Michela D'AgostinoBologna UniversityINFN-Bologna (Italy) Eurisol and the nuclear EOS: experimental challenges Keyword from the 2003 Eurisol report: Isospin  Level density parameter dependence on (N,Z)  Liquid gas phase transition  Isospin effects and symmetry term of the EOS  Isospin effects in semi-peripheral Heavy-Ion reactions: symmetry term of the EOS Keyword from the 2003 Eurisol report: Isospin  Level density parameter dependence on (N,Z)  Liquid gas phase transition  Isospin effects and symmetry term of the EOS  Isospin effects in semi-peripheral Heavy-Ion reactions: symmetry term of the EOS Thermodynamics of a single source Dynamics of many-sources 1. 1.Are we ready to do this? 2. 2.What do we need to improve? It depends on the approximation we can accept

Heavy Ion collisions ~100 fm/c DETECTOR ~20 fm/c ( sec) ~100 ÷ 1000 fm/c ~10 14 fm/c Vacuum (10 -6 mb) Expansion γ emission Freeze-out configuration

124Sn+ 124Sn, E/A = 50 MeV/A b = 6 fm Freeze-out configuration 80 fm/c (2.4x sec) 180 fm/c (5.4x sec) DETECTOR Secondary decays ~÷1000 fm/c ~10 14 fm/c In event by event measurements statistical, multidimensional analyses allow a centrality sorting

H.I. collisions: 1-st generation 4π devices The decaying system can be identified and its calorimetric excitation energy results from the energy balance: Z i, k i, θ i, φ i are measured for almost all charged products, event by event, with high energy resolution (few %) and low energy thresholds (gas detectors) Statistical multidimensional analyses performed on global (event) observables allow to sort the events in classes of centrality. Fragments and particles are detected at ~10 14 fm/c, as they were at 10 3 fm/c, since the propagation in vacuum does not allow further interactions with matter. m i are measured only for light products neutrons and γ are not detected

Sorting the events: multidimensional analysis Central collisions: one source Multics-NPA724 (2003) 329 Filtered CMD model E. Geraci et al.,NPA732(2004)173,NPA734 (2004)524 Z>8 open circles >18 full points >28 open squares >38 full squares >48 open triangles >58 full triangles >68 open crosses MulticsNPA734(2004)487 V beam AZ Z,A for light Ions 124 Sn+ 64 Ni 35MeV/A Peripheral collisions: many sources Chimera data

1-st generation 4π devices & stable beams (V.Viola, R.Bougault-WCI-2005 TexasA&M) For all multifragmentation experiments, the region in which there is a dramatic change in reaction observables corresponds to E*/A = 5 +/-1 A.MeV Within a phase-transition scenario, this value represents the transition energy. Multics-NPA724 (2003) 329 Central collisions The current state of nuclear calorimetry permits determination of the E*/A of the fragmenting source to an accuracy of about 20%. Nearly all experiments can be made self-consistent within this range Multics: Central from Z 0 =85 to Z 0 =100 (lines) Multics: Au peripheral Z 0 =79 (symbols) Isis: π+Au 8 GeV/c NPA734(2004)487 Fasa: p,α+Au 4-14 GeV NPA709(2002)392 Z -2.1

J. Pochodzalla et al, PRL 75, 1040 (1995) For the caloric curve one needs to measure: Heavy residue (or QP) Slopes of 1-st chance l.c.p. energy spectra Isotopes (for double ratios) Temperature and caloric curve R. Wada et al., PRC 39, 497 (1989) N.Le Neindre et al, NIM A490 (2002) 251 Sequential feeding?

T from double ratios: Y(He 3 )/Y(He 4 ) Y(Li 6 )/Y(Li 7 ) V 1 =V 2 Isotope analysis

Symmetry energy and free nucleon densities E. Geraci, et al., Nucl. Phys. A 732 (2004) 173, Nucl.Phys. A734 (2004) 524  = 0.44 ± 0.01 Symmetry Energy~18-20 MeV 112,124 Sn+ 58,64 Ni 35 AMeV central collisions CHIMERA-REVERSE Experiment

Δ(Z/A)² D.Shetty et al., P. R.C 70 (2004) E.Geraci et al.,NPA732(2004) A.Botvina et al., PRC65(2002): Extraction of symmetry energy Asy-soft Asy-stiff Sequential feeding?

