The XI International Conference NN 2012
INFN –LNS and Sezione di Napoli
Istituto Nazionale
di Fisica Nucleare
Fragment emission in Ca+Ca reactions
at 25 MeV/nucleon
Ivano Lombardo
(EXOCHIM Collaboration)
Dip. di Scienze Fisiche, Università di Napoli “Federico II”
INFN – Sezione di Napoli
E-mail: [email protected]
[email protected]
San Antonio, 29/05/2012
Frontiers of Nuclear Physics
INFN –LNS and Sezione di Napoli
Equation of State (EoS) of asymmetric NM e (r, I)
 topics in nuclear structure and dynamics
 relevant role also in astrophysics
Large densities  structure and stability of Neutron Stars
Low densities 
n-rich cluster formation
in Supernovae explosions
J.M. Lattimer and M.Prakash, Science 304 (2004) 536
K.Sumiyoshi and G.Ropke, Phys. Rev. C 77 (2008) 055804
An interdisciplinary topic
How do we probe the (asy)- EoS?
INFN –LNS and Sezione di Napoli
Competition between
reaction mechanisms
at semi-central <b>
Neutron content of light
isotopes inclusively
emitted
Amplitude of even-odd
staggering on Charge
and N distributions
Evaporat.
Residue
Emission
Fragment
production
Isospin transport
process in peripheral
collisions
P
T
Compare reactions
having various:
• N/Z of projectile
• N/Z of target
• N/Z of total system
Explore the maximum
range available ( RIB)
Pre-equilibrium GDR
emission
Pre-equilibrium n/p ratio
Pigmy Dipole Resonance
(A)Symmetry Term of Nuclear Equation of State
Review: M. Di Toro et al, JoP G 37 (2010)
The experiments Limiting & Isospin-1
To investigate these topics  limiting experiment …
INFN –LNS and Sezione di Napoli
Three reactions @ 25 MeV / nucleon:
40Ca
+ 40Ca, 40Ca + 48Ca, 40Ca + 46Ti
(1°) N/Z effects on evaporation residue emission:
F. Amorini et al, Phys. Rev. Lett. 102 (2009)
I. Lombardo et al, Int. Jour. Mod. Phys. E 19 (2010)
(2°) Influence on thermodynamical parameters:
I. Lombardo et al, Nucl. Phys. A 834 (2010)
(3°) Influence on light cluster emission & isospin transport:
I. Lombardo et al, Phys. Rev. C 82 (2010)
.. and as an extension  Isospin-1 experiment
Two reactions @ 25 MeV / nucleon:
48Ca
+ 48Ca, (48Ca + 40Ca)
(1°) N/Z effects on heavy residue emission an the symmetry potential of EOS:
I. Lombardo et al, Acta Phys. Pol. B 42 (2011)
I. Lombardo et al, submitted to Phys. Rev. C
(2°) Light fragments emitted:
I. Lombardo et al, Int. Jour. Mod. Phys. E 20 (2011)
I. Lombardo et al, Phys. Rev. C 84 (2011)
Large range of N/Z involved
INFN –LNS and Sezione di Napoli
Details on the Chimera array
Exp. technique
We measure:
DE - E
Z (all) e M (up to Z
≈10 or more)
ToF
M (fragments
stopped in Si)
Fast-Slow on CsI(Tl)
Z and M of LCP
Pulse Shape in Si
Z (fragments stopped
in Si)
BEAM
688 TELESCOPES
504
TELESCOPES
40Ca+48Ca
Electronic multiplicity trigger m>3
0.8<Ztot/Zi<1 and ppar_tot>70%
48Ca+48Ca
