laboratory for nuclear physics division of experimental physics

Laboratory for Nuclear PhysicsLaboratory for Nuclear Physics Division of Experimental Physics Division of Experimental Physics RRuđeruđer Bošković Bošković Institute, Zagreb, CroatiaInstitute, Zagreb, Croatia

Zoran Basrak

11th International Conference on Nucleus-Nucleus Collisions May 28 – June 1st, 2011, San Antonio, TX–USA

Philippe Eudes, Maja Zorić, and François SébilleIn collaboration withIn collaboration with

Landau-Vlasov simulationTransport equation of the Boltzmann type

H = T+U, U = Vnucl+VCoul ,

Vnucl – Gogny G1-D1 non-local potential K=228 MeV, m*/m=0.67

f = f(r,p;t) - distribution function

Collision termPhenomenological, isotropic σ = σ(E, iso) [Chen et al.]

An approach adequate for bulk (one-body) properties of nuclear dynamics, in particular for an early and compact reaction phase

Dynamical emission component

P. E

u des

, Z. B

asra

k an

d F

. Seb

i lle

, Ph y

s. R

ev. C

56 (

199 7

) 20

0 3.Landau-Vlasov model

simulation

Ar ( 65 MeV / u ) Al

Ar ( 65 MeV / u ) Al A similar two-stages processin 1A GeV range by EOS CollJ.A. Hauger et al. PRL 77 (1996) 235.

A similar conclusion valid forany reaction below 100A MeV

A HI collision is decisively governed by the early and compact reaction stage.

In violent collisions during this compactreaction phase an important mass andenergy is evacuated from system.

An early energy transformation should should be studied in more detailbe studied in more detail.

Early reaction phase

Early energy transformation

Etot = Ecollect + Eintrin Eintrin = Eexcit + Epotent

Eexcit EExx//AA

Decompression followed by abundant emission and fast system cooling.

Asys = ~60 - ~400 nucl

Aproj:Atarg = 1:1 – 1:5

System Incident energy (MeV/u)

40Ar+27Al 25, 41, 53, 65, 77, 99

36Ar+58Ni 52, 74, 95

40Ar+107Ag 20, 30, 40, 45, 50, 75, 100

40Ar+197Au 50, 75, 100

36Ar+36Ar 32, 40, 52, 74

58Ni+58Ni 52, 74, 90

12OXe+129Sn 25, 32, 39, 45, 50, 75, 100

197Au+197Au 20, 30, 40, 60, 80, 100

Evolution of excitation energy

– Regular rise & fall with time at each EIN

– Width & height regularlybehave as a f(EIN)

Evolution of excitation energy

– Regular rise & fall with time at each EIN

– Width & height regularlybehave as a f(EIN)

– Maxima reflect the totalenergy deposited inthe reaction system

Excitation energy maxima

Eproj

Aproj

Eavail = Atarg Aproj

(Atarg+Aproj)2

Ex as a fraction of EAVAIL

– Fraction is almost constant over a wide energy range

– Large variety of systems

Experimental excitation energy In HIR excitation energy Ex is not directly

accessible.

Calorimetry. Various corrections for issues which are not under control. Often one resorts to theoretical predictions.

To obtain Ex/A besides the total excitation energy also the mass of the primary emission source has to be estimated.

One must add a problem of selecting events according to reaction centrality.

One cannot expect a most direct compa-One cannot expect a most direct compa- rizon simulation – experiment rizon simulation – experiment

All available data onEx/A in central HIcollisions in the last20 years

Experimental excitation energy

Experimental excitation energyAll available data onEx/A in central HIcollisions in the last20 years– Strong spread of the data points– Connected data points of the same measurement– Close to linear dependence on EIN

Data for EIN > 100A MeV

W. R

eisd

orf

et a

l ., N

ucl .

Ph y

s. A

848

(20 1

0) 3

66.

– Radial flow of light reaction products deduced on two manners– Some correction relative to FOPI PHASE 1 but still a linear function of EIN

Radial flow deduced by blast model.

