isotopic effects on the level density and symmetry energy ...lea-colliga/public-docs/2008... · mc...
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Isotopic effects on the level density and symmetry Isotopic effects on the level density and symmetry energy: an experimental perspectiveenergy: an experimental perspective
Measurements at Ebeam 10-20 AMeV allow to measure the symmetry energy at finite temperature near the
saturation density
LoI presented to the Legnaro PAC for a campaign of measurements starting in 2009
Isotopic effects on the level density and symmetry Isotopic effects on the level density and symmetry energy: an experimental perspectiveenergy: an experimental perspective
Bao-An Li PRC74(2006)034610Skyrme Hartree-Fock
Y.Alhassid et al. PRL 79(1997)2939MC Shell Model
Isotopic effects on the level density and symmetry Isotopic effects on the level density and symmetry energy: an experimental perspectiveenergy: an experimental perspective
Bao-An Li PRC74(2006)034610Skyrme Hartree-Fock
Y.Alhassid et al. PRL 79(1997)2939MC Shell Model
Ebeam ≈102 AGeVEbeam ≈50 AMeV
Isotopic effects on the level density and symmetry Isotopic effects on the level density and symmetry energy: an experimental perspectiveenergy: an experimental perspective
Measurements at ρ ≈ ρ0 and moderate ε*,T are
missing
Bao-An Li PRC74(2006)034610Skyrme Hartree-Fock
Y.Alhassid et al. PRL 79(1997)2939MC Shell Model
Ebeam ≈102 AGeVEbeam ≈50 AMeV
Isotopic effects on the level density and symmetry Isotopic effects on the level density and symmetry energy: an experimental perspectiveenergy: an experimental perspective
Experiments@ALPI-LNL (Ebeam≈ 15 AMeV) can build the a bridge between reaction mechanisms and structure:
evaporation chains are expected to be short => IMF yields can be corrected to access the finite temperature physics
Bao-An Li PRC74(2006)034610Skyrme Hartree-Fock
Y.Alhassid et al. PRL 79(1997)2939MC Shell Model
Experiments@ALPIExperiments@ALPI-- Central collisionsCentral collisions
J. Pochodzalla et al., P.R.L. 75 (1995)1040;
C. Sfienti et al., Nucl.Phys. A734(2004) 528
In this energy range in central
collisions one can observe :
• evaporation events (ρ≈ρ0)
• multifragmentation events (ρ<ρ0).
Due to “more expensive”
Q-values associated to many
fragment partitions, the excitation
energy of primary fragments is
expected to be low.
ReactionElab
(A.MeV)θ θ θ θ grazing
σσσσ fus.
(mb)A Z N/Z c.n.
E*
(A.MeV)
(14,28)Si + (28,58)Ni 19 6 425 80 39 1.05 3.8
(16,32)S + (28,58)Ni 17 7 470 84 41 1.05 3.6
(20,40)Ca + (28,58)Ni 16 7 480 91 45 1.02 3.7
(20,48)Ca + (28,64)Ni 16 6 570 103 44 1.34 3.8
(28,58)Ni + (28,58)Ni 13 9 565 109 53 1.06 3.2
(29,63)Cu + (28,58)Ni 12 9 630 116 54 1.15 3.0
Ring
counter
GARFIELD deviceGARFIELD device-- new setupnew setup
•High granularity (~400 ∆E-E telescopes ϑ ≈4o-150o)
•Low energy thresholds (ionization chambers as ∆E)
•Z identification: ϑ ≈ 4o-150o
•A and Z identification:
(1<=Z<=12) ϑ ≈ 4o - 20o (Si-CsI digital pulse shape)
(Z=1-3) ϑ ≈ 30o - 150o (CsI digital pulse-shape)
•Digital electronics also for gas detectors
Garfield@ALPI: Garfield@ALPI: 3232S+S+58,6458,64Ni at 14.5 AMeV Ni at 14.5 AMeV Data (~complete events,central collisions)Data (~complete events,central collisions)
largest fragment
2nd largest
3rd largest
Garfield@ALPI: Garfield@ALPI: 3232S+S+58,6458,64Ni at 14.5 AMeV Ni at 14.5 AMeV Data (~complete events,central collisions) & model comparisonData (~complete events,central collisions) & model comparison
MODEL:breakup
Microcanonical Multifragmentation Model (Ad.Raduta):
source=90% of (Ap+At), ε*=3 A MeV
only normalization to the number of events
Garfield@ALPI: Garfield@ALPI: 3232S+S+58,6458,64Ni at 14.5 AMeV Ni at 14.5 AMeV Data (~complete events,central collisions) & model comparisonData (~complete events,central collisions) & model comparison
MODEL:finalMODEL:breakup
Microcanonical Multifragmentation Model (Ad.Raduta):
source=90% of (Ap+At), ε*=3 A MeV
only normalization to the number of events
Garfield@ALPI: Garfield@ALPI: 3232S+S+58,6458,64Ni at 14.5 AMeV Ni at 14.5 AMeV Data (~complete events,central collisions) & model comparisonData (~complete events,central collisions) & model comparison
MODEL:finalMODEL:breakup
Measured final products are produced by short de-excitation chains
Microcanonical Multifragmentation Model (Ad.Raduta):
source=90% of (Ap+At), ε*=3 A MeV
Questions:Questions:
Questions:Questions:
At ε*≈1 AMeV, do structure effects appear in evaporation/fragmentation?