A. Pagano et al, Nucl. Phys. A 734 (2004) 504
Isotopic effects on inclusive emission of fragments
In the very n-rich 48Ca+48Ca system  n-richForward-angle
fragments largely
emitted
emission:
5.2°<q<15.3°
1.E+07
1.E+07
counts/sr (arb. un.)
counts/sr (arb. un.)
7Li
8Li
1.E+06
1.E+05
1.E+04
1.E+03
10B
48Ca+48Ca
1.E+06
N/Z=1.4
11B
12B
13B
40Ca+48Ca
1.E+05
N/Z=1.2
1.E+04
40Ca+40Ca
1.E+03
N/Z=1.0
1.E+02
0
20
40
q
Lab
60
80
0
0.5
(deg)
0.45
20
q = 9.3°
40
q
Lab
60
80
(deg)
48Ca+48Ca
1.E+07
1.E+07
1.E+05
1.E+04
1.E+03
1.E+02
0
20
40
q
Lab
(deg)
60
80
counts/sr (arb. un.)
7Be
1.E+06
11C
0.4
9Be
relative yields
counts/sr (arb. un.)
INFN –LNS and Sezione di Napoli
6Li
12C
0.351.E+06
13C
14C
0.3
15C
48Ca+40Ca
40Ca+48Ca
40Ca+40Ca
1.E+05
0.25
0.21.E+04
0.15
1.E+03
0.1
0
10
0.05
20
q
Lab
30
40
(deg)
0
11
12
13
A of Carbon
Large isotopic effects
14
15
Inclusive emission: staggering
N/Z increases
Even-odd effects:
B. Gatty et al, Nucl. Phys. A 253 (1975) 511
C. Beck et al, Zeit. Phys. A 343 (1992)
G. Lanzanò et al, Zeit. Phys. A 343 (1992) 429
Sl. Cavallaro et al, Phys. Rev. C 57 (1998) 731
K. X. Jing et al, Nucl. Phys. A 645 (1999) 203
L.B. Yang et al, Phys. Rev. C 60 (1999) 041602
E.M. Winchester et al, Phys. Rev. C 63 (2000)
E. Geraci et al, Nucl. Phys. A 734 (2004) 524
P. Napolitani, from Audi & Wapstra
M.V. Ricciardi et al, Nucl. Phys. A 749 (2005)
Jun Su
al, (2005)
Phys. Rev.
M.V. Ricciardi et al, Nucl. Phys.
Aet
749
122C 83 (2011)
G. Ademard et al, Phys. Rev. C 83 (2011)
S. Pirrone et al, EPJ Web1p
Conf. 1n
17 (2011)
s
R. Ogul et al, Phys. Rev.s C 83 (2011)
M. D’Agostino et al, Nucl. Phys. A 861 (2011) 47
P. Napolitani et al, Jour. Phys. G 38 (2011)
Even isotopes and isotones have large
one particle separation energy
I. Lombardo et al, PRC 84 (2011)
De-excitation of highly excited fragments
N/Z decreases
INFN –LNS and Sezione di Napoli
Inclusive emission of light fragments at forward angles (solid lines qmed=11.5°, dashed
lines qmed=16.5°) identifyed by means of DE-E: even-odd effects on Z and N distributions
min{E ,E }
keV
Central collisions: heavy residue emission
INFN –LNS and Sezione di Napoli
Central events (mcp ≥ 5, 6) with the presence of a fast quasi-projectile (v2 or v3>0.13c)
(massive transfer). Mass – velocity correlations of the largets fragment emitted:
The observed phenomenon can
not be attributed to mass effects 
48Ca and 46Ti have similar masses
N/Z=1.4
N/Z=1.2
The N/Z degree of freedom
strongly influences the
reaction mechanisms:
• Larger N/Z  larger heavy
residue emission in Incomplete
Fusion events
N/Z=1.05
N/Z=1.0
Check system
N/Z effects in reaction mechanisms
• Lower N/Z  binary-like,
fusion-fission and IMF emission
prevail
INFN –LNS and Sezione di Napoli
Central collisions: competitive mechanisms
m1  m2
DM