Remaining energy is taken as thermal.

W. R

eisd

orf

et a

l ., N

ucl .

Ph y

s. A

612

(199

7) 4

93.

All available data onEx/A in central HIcollisions in the last20 years– Strong spread of the data points– Connected data points of the same measurement– Close to linear dependence on EIN

Experimental excitation energy

Experimental excitation energyAll available data onEx/A in central HIcollisions in the last20 years– Strong spread of the data points– Connected data points of the same measurement– Close to linear dependence on EIN

– Data within 35 % and 95 % of EAVAIL


– The same system for the central collisions and the same EIN displays different features


– Different leading assumption used in various analysis


D. D

ore

et a

l. (I

ND

RA

Col

labo

rati

on),

Ph y

s. L

ett.

B49

1 (2

000)

15.Ar (95A MeV) + Ni INDRA experiment

analyzed in the 3 sources assumption

QP emission in BDCs

QP mass

QP excitation

experiment

3 sources analyses

Proton reduced rapidity distribution

Reaction dominantly of binary nature witha strong mid-rapidity contribution.


– Different leading assumption used in various analysis

– Group data by the approach used


Neglected dynamical emission (?)

Pure kinematical considerations

Accounted dynamical emission

Added FOPI thermal energy

Summary “Hard” NN collisions play an importantNN collisions play an important role role in the dynamics of HIR already @@ EEFermiFermi

Maxima of excitationexcitation Ex (heat) gene- rated in a collision display linearitylinearity with incident energy EEININ

Ex represents a constant fraction ofconstant fraction of available system energy EEAVAILAVAIL

Some of experimental dataexperimental data (excluding the pre-equilibrium dynamical contribution ?) display a tendency of similar similar constancyconstancy with EIN

Laboratory for Nuclear PhysicsLaboratory for Nuclear Physics Division of Experimental Physics Division of Experimental Physics RRuđeruđer Bošković Bošković Institute, Zagreb, CroatiaInstitute, Zagreb, Croatia

Zoran Basrak

11th International Conference on Nucleus-Nucleus Collisions May 28 – June 1st, 2011, San Antonio, TX–USA

Philippe Eudes, Maja Zorić, and François SébilleIn collaboration withIn collaboration with

Backup slides

Central collisions

30 fm/c = 1∙10-21 s

Ex≈EAVAIL

full stopping

Ein = 10A MeV

At EFermi (≈ 35A MeV)“hard” NN collisions

Ein = 35A MeV

129Xe + 120Sn

BDC > 95 % REAC

≈ 5 % σREAC

b = 3 fm ≈ 0.2 bmax

Ein = 50A MeV

Ein = 125A MeV

Mid-rapidity emission in BDCs

≈ pre-scission emissionMid-rapidity emission

max. compression

max. compression

local equilibration

local equilibration

Co

nfi

gu

rati

on

sp

ace

Imp

uls

e sp

ace

pre-scission post-scission

P. E

u des

, Z. B

asra

k an

d F

. Seb

i lle

, Ph y

s. R

ev. C

56 (

199 7

) 20

0 3.

Central collisions Above Coulomb barrier an adiabatic

system rearrangement with full stopping and full E dissipation; fusion process EDISSIP = EAVAIL

Increasing E: incomplete fusion EDISSIP < EAVAIL

From about the Fermi energy EFermi BDCBDC > 95 % REAC irrespectively of

- event centrality - system size - system asymmetry

Increasing contribution of hard NN collisions

F. H

adda

d e t

al . ,

Ph y

s. R

ev. C

60 (

199 9

) 03

1 603

.

