1999) and ref.there in
If Y=0 NO coherent contribution

6. Statistical models Mean field approach Sez.-CT Incoherent contribution
Collective
Microscopic incoherent
Coherent contribution
(ensemble average)
Statistical models
Mean field approach
Fully N-body dynamical approach for 1000 fm/c an unified description
M.Papa et al, PRC 68., (2003)

7. Υ-ray average multiplicity in semi-classical approximation
Sez.-CT
The Larmor formula
Fourier Transform
Formal analogy with scattering
amplitude theory- quite general way to define statistical
processes.

8. b=0 fm E/A 25 MeV
Sez.-CT
Langevin prediction for the total system
Prediction in the loc. Time
equil. hypothesis
Prediction according to a
full CoMD approach
g~12
M.Papa et al, PRC 68(2003)

9. We have also high energy bremsstrahlung contribution
Sez.-CT
We have to study the local time
spectral properties of the  yield
We need to define T at long time
We need to separate the
incoherent Microscopic contribution

10. Multifragmentation of the hot source
Sez.-CT
High energy results
Multifragmentation of the hot
source

11. Coherent contribution
50 MeV/A b=0 fm
Sez.-CT
M.Papa et al, PRC 68(2003)  
 obtained from the fit procedure
Very small
Coherent contribution or

12. Something is changed in the fundamental
properties of the formed hot sources….
Degree of collectivity-Degree of coherence as function of t

13. A new observables related to the properties of the dipolar γ-ray emission in different reaction mechanisms have been measured.
- Φch represents the ratio between the average and fluctuating dynamics.
For N-body approaches able to evaluate the two contributions in a self consistent way, this parameter should be rather robust with respect some model ansatz: semi-classical approximation, occupation numbers…….
- On the other hand and we can expect that Φch can depend
on the dynamics (Forces) governing the equilibration
Process.
From the experiments
Фch(12MeV)=0.6±0.15
10 MeV/A Binary. proc.
Фch(10 MeV)=0.3±0.07
25 MeV/A Inc. fusion.proc.

14. 40Ca + 48Ca Central Collisions
Collectivity and Coherence for the total system
limiting energy for the collective motion-GDR quenching
M.Papa et al, PRC 68(2003) ,
Black: collectivity long times
rather smooth behaviour
c(0,tm)
c(0,tf)
ch(0,tf)
40Ca + 48Ca Central Collisions
Red: collectivity short times, it contains the
ambiguity related
to the experimental
selections of 1
equilibrated source
*10
Green:Coherence, high sensitivity related to the natural time selection performed by the dynamics through memory effects.

15. γ-Pre-equilibrium effects and “Isospin-Equlibration”
non diffusive mechanism-”quasy resonant mechanism”
M.Papa et al Sub. to PRC
Invariant with respect to
secondary statistical emission
processes

16. Conclusive remarks degree of collectivity φc)
Sez.-CT
An unified description of the pre-equilibrium phenomenon (fluctuating-average dynamics) has been obtained in a fully dynamical approach by means of ComD calculations.
The fluctuations predicted by the model are in agreement with Cascade calculations at 25 MeV/A and for long time by using g≈12. The fluctuations on the collective motion show marked non-equilibrium features at short time. This effect is able to describe the GDR quenching.
The degree of coherence φch rapidly change when the multifragmentation processes set in. (much more than the
degree of collectivity φc)
3. In the explored incident energy range, (8-25 MeV/A) the dynamical pre-equilibrium extra-yield seems to be strictly related to the isospin equilibration process throgh a “quasy-resonant” mechanism.