nor
Percentage
moftotHR events by
integrating DMnor > 0.4
DMlarge
disentangle
nor analysis
N/Z 
enhan.
of HR the
competition of various mechanisms
in central
collisions:
symmetric
system  suppr. HR
Relative yields of HR emission in
central collisions by means of two
gaussian fit of experimental mass
spectra:
• large N excess  HRs increase
• N ≈ Z  BL and IMF prevail
This effect can be attributed to the
interplay between Coulomb and
Symmetry terms  nuclear dynamics
Submitted to PRC
in inset
 CoMD-II model
mlines
fusion-like
large DMnor
1 m
2
calculations
m1
m2
Binary-like
Multi-fragm.
Fusion-fission
low DMnor
Central collisions: CoMD-II calculations
Stiff2  g=1
INFN –LNS and Sezione di Napoli
m2<10
m2<10
limiting experiment:
We compared experimental DMnor
distributions with CoMD-II (+GEMINI)
model calculations  we adopted various
form factors of Usym(r/r0)
48Ca+48Ca
m2<10
DM nor 
m1  m2
mtot
 r 
r
F  

 r 0 Stiff 2 r 0
 r 
F    r r 0
 r 0 Soft
2
 r 
2r r 0 
F  

 r 0 Stiff 1 1  r r 0
Best agreement  Stiff2 option.
The GEMINI stage does not change the
overall shape of spectra  dynamics
F. Amorini et al, PRL 102 (2009)
M. Papa and G. Giuliani, EPJ A39 (2009)
experiment
Apparent temperature in ICF events
INFN –LNS and Sezione di Napoli
Similar results  limiting exp.
Newlim exp  under investigation
Weak effect of N/Z on T
inverse slope parameters obtained
from the fit are in good agreement
with systematics
Fuchs e Mohring, Rep. Prog. Phys. 57 (1994)
ICF
NN (pre-eq.)
QP
ICF source
Apparent T
Pre-equilibrium
Inverse slope
40Ca
+ 40Ca
5.3 ± 0.5 MeV
9.3 ± 0.3 MeV
40Ca
+ 46Ti
5.2 ± 0.3 MeV
9.2 ± 0.3 MeV
40Ca
+ 48Ca
5.4 ± 0.4 MeV
9.3 ± 0.3 MeV
Apparent temperature in ICF events
Double isotopic ratio method for apparent temperature estimates
INFN – Laboratori Nazionali del Sud – Catania
S. Albergo et al, Nuovo Cim. A 89 (1985)
• For each systems, the obtained
apparent temperatures are quite
constant as a function of polar
emission angle  no source
mixing
• Apparent temperatures are
quite similar for the studied
systems
THe Li 
TLi C 
11.5

Y /Y
ln  5.9 6 Li 7 Li
 Y11C / Y12C



Weak effect of N/Z on T
13.3

Y /Y
ln 2.18 6 Li 7 Li
Y3 He / Y4 He

TC C 
13.8
 Y /Y
ln  7.9 12C 13C
 Y11C / Y12C






• Differences of <T> for the three
used thermometers  due
probably to secondary emission +
finite size effects
M. B. Tsang et al, PRL 78 (1997) 3836
A. Kolomiets et al, PRC 54 (1996) 472R
W. Trautmann et al, PRC 76 (2007) 064606
Semi-peripheral collisions: isospin diffusion
N/ZQP
N/ZMV
INFN –LNS and Sezione di Napoli
48Ca
N/ZQT
N/ZQP
40Ca
N/ZMV
N/ZQT
N/ZQP
48Ca
N/ZMV
N/ZQT
N/ZQP
40Ca
N/ZMV
N/ZQT
N/Z of QP and MV source  light isobars
Semi-peripheral collisions: isospin diffusion
INFN –LNS and Sezione di Napoli
N/Z of QP (and MV)  7Li/7Be
Is the N/Z equilibrium complete?
7Li
48Ca+48Ca
7Be
48Ca+48Ca
QP:  isospin diffusion
MV  neutron enrichment (isospin
drift)
<b> ≈ 6-7 fm
7Li
and 7Be emission yields by means of
multi-component moving source fits.
Incomplete N/Z equilibrium
see also I. Lombardo et al, PRC 82 (2010)
Semi-peripheral collisions: isospin diffusion
Following SM, we can assume:
Y7 Li
INFN –LNS and Sezione di Napoli
Y7 Be
 exp
N
Z
source
and we can estimate (roughly)
the degree of N/Z equilibrium
Following Keksis et al PRC 81
(2010), we can define the fraction
of equilibrium as follows:
N
N