Z dynam emiss

Z targ + Z proj

= 100

Dynamical emission component

Dem (%) =

SystemIncident

energy (MeV/u)

40Ar+27Al 41, 65

40Ar+107Ag 50, 75, 100

107Ag+40Ar 50

36Ar+58Ni 52, 74, 95

12OXe+129Sn 50, 75, 100

Excitation energy maxima

Eproj

Aproj

Eavail = Atarg Aproj

(Atarg+Aproj)2


– Fraction almost constantover a wide energy range

– For symmetric systemsbreak below EFermi

– Large variety of systems

Fraction for experimental Ex

Binary Dissipative Collisions (BDC)

– BDC opens around the Fermi energy

– σBDC > 95% σREAC

Irrespectively of - event centrality - system size - system mass

asymmetry

V.M

etiv

ier

et a

l . (I

ND

RA

Co l

labo

rat i

o n),

Nuc

l . P

hys.

A67

2 (2

000)

357

.

QP emission in BDCs

J. P

eter

et a

l ., N

u cl .

Ph y

s. A

593

(199

5) 9

5.

Reconstructed primary QP mass approxim. . equal to the projectile mass

Thus obtained primary QP extremely hot

Y. -

G. M

a et

al . ,

Ph y

s. L

ett .

B39

0 (1

997)

41.

Ar (95 MeV/u) Ni

Statistical emission component

Ph .

Eud

es a

nd Z

. Bas

rak,

Eu r

. Phy

s. J

. A 9

(20

00)

207.

Landau-Vlasov model simulationAr ( 65 MeV / u ) Al

The geniune primary QP emission

Ar (65 MeV/u) Al

D. Cussol et al., Nucl. Phys. A561 (1993) 298.

J. Peter et al., Nucl. Phys. A593 (1995) 95.

Heat & compression

– Maximal compression at ~25 fm/c

– In each volume cell a local equilibration at ~35 fm/c

– System scission at ~55 fm/c

Despite of the establishment of a local equi-librium throughout the compact system the (Eth/A)sys and (Ath/A)proj differ substantially:

Global equilibrium is far from being reached

I. N

ovos

el e

t al . ,

Ph y

s. L

ett.

B6 2

5 (2

005)

26.

Head-on collisions

A universal linear proportionality law proves the eminent role of “hard” NN collisions.

A targ

(A targ + A proj ) 2Eavail =

c.m. E proj

A proj

A projDependence on available energy

I. N

ovos

el e

t al . ,

Ph y

s. L

ett.

B62

5 (2

005)

26.

Dependence of relative sub-systems Eth/A on incident energy for head-on collisions

I. N

ovos

el e

t al . ,

Ph y

s. L

ett.

B6 2

5 (2

005)

26.Projectile ratio =

(Eth/A)proj

Target ratio =

(Eth/A)sys

(Eth/A)targ

(Eth/A)sys

Ratio of thermal energy maxima


I. N

ovos

el e

t al . ,

Ph y

s. L

ett.

B6 2

5 (2

005)


(Eth/A)proj

Target ratio =

(Eth/A)sys

(Eth/A)targ

(Eth/A)sys

A symmetric system



I. N

ovos

el e

t al . ,

Ph y

s. L

ett.

B6 2

5 (2

005)


(Eth/A)proj

Target ratio =

(Eth/A)sys

(Eth/A)targ

(Eth/A)sys

An asymmetric system



I. N

ovos

el e

t al . ,

Ph y

s. L

ett.

B6 2

5 (2

005)


(Eth/A)proj

Target ratio =

(Eth/A)sys

(Eth/A)targ

(Eth/A)sys

Increasingly asymmetric systems



I. N

ovos

el e

t al . ,

Ph y

s. L

ett.

B6 2

5 (2

005)


(Eth/A)proj

Target ratio =

(Eth/A)sys

(Eth/A)targ

(Eth/A)sys



I. N

ovos

el e

t al . ,

Ph y

s. L

ett.

B6 2

5 (2

005)

26.

tal change from the fusion-deep inelastic into the BDC – partic.-spect,(fireball)-like behavior.

The reaction geo-metry is important in intermediate E HIC.

The Fermi energy is a transient region where the main reac-tion mechanism un-dergoes a fundamen-


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