decay features of medium mass nuclei at high excitation and...
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Simone ValdreUniversita degli studi di FirenzeandINFN