Z QP Z P
f eq 
N
N

Z TOT Z P
At complete charge
equilibrium  feq=1
The pure systems  useful to
trace the “equilibrium line”
CoMD-II, Stiff2
<feq> ≈ 0.63
Summary and conclusions
INFN –LNS and Sezione di Napoli
• N/Z effects on nuclear reactions can be explored by colliding nuclei with large
differences in N/Z; in our case 40,48Ca+40,48Ca at 25 MeV/nucleon
• Even-odd effects on Z and N distributions  Evaporation stage of excited
fragments
• Nuclear dynamics seems to strongly depend on N/Z values of entrance channels.
The balance between ER and other mechanisms in semi-central events depends
strongly on the neutron richness of entrance channels.
• Dynamical calculations (CoMD-II model) reproduce the experimental mass
spectra, and indicate a stiff dependence of the symmetry energy in nuclear EoS at low
density
• Weak dependence of thermodynamical parameters on the N/Z of entrance channels
• Isospin diffusion signals were obtained by looking at light isobar yields emitted by
QP source in semi-peripheral collisions  non complete N/Z equilibrium (preliminary
results)  estimate of the fraction of equilibrium reached
Thank you for the attention !
INFN –LNS and Sezione di Napoli
Exochim Collaboration
L. Acostaa, C.Agodia, F.Amorinia,c, A.Anzalonea, L. Auditorel, I.Berceanui,
M.Buscemia,c, G.Cardellab, S.Cavallaroa,c, M.B.Chatterjeed, E.De Filippob, G.Giulianic,
E.Geracib,c, L.Grassib,c, J. Hana, E.La Guidarab,e, G.Lanzalonea,f, I.Lombardom,
D.Lorial, C.Maiolinoa, A.Paganob, M.Papab, S.Pirroneb, G.Politib,c, F.Portoa,c, E. Rosatom,
F.Rizzoa,c, P.Russottoa,c, A.Trifiròl, M.Trimarchil, G.Verdeb, M. Vigilantem
a) INFN Laboratori Nazionali del Sud, Catania, Italy
b) INFN, Sezione di Catania, Catania, Italy
c) Dipartimento di Fisica e Astronomia Università di Catania, Catania, Italy
d) Saha Institute of Nuclear Physics, Kolkata, India
e) Centro Siciliano di Fisica Nucleare e Struttura della Materia, Catania, Italy
f) Dipartimento di Ingegneria ed Architettura,Università Kore di Enna, Enna, Italy
g) Institut de Physique Nucleaire d'Orsay, CNRS-IN2P3, Orsay Cedex, France
h) Institute of Physics, University of Silesia, Katowice, Poland
i) Institute for Physics and Nuclear Engineering, Bucharest, Romania
l) Dipartimento di Fisica, Università di Messina, Messina, Italy
m) Dipartimento di Fisica, Università di Napoli Federico II, Napoli, Italy
and INFN – Sezione di Napoli, Via Cintia, Napoli, Italy
INFN –LNS and Sezione di Napoli
Further Slides
p,d,t emission in coincidence with ER
INFN –LNS and Sezione di Napoli
We selected events with Evaporation Residue emission (mER> 0.55mtot) is seen.
Isotopic composition of
hydrogens at qcm>40°
LCP evaporated by ICF
sources
 d/p, t/p and t/d ratios are
strongly connected with the
N/Z of the entrance channels
 the ICF sources have N/Z
contents that reflect very well
the initial N/Z rank
 pre-equilibrium does not
modify the original N/Z rank
Evaporated LCP  N/Z of the excited source
p,d,t emission in coincidence with ER
