1. Fragment-fragment correlations
Access to time-scales of fragment emission and densities at freeze-out
Mechanisms of fragment emission
Phase transition and low freeze-out density?
Simultaneous multifragment emission
short t < 100 fm/c ~ growth of density fluctuations (bulk instabilities)
Sequential evolutionary emission?
Evolutionary emission? EES predictions
larger t values. t ≥ 300 fm/c

2. Qrel correlations Nautilus Kr+Au:
MIMF>2: t ≈ A.MeV – t ≈ A.MeV
Louvel et al., PLB 320 (1994) 221
Central: «prompt and simultaneous fragment emission» 
Lopez et al., PLB 315 (1993) 34
FASA 8.1 GeV: t ≤ 70 fm/c - VFO = (5  1) Vo
V.K. Rodionov et al., NPA 700 (2002) 457
V.A.Karnaukhov et al.

3. IMF-HR vs IMF-IMF correlation functions
F-F and HR-IMF events vs Multigramentation events
IMF-HR correlations:
tIMF-HR ≈ fm/c
rotating binary decay
IMF-IMF correlations: time scales for multifragment emission
tIMF-IMF ≈ fm/c
No significant change in time scales: sequential IMF emission
Mfrag>1 => not enough to select multifragmentation events
R. Trockel et al., PRL59, 2844 (1987)

4. IMF timescales
Miniball data vs 2-Body Coulomb FSI, Y.D. Kim et al., PRL 67 (1991) 14
all
3-Body Coulomb trajectories slightly modify extracted times, and are important to investigate emitter sizes
Y.D. Kim et al., PRC45 (1992) 387
T. Glassmacher et al., PRC50 (1994) 952
t ≈ fm/c: Shorter than seq. evaporation

5. Apparent evolutionary multifragmentation
Central Kr A.MeV (b < 0.2 bmax)
Apparent emission times tIMF depend on fragment velocities
Apparent evolutionary fragment emission mechanisms (EES predictions)
C-Be time ordering measurement relative velocity
Simultaneous emission +
thermal/radial flow
can explain this effect
Miniball data, E. Cornell et al., PRL75 (1995) 1475
E. Cornell et al., PRL77 (1996) 4508
Similar conclusions in G. Wang et al., PRC 60 (1999)
for central A.MeV (Isis): r/r0 = 1/4-1/3 – t  50 fm/c

6. tIMF vs incident energy: onset of simultaneous multifragmentation
Central Kr+Nb (b < 0.3 bmax)
35 AMeV
45 AMeV
55 AMeV
65 AMeV
75 AMeV
Onset of simultaneous multifragmentation
(bulk instabilities)
Beam Energy (A MeV)
500
400
300
200
100
tIMF (fm/c)
r0   tapp 
flow   tapp 
MSU 4p data, E. Bauge et al., PRL70 (1993) 3705

7. tIMF vs excitation energy: from surface to bulk emission in thermal multifragmentation
p-, p + A , 8.2, 9.2, 10.2 GeV/c
ISiS data, L. Beaulieu et al., PRL84 (2000) 5971
Thermally expanding and decaying source: tIMF decreases with increasing E*/A (assuming constant r=r0/3)
Transition from surface emission to bulk emission around E*/A≈4-5 MeV ?
Analysis: N-Body Coulomb trajectories
T. Glassmacher et al., PRC50 (1994) 952
R. Popescu et al., PRC58 (1998) 270

8. About the space-time ambiguity
A.MeV – Miniball data – b/bmax ≤ 0.2
D. Fox et al., PRC50 (1994) 2424
Koonin-Pratt
and 3-body Coulomb trajectory calculations
The space-time extension of the composite system at freeze-out decreases with increasing beam energy
Zres dependance

9. Summary What have we learnt from fragment-fragment
Vred and Qrel correlations?
With increasing beam or excitation energy, apparent IMF emission times decrease down to “simultaneous” emission
fission “simultaneous” bulk emission (multifragmentation)
≈1000 fm/c ≤100 fm/c
=> for multifragmentation : evolutionnary type of descriptions (EES) can hardly account for apparent timescales
The space-time extension of the emitting sources diminishies.
As the radial and thermal flows develops…
New correlation methods are needed to solve the space-time ambiguity, where flow should be taken into account when simulating N-body Coulomb trajectory in volume emissions. E* t
2 A.MeV
4 A.MeV
sequential
surface emission

10. Time sequence and time scale of neck fragmentation
124Sn + 64Ni 35 A MeV (ternary events PLF-IMF-TLF, Chimera data)
Prompt 1 2 3
fm/c
fm/c
fm/c
Results of BNV transport model for IMFs emission probability from neck region for different impact parameters (V. Baran et al. Nucl. Phys. A , 2004).
Ternary
Sequential binary