Charge Equilibration Dynamics: The Dynamical Dipole Competition of Dissipative Reaction Mechanisms Neck Fragmentation M.Di Toro, PI32 Collab.Meeting, Pisa 05 Isospin Dynamics in Dissipative Heavy Ion Collisions

Symmetry Energy E sym    MeV)     1230 Expansion around   Pressure & compressibility Asy-stiff Asy-soft Pressure gradient

Mean Field & Chemical Potentials 124 Sn “asymmetry”  = 0.2 symmetry part of the mean fieldneutron-proton chemical potentials neutron proton bulk neck

STOCHASTIC MEAN-FIELD TRANSPORT APPROACH VLASOV + COLLISION and PAULI CORRELATIONS FLUCTUATIONS Equilibrium in a phase space cell OK if tot. number of collisions Initial: any time FLUCT.-DISS. THEOREM gainloss Markov NPA 642 (1998)

D(t) : bremss. dipole radiation CN: stat. GDR Initial Dipole Pre-equilibrium Dipole Radiation Charge Equilibration Dynamics: Stochastic : Diffusion vs. Collective : Dipole Oscillations of the Di-nuclear System Fusion Dynamics - Fusion Dynamics (MassAsymmetry) - Anisotropy - Cooling on the way to Fusion

Pre-equilibrium dipole emission (1) Ca + 4 AMeV O + 4,8,14,20 AMeV O AMeV, Simenel et al., PRL86(2001) Baran et al., PRL87(2001) TDHF BNV Quantitative: abs. estimations

S32 + Mo100 (6 AMeV) S32 + Mo100 (9 AMeV) D(t) Dk(t) time(fm/c) Pre-equilibrium dipole emission (2) D.Pierroutsakou et al. (2005) M.Papa et al., AMeV Cooling in hot fusion ?

Fusion - Deep Inelastic Competition E= 30 AMeV, b=0.45 b max 46 Ar + 64 Ni (1.55) (1.29) n-rich 46 V + 64 Ge n-poor M. Colonna et al., PRC57 (1998) Asy-soft Asy-stiff Asy-soft Asy-stiff More fast proton emission

b=4fmb=6fm 124Sn+124Sn 50AMeV, semi-central STOCHASTIC MEAN-FIELD Freeze-out V.Baran et al. NPA 703 (2002) Time-scale matching: Instability growth vs Interaction time Rise and Fall: -with impact parameter - with beam energy Neck Fragmentation Mechanism

NECK FRAGMENTATION: COMPRESSIBILITY EFFECTS the role of volume instabilities K=380MEV soft stiff Central density evolution cube of 10fm side K=200MEV 124 Sn+ 64 Ni 35AMeV b=6fm V.Baran et al. NPA 730 (2004)

NECK FRAGMENTATION EVENTS free cross sectionshalf free cross sections up -early stage of fragment formation down- configurations close to freeze-out Nucleon-nucleon cross sections dependence P=N ternary /N total 124 Sn+ 64 Ni 112 Sn+ 58 Ni 124 Sn+ 64 Ni ; 35AMeV; b=6fm

DEVIATIONS FROM VIOLA SYSTEMATICS r - ratio of the observed PLF-IMF relative velocity to the corresponding Coulomb velocity; r1- the same ratio for the pair TLF-IMF The Neck - IMF is weakly correlated with both PLF and TLF Wilczynski-2 plot ! V.Baran, M.Colonna, M.Di Toro NPA 730 (2004)

REDUCED VELOCITY PLOTS: BNV V. Baran et al. Nucl. Phys A730 (2004) 329 Note: BNV model accounts only for the “prompt” component of IMF’s Chimera 124Sn+64Ni 35AMeV data, same E_loss selections

Gating the reduced plot for light IMFs:

NECK FRAGMENTATION: CM V z -V x CORRELATIONS PLF IMF TLF Large dispersion also along transversal, x, direction 124 Sn + 64 Ni 35 AMeV  <0  >0 Alignement + Centroid at Clear Dynamical Signatures !

Angular distributions: alignment characteristics  plane is the angle, projected into the reaction plane, between the direction defined by the relative velocity of the CM of the system PLF- IMF to TLF and the direction defined by the relative velocity of PLF to IMF Out-of-plane angular distributions for the “dynamical” (gate 1) and “statistical” (gate 2) components: these last are more concentrated in the reaction plane.

124 Sn+ 64 Ni 35AMeV asystiffasysoft 64 Ni 124 Sn superasystiff ISOSPIN COMPOSITION OF THE IMF’S PRODUCED IN NECK FRAGMENTATION: ASY-EOS EFFECT

N  = 0.95 Z=1 Z=3 Z=2 Z=5 Z=7 Z=6 Z=8 Z=4 Z=9 lnR 21 NECK ISOSCALING at 35 MeV/n (b=6,7,8fm) asysoft asystiff superasystiff  V. Baran, M. Colonna, M. Di Toro : NPA 370 (2004) 329

Z ln R 21  = N=2 N=3 N=8 N=7 N=6 N=5 N=4 NECK ISOSCALING at 35 MeV/n (b=6,7,8fm) asysoft asystiff superasystiff 

58Fe+58Fe vs. 58Ni+58Ni b=4fm 47AMeV: Freeze-out Asymmetry distributions Fe Ni Fe Ni White circles: asy-stiff Black circles: asy-soft Asy-soft: small isospin migration Fe: fast neutron emission Ni: fast proton emission R.Lionti et al., nucl-th/

Neck Fragments: N/Z – angle correlation FeFe vs NiNi b=4fm 47AMeV: 40% ternary - Isospin Migration for almost symmetric systems - Minimum N/Z around 90° : earlier formation? R.Lionti et al, nucl-th/

FeFe b=4fm 47AMeV: density contour plots fm/c PLF/TLF residues asymmetry (N-Z)/A System initial t=100fm/c(after pre-eq) freeze-out 58Fe+58Fe binary 1.19 ternary 58Ni+58Ni binary 1.12 ternary n-enrichment of Neck-Fragments even for symmetric systems! R.Lionti et al. nucl-th/