INFN –LNS, Catania and Sezione di Napoli
We selected events with Evaporation Residue emission (mER> 0.55mtot) is seen.
Isotopic composition of
hydrogens at qcm>40°
LCP evaporated by ICF
sources
 d/p, t/p and t/d ratios are
strongly connected with the
N/Z of the entrance channels
trends are qualitatively reproduced by
HIPSE+SIMON calculations
Evaporated LCP  N/Z of the excited source
 the ICF sources have N/Z
contents that reflect very well
the initial N/Z rank
 pre-equilibrium does not
modify the original N/Z rank
Impact parameter selection: mcp
INFN – Laboratori Nazionali del Sud – Catania
Velocity correlations of the two largest fragments emitted
vp
40Ca
+ 46Ti
v = vproj
v ≈ vtarg
Gentle collisions
v ≈ vproj
vCN < v < vproj
Damped collisions
v <≈ vproj
v ≈ vCN
Very-damped collisions
mcp is correlated to the <b>
INFN – Laboratori Nazionali del Sud – Catania
Collisioni semi-periferiche: trasporto dell’isospin
QP
N/Z1
N/Z2
MV
QT
Nelle collisioni semi-periferiche della
reazione 40Ca+48Ca  notevole
scambio di neutroni tra P e T
(“isospin diffusion”)
Informazioni sull’N/Z dei sistemi
QP e MV (QT soglie) attraverso lo
studio dei rapporti isotopici 7Li/6Li e
9Be/7Be in funzione della v :
par
0.15< vpar/c < 0.23 emissione QP
vpar/c < 0.15
emissione MV
Selezione in mcp  eventi semiperiferici, trend simile osservato nei
dati inclusivi.
40Ca
+ 48Ca
(N/Z=1.2)
40Ca
+ 46Ti
(N/Z=1.05)
Isospin diffusion
40Ca
+ 40Ca
(N/Z=1)
Il QP acquista neutroni dal QT nella
reazione 40Ca+48Ca, rispetto alle
altre due reazioni
Staggering, reaction mechanisms and dissipation
INFN –LNS and Sezione di Napoli
Does the amplitude of the even-odd effect vary as a
function of average dissipation (mLcp)?
40Ca+40Ca
<dissipation>
qmed=11.5°
Kinetic energy of the biggest fragment emitted
Effect of e* on the staggering amplitude?
Symmetry Energy and Symmetry Potential
(A)Symmetry Energy: various notations…
M.F. Rivet, Proc. of Ecole Joliot-Curie (2010)
Baran et al, Phys. Rep. (2005)
Cs , p
2
F ( r / r0 )
Prakash et al, Phys. Rev. Lett. (1988)
Bao An Li et al, Phys. Rep. (2008)
g, F(r/r0) e L sono quantità collegate tra loro
attraverso semplici relazioni matematiche 
stiffness del potenziale di simmetria
• produzione di cluster (bassa densità)
• stabilità delle stelle di neutroni (altissime densità)
An open question
A. Carbone et al, PRC 81, 041301(R) (2010)
INFN –LNS, Catania and Sezione di Napoli
EoS of Asymmetric nuclear matter:
Central collisions: CoMD-II calculations
INFN –LNS and Sezione di Napoli
48Ca+48Ca
experiment
As before, good agreement with Stiff2
option (linear)
By interpolating the three original options,
we find <g> ≈ 1.1 as minimum deviation
from experimental DMnor distributions
Moderately Stiff form factor
QP isoscaling
INFN –LNS and Sezione di Napoli
Study of the isoscaling for QP emission (v// > 0.15c) in 40Ca+40Ca and 48Ca+48Ca
Further analysis to estimate Csym
INFN – Laboratori Nazionali del Sud – Catania
Central collisions: HR emission
DM nor
m1  m2