Questions:Questions:
At ε*≈1 AMeV, do structure effects appear in evaporation/fragmentation?
If yes:�Which is their intensity?
Questions:Questions:
At ε*≈1 AMeV, do structure effects appear in evaporation/fragmentation?
If yes:�Which is their intensity?�Up to which E* are they apparent?
Questions:Questions:
At ε*≈1 AMeV, do structure effects appear in evaporation/fragmentation?
If yes:�Which is their intensity?�Up to which E* are they apparent?�Are they present in other reactions?
Questions:Questions:
At ε*≈1 AMeV, do structure effects appear in evaporation/fragmentation?
If yes:�Which is their intensity?�Up to which E* are they apparent?�Are they present in other reactions?
Answers provide information for higher energy experiments and fragmentation models!!!!!!!!!!
Garfield@ALPI: Garfield@ALPI: 3232S+S+58,6458,64Ni 14.5 AMeVNi 14.5 AMeVRaw calculation of the symmetry energy Raw calculation of the symmetry energy
σσ22ZZ (A) (A) ≈≈ A T /[2 Csym(T,A)]A T /[2 Csym(T,A)]
M.Colonna, B.Tsang; Eur. Phys. J. A 30 (2006) 165
Ad.Raduta,F.Gulminelli; PRC75 (2007) 044605
A word of caution:A word of caution:Csym refers to the hot fragments
σ, T experimentally come from cold IMFs.
Garfield@ALPIGarfield@ALPI: : 3232S+S+58,6458,64Ni 14.5 AMeVNi 14.5 AMeVRaw calculation of the symmetry energy Raw calculation of the symmetry energy
σσ22ZZ (A) (A) ≈≈ A T /[2 Csym(T,A)]A T /[2 Csym(T,A)]
Odd-even effects in Csym
(in the isotope widths)?
M.Colonna, B.Tsang; Eur. Phys. J. A 30 (2006) 165
Ad.Raduta,F.Gulminelli; PRC75 (2007) 044605
Garfield@ALPIGarfield@ALPI: : 3232S+S+58,6458,64Ni 14.5 AMeVNi 14.5 AMeVRaw calculation of the symmetry energy Raw calculation of the symmetry energy
σσ22ZZ (A) (A) ≈≈ A T /[2 Csym(T,A)]A T /[2 Csym(T,A)]
Odd-even effects in Csym
(in the isotope widths)?
M.Colonna, B.Tsang; Eur. Phys. J. A 30 (2006) 165
Ad.Raduta,F.Gulminelli; PRC75 (2007) 044605
E.Geraci et al.,NPA732 (2004) 173
and paper in preparation
Ni58 +Sn112 35 AMeV (open points)
Ni64 +Sn124 35 AMeV (full points)
Garfield@ALPIGarfield@ALPI: : 3232S+S+58,6458,64Ni 14.5 AMeVNi 14.5 AMeVRaw calculation of the symmetry energy Raw calculation of the symmetry energy
σσ22ZZ (A) (A) ≈≈ A T /[2 Csym(T,A)]A T /[2 Csym(T,A)]
Odd-even effects in Csym
(in the isotope widths)?
M.Colonna, B.Tsang; Eur. Phys. J. A 30 (2006) 165
Ad.Raduta,F.Gulminelli; PRC75 (2007) 044605
E.Geraci et al.,NPA732 (2004) 173
and paper in preparation
Ni58 +Sn112 35 AMeV (open points)
Ni64 +Sn124 35 AMeV (full points)
The Z-odd-even effect has been observed also in other observables
Z oddZ odd--even anomaly @GSI and ALPIeven anomaly @GSI and ALPI
238U
56Fe
124Sn
107Sn
GSI FRS inclusive data
W.Trautmann-NN2006, V.Ricciardi-NPDC18 2004,
C.Sfienti-NUFRA2007
Garfield@ALPI 32S+58Ni 14.6 AMeV
An enhancement for even-Z fragments observed from spontaneous fission to the breakup of AGeV heavy projectiles.
Pairing effects acting in the last steps of the evaporation chain only partially explained this anomaly.
Z oddZ odd--even anomaly @GSI and ALPIeven anomaly @GSI and ALPI
238U
56Fe
124Sn
107Sn
GSI FRS inclusive data
W.Trautmann-NN2006, V.Ricciardi-NPDC18 2004,
C.Sfienti-NUFRA2007
Garfield@ALPI 32S+58Ni 14.6 AMeV
The anomaly seems to be:
• independent of the beam energy and of the centrality of the events,
Z oddZ odd--even anomaly @GSI and ALPIeven anomaly @GSI and ALPI
238U
56Fe
124Sn
107Sn
GSI FRS inclusive data
W.Trautmann-NN2006, V.Ricciardi-NPDC18 2004,
C.Sfienti-NUFRA2007
Garfield@ALPI 32S+58Ni 14.6 AMeV
The anomaly seems to be:
• independent of the beam energy and of the centrality of the events,
• slightly depending on the number of neutrons,
Z oddZ odd--even anomaly @GSI and ALPIeven anomaly @GSI and ALPI
238U
56Fe
124Sn
107Sn
GSI FRS inclusive data
W.Trautmann-NN2006, V.Ricciardi-NPDC18 2004,
C.Sfienti-NUFRA2007
Garfield@ALPI 32S+58Ni 14.6 AMeV
The anomaly seems to be:
• independent of the beam energy and of the centrality of the events,
• slightly depending on the number of neutrons,
• more pronounced in Ni reactions,
Z oddZ odd--even anomaly @GSI and ALPIeven anomaly @GSI and ALPI
238U
56Fe
124Sn
107Sn
GSI FRS inclusive data
W.Trautmann-NN2006, V.Ricciardi-NPDC18 2004,
C.Sfienti-NUFRA2007
Garfield@ALPI 32S+58Ni 14.6 AMeV
The anomaly seems to be:• independent of the beam energy and of the centrality of the events,• slightly depending on the number of neutrons,• more pronounced in Ni reactions,• absent in reactions involving stable Ca,Kr,Xe projectile and targets.
Ca projectile and/or target:Ca projectile and/or target:
G.Cardella (private communication)
Limiting experimentLimiting experiment--LNS Cyclotron LNS Cyclotron -- Inclusive dataInclusive data
Ca projectile and/or target:Ca projectile and/or target:
G.Cardella (private communication)
Limiting experimentLimiting experiment--LNS Cyclotron LNS Cyclotron -- Inclusive dataInclusive data
Cross fertilization between data and evaporation modelsCross fertilization between data and evaporation models
Cross fertilization between data and evaporation modelsCross fertilization between data and evaporation models
� Staggering comes from pairing effects in the binding energies & level density in the last evaporation steps(model):sucheffect must be controlled to access Csym at finite T
A=87 Z=40 e*=3 A.MeV
Microcanonical Multifragmentation Model:
source=90% of (Ap+At), ε*=3 A MeV
A=87 Z=40 e*=3 A.MeVA=87 Z=40 e*=3 A.MeV
Break-up
Asymptotic
Cross fertilization between data and evaporation modelsCross fertilization between data and evaporation models
� Staggering comes from pairing effects in the binding energies & level density in the last evaporation steps(model):sucheffect must be controlled to access Csym at finite T
� The staggering amplitude depends on the relative excited state population in neighbor nuclei at low ε* (data)
A=87 Z=40 e*=3 A.MeV
Microcanonical Multifragmentation Model:
source=90% of (Ap+At), ε*=3 A MeV
Break-up
Asymptotic
Cross fertilization between data and evaporation modelsCross fertilization between data and evaporation models
� Staggering comes from pairing effects in the binding energies & level density in the last evaporation steps(model):sucheffect must be controlled to access Csym at finite T
� The staggering amplitude depends on the relative excited state population in neighbor nuclei at low ε* (data)
� The contribution from discrete particle-unstable levels is dominant for even-even nuclei, and can be traced back from correlations (data)
A=87 Z=40 e*=3 A.MeV
Microcanonical Multifragmentation Model:
source=90% of (Ap+At), ε*=3 A MeV
Break-up
Asymptotic
Cross fertilization between data and evaporation modelsCross fertilization between data and evaporation models
� Staggering comes from pairing effects in the binding energies & level density in the last evaporation steps(model):sucheffect must be controlled to access Csym at finite T
� The staggering amplitude depends on the relative excited state population in neighbor nuclei at low ε* (data)
� The contribution from discrete particle-unstable levels is dominant for even-even nuclei, and can be traced back from correlations (data)
� Back-tracing the decay through evaporation models: the tuning between data and model will be done by comparing measured and calculated resonance probabilities. (data+model)
A=87 Z=40 e*=3 A.MeV
Microcanonical Multifragmentation Model:
source=90% of (Ap+At), ε*=3 A MeV
Break-up
Asymptotic
Last stage of the decay revealed by correlation functions of Last stage of the decay revealed by correlation functions of the relative momentumthe relative momentum
Observed 23 resonances from Li* to O*, ε* up to 1.5 AMeV +4He* at ε* =24 MeV
Last stage of the decay revealed by correlation functions of Last stage of the decay revealed by correlation functions of the relative momentumthe relative momentum
Observed 23 resonances from Li* to O*, ε* up to 1.5 AMeV +4He* at ε* =24 MeV
To properly backtrace primary fragments,
we have to extract the probability for a pair
to come from a resonance-decay.
A problem is to separate resonant and
uncorrelated yields
(F.Grenier,A.Chbihi et al. NPA(2008) in press)
Last stage of the decay revealed by correlation functions of Last stage of the decay revealed by correlation functions of the relative momentumthe relative momentum
Observed 23 resonances from Li* to O*, ε* up to 1.5 AMeV +4He* at ε* =24 MeV
for each resonance, by gaussian fits,
we extracted the probability for a pair
to come from a resonance-decay
(e.g. 23% for α-d)
THeLi thermometer corrections!!!
BacktraceBacktrace of the last step of the decayof the last step of the decay
From the probability for a pair to be
generated by a resonance-decay, we
calculated for each mother nucleus the
average decay probability and excitation
energy
odd-Z nuclei mainly decay by emitting p,d
even-Z mainly by emitting α
BacktraceBacktrace of the last step of the decayof the last step of the decay
from the probability for a pair to be
generated by a resonance-decay, we
calculated for each mother nucleus the
average decay probability and excitation
energy
The decay probability results higher
and E* lower for odd than for even Z
Summary, perspectivesSummary, perspectives
� Odd-even effects in the level densities result in staggering in different isotopic observables
� Correlations: an experimental constraint of excited levels population should help disentangling the influence of the binding energy and the level density in the observed staggering.
� Back-tracing the decay through evaporation models: the tuning between data and model will be done by comparing measured and calculated resonance probabilities.
� This study can be performed for different classes of event (evaporation-fragmentation) for reactions involving projectile and targets from Ca to Ni
Summary, perspectivesSummary, perspectives
� Odd-even effects in the level densities result in staggering in different isotopic observables
� Correlations: an experimental constraint of excited levels population should help disentangling the influence of the binding energy and the level density in the observed staggering.
� Back-tracing the decay through evaporation models: the tuning between data and model will be done by comparing measured and calculated resonance probabilities.
� This study can be performed for different classes of event (evaporation-fragmentation) for reactions involving projectile and targets from Ca to Ni
Break-up
Asymptotic
A=87 Z=40 ε*=3 A.MeV
Summary, perspectivesSummary, perspectives
� Odd-even effects in the level densities result in staggering in different isotopic observables
� Correlations: an experimental constraint of excited levels population should help disentangling the influence of the binding energy and the level density in the observed staggering.
� Back-tracing the decay through evaporation models: the tuning between data and model will be done by comparing measured and calculated resonance probabilities.
� This study can be performed for different classes of event (evaporation-fragmentation) for reactions involving projectile and targets from Ca to Ni
Break-up
Asymptotic
A=87 Z=40 ε*=3 A.MeV
At this stage At this stage Csym(TCsym(T) )
could be accessiblecould be accessible
Isotopic effects on the level density and symmetry Isotopic effects on the level density and symmetry energy: an experimental perspectiveenergy: an experimental perspective
LoI presented to the Legnaro PAC for a campaign starting in 2009
“The committee felt that this is an important line of research for the Laboratory to
pursue both for the understanding of existing data on multi-fragmentation and also
for future work, which will be carried out in this field, using radioactive beam
facilities such as EURISOL.”
In view of next proposals comments, suggestions from your side are
warmly acknowledged!
M.D’Agostino (Bologna Univ. and INFN)
thanks to: Nuclex collaboration, F.Gulminelli (Caen Univ. and LPC),
Ad.Raduta (NIPNE-Bucharest), E.Geraci(Catania Univ. and INFN)
Garfield@ALPIGarfield@ALPI: : 3232S+S+58,6458,64Ni 14.5 AMeV Ni 14.5 AMeV -- Event selectionEvent selection
),(i,j wppTk
M
k
k
j
k
iij31
)(
1
)()(=∑=
=
J.Cugnon,NPA(1985)
PCA analysis;For events where Ztot >70% ZP+T
and θflow >60 o (central collisions)
1. Comparison with models, source characterization (Z,A,ε*,T, ρ)
2. Isotope analysis for different classes of events
Garfield@ALPIGarfield@ALPI: : 3232S+S+58,6458,64Ni 14.5 AMeV Ni 14.5 AMeV -- Event selectionEvent selection
),(i,j wppTk
M
k
k
j
k
iij31
)(
1
)()(=∑=
=
J.Cugnon,NPA(1985)
PCA analysis;For events where Ztot >70% ZP+T
and θflow >60 o (central collisions)
1. Comparison with models, source characterization (Z,A,ε*,T, ρ)
2. Isotope analysis for different classes of events
Garfield@ALPIGarfield@ALPI: : 3232S+S+58,6458,64Ni 14.5 AMeV Ni 14.5 AMeV -- Event selectionEvent selection
),(i,j wppTk
M
k
k
j
k
iij31
)(
1
)()(=∑=
=
J.Cugnon,NPA(1985)
PCA analysis;For events where Ztot >70% ZP+T
and θflow >60 o (central collisions)
1. Comparison with models, source characterization (Z,A,ε*,T, ρ)
2. Isotope analysis for different classes of events
He4 24.2 d + d
Li6 2.186 d + α
Be8 g.s. α + α
Be8 17.64 p + Li7
Be9 2.43 α + α + n
Be9 16.97, 17.3, 17.5 p + Li8
B10 5.166 α + Li6
B11 11.35,11.44,11.59,11.89 p + Be10
C11 8.70,9.8 α + Be7
C12 27.9 p + n + B10
C12 16.5,17.3 p + B11
C14 12.96 α + Be10
N12 1.19 p + C11
N13 2.36 p + C12
N14 8.01,9.17 p + C13
N14 11.21 d + C12
N14 13.3 α + B10
N15 11.62 α + B11
O15 10.3 α + C11
O16 8.87 α + C12
O17 7.17,7.76 α + C13
O18 7.12 α + C14
F19 4.65 α + N15
23 resonances
ε* from 0.1 to 1.5 AMeV
odd-Z nuclei mainly decay through p,d emission
even-Z mainly through α
ZZ--oddodd--even anomalyeven anomaly
Garfield@ALPIGarfield@ALPI 3232S+S+58,6458,64Ni 15 AMeVNi 15 AMeV
G.Cardella (private communication)
Limiting experimentLimiting experiment--LNS CyclotronLNS Cyclotron
Inclusive dataInclusive data
How to backtrace the decay?