Experiments with n-rich/poor systems 32 S+ 58,64 Ni 14.5 AMeV 3-IMF events Before drawing conclusions on temperature, densities:   Isotope emission time scales have to be checked through correlation functions nucl-ex Observed 35 resonances, from He 4 (d+d) to Ne 20 (a+O 16 ) A rough calculation of “feeding correction” through correlation functions suggests an increase of T by 0.5 MeV for few % of decrease in the He 4 yield

J.B. Natowitz et al., PRC 65, (2002) N=Z J.Besprosvany and S.Levit - PLB 217 (1989) 1 Al-Quraishi PRC63,065803(2001) 114,145 Xe + 40,48 Ca E beam = A.MeV ε * = 3-7 A.MeV Level density (N,Z)

Position-sensitive hodoscope Pochodzalla et al., PRC35 (1987)1695 t-α correlation function (Li 7 *) m=multiplicity, N=number of detectors ε (m) = ε(1) m P(double)=(m-1)/(2N) A reasonable compromise is P(double)<5% For m=3 N=10 Resonance spectroscopy

Why many-body correlations? R.J. Charity et al., PRC Ni+ 100 Mo 11 A.MeV α-particles α-αα-α Δθ≈ 0.6 o  high granularity but in a limited angular coverage & not HR full identification

Neck emission in semi-peripheral collisions 58 Ni Sn at 35AMeV CHIMERA MC with only statistical evaporation QT QP filtered

- -Midvelocity LCP and fragments seem to be compatible with two sources, one “prompt”, the other like a “surface component”. This can be the evolution of the fast oriented fission for the most asymmetric splits See: Di Toro et al. Prog.Part.Nucl.Phys 53(2004),81 -- A.Chernomoretz et al. PRC 65(2002) Midvelocity Emissions: which origin? S.Piantelli et al. Phys.Rev.Lett.88(2002), A.Mangiarotti et al. Phys.Rev.Lett93(2004)232701

Isospin effects: strange ‘chemical’ behaviour for midvelocity particles Statistical Evaporation -N/Z for hydrogen is in good agreement with statistical codes Only protons N/Z=0 Only deuterons N/Z=1 38AMeV Preliminary S.Piantelli et al. (in preparation) TKEL N/Z For Midvel emission we have a large neutron enrichment. Multifragmentation? Isospin Distillation? THE HYDROGEN CASE

Neck emission in semi-peripheral collisions

Thermodynamics of finite systems: phase transition We can back-trace from data the average volume of the system (Coulomb trajectories) E*= E config + E kin E*= E coul (V)+Q v + E int (T)+E tr (T) Events sorted as a function of E* (calorimetry) the temperature T under the constraint of energy conservation Multics-Nucl.Phys.A699(2002)795 =(3/2) T+ T 2

Microcanonical heat capacity from fluctuations Ph.Chomaz, F.Gulminelli, NPA 647(1999) 153 The system being thermodynamically characterized: Multics-PLB473 (2000) 219;NPA699 (2002) 795;NPA734 (2004) 512; NPA749(2005) 55 Microcanonical fluctuations larger than the canonical expectation? Then 1-st order phase transition C kin /C = 1-  2 kin /  2 can where:  2 can =T 2 C kin =T 2 d /dT

Heat capacity from fluctuations Grey area: peripheral collisions Points: central collisions: Indra: NPA699(2002)795 Au+C Au+Cu Au+Au Multics: PLB473 (2000) 219 NPA699 (2002) 795 NPA734 (2004) 512 NPA749(2005) 55 E*/A 0 (AMeV) + new analyses by

Average values and variances If we only use average and uncorrelated information on: freeze-out multiplicity of neutrons, Z=1,2 and IMFs sequential feeding excitation energy of primary fragments N/Z of final products We see that one half of the game is played by missing correlations!!!!!! Nucl.Phys.A699(2002)795 SMM events

3-d Spinodal region M.Colonna et al. PRL 88(2002) Instability growth time 100 fm/c (dashed/orange) 50 fm/c (dotted/red) More asymmetric systems are less unstable

Do we need to improve the detection for the “isospin” physics? For all the measured reactions (high geometrical coverage, high energy resolution), event by event : Z,A,E,θ,φ of the Heavy residue (QP&QT(?) for peripheral collisions) Z,A,E,θ,φ for fragments(*) and l.c.p. (high ε*) correlations among charged products (*) is it enough mass for Z<=20? At least on the average, for each reaction (sequential experiments) Neutron multiplicity & energy (Gammas??)

Mass distribution of Ge (Z=32) isotopes 86 Kr (25 MeV/u) + 64 Recoil separator Texas A&M G.A. Souliotis NN2003(Moscow) Heavy fragment mass&charge identification

1. 1. Z, A, and E (low energy thresholds) 2. 2.Granularity (for resonance spectroscopy) 3. 3.Neutron detection (E n, M n ), at least on the average 4. 4.Cheap, flexible electronics 5. 5.Easy transportability 6. 6.Improvement of detector calibration (neural networks?) Future detector needs Chimera: Pulse shape gives Z identification with ~ 4 MeV/A energy threshold for particles stopped in Si detector Nuclex: Reverse mounting of the Si detector & Digital Pulse Shape give Z identification with ~ 2.5 MeV/A energy threshold for particles stopped in Si detector

FAZIA: Four π A-Z Indentification Array ~6000 telescopes: Si-ntd/Si-ntd/CsI possibility of coupling with other detectors like spectrometer, gas chamber, neutron detectors ~1000 hits/s maximum multiplicity ~150/event complete Z identification and A up to ~30 digital electronics for pulse-shape discrimination half forward part

FAZIA: Four π A-Z Indentification Array