mtot
Analisi in DMnor  vari processi che
contribuiscono alle collisioni centrali:
emissione di HR per incompleta fusione e
presenza di BL e IMF
Analisi in DMnor su varie finestre di angolo
polare di emissione del frammento m1
HR  emessi preferenzialmente ad angoli
in avanti
Altri processi  emissione di m1 ad angoli
più grandi
Similar results also for 48Ca+48Ca
Apparent temperature in ICF events
INFN –LNS, Catania and Sezione di Napoli
L’N/Z ha influenza sui parametri termodinamici raggiunti dalle sorgenti eccitate
prodotte per incompleta fusione?  Selezione eventi m1≥46 (prod. residui)
Quasi-proiettile
n
a
a
n
n
Pre-eq.
ICF
a
Spettri di velocità di m1  fissare le velocità
delle sorgenti ICF
Fit degli spettri con Maxwelliane di volume:
Metodo utile per estrarre T apparenti: fit a 3 componenti (QP+NN+ICF)
INFN – Laboratori Nazionali del Sud – Catania
Collisioni centrali: stime di energie di eccitazione
Per eventi centrali, con emissione di ER +
particelle leggere (n,p,d,t,3He,a) possiamo
ricostruire lo spettro di E* per nucleone
usando la calorimetria
Bisogna fare ipotesi sulla energia e sulla
molteplicità dei neutroni (legata all’N/Ztot)
che non riveliamo.
Scarsa dipendenza della e* dall’N/Z.
Studi di frammentazione di
proiettili con differente N/Z
hanno mostrato una scarsa
dipendenza della curva calorica
nucleare dal rapporto N/Z
C. Sfienti et al, PRL 102 (2009)
e* simili per I sistemi studiati
Prospettive: uso di Chimera con fasci radioattivi
INFN –LNS, Catania and Sezione di Napoli
Studio dell’emissione di residui in reazioni nucleari a 25 MeV/nucleone con
proiettili di massa media proton rich.
Dal trend della sistematica ottenuta
finora  ci si può aspettare una
notevole soppressione
dell’emissione di residui
Test di produzione e trasporto a
fine Febbraio 2011 alla facility
FRIBS dei LNS-INFN
CHIMERA ROOM
Fascio di partenza: 36Ar
Target di produzione: 9Be
Production
Target
G. Raciti et al, NIM B (2008)
Fragment
Separator
INFN –LNS, Catania and Sezione di Napoli
Produzione di fasci Ar-like
Test di produzione di p-rich nuclei nella regione dell’ Ar
alla facility In-flight di Catania  36Ar (@ 42 MeV/nucleon) +9Be (1.5mm thick,
production target)  Ar-like nuclei at ≈ 25 MeV/nucleon
Con alcune semplici migliorie
sulla linea (già effettuate) ci si
attende:
• 37K  100 kHz
• 35Ar  70 kHz
• 34Cl  >50 kHz
Fasci interessanti anche per studi di struttura
Effetti dell’N/Z sui parametri termodinamici
INFN – Laboratori Nazionali del Sud – Catania
Approccio termodinamico
•
Influenza dell’N/Z sulla temperatura limite;
Besprosvany & Levit PLB (1990)
•
Influenza dell’N/Z sulla e* critica;
Bohne et al, ZPA 347 (1993)
•
Influenza dell’N/Z sulla curva calorica
nucleare.
Sfienti et al, PRL 102 (2009)
DTlim > 1MeV
Calcoli di liquid drop model
“eccitata”
Tlim  competizione dei
termini coulombiano,
superficie e simmetria
g
neutroni (n,g)
INFN – Laboratori Nazionali del Sud – Catania
Isospin-1: check BaF2
Possibilità di estrarre spettri g e neutroni
Per eventi ben ricostruiti di collisioni 48Ca+48Ca, possiamo selezionare (in ToF-RT) i
raggi g; abbiamo anche una calibrazione in energia dei BaF2 con sorgenti 60Co 
spettri di energia dei g per vari meccanismi di reazione
48Ca+48Ca
counts x 1 detector
INFN – Laboratori Nazionali del Sud – Catania
Spettri gamma di bassa energia
m1>54  E.R.
m1<40  B.L.
m3>12  IMF
Work in progress  molteplicità g
q=74°
Sembra che ci sia un
yrast-bump più
pronunciato nel caso di
emissione dei residui
Le pendenze degli spettri g con
energia 2 < Eg < 6 MeV
cambiano (di poco) al cambiare
del meccanismo selezionato
INFN – Laboratori Nazionali del Sud – Catania
Global behavior of events of reactions
Various classes of events
their nature  v1 , v2 correlations
[v1= v(m1) and v2= v(m2)],
• cut on the mass of the largest fragment emitted
• charged particle multiplicity  <b>
Masses of the two largest fragments
m2
m1
m3
We observe mainly events as:
• ER emissions (1XL,2S)
• Binary-like (2L, 1S)
• Ternary (3M), low statistics
Typical behavior of reactions near 20-30 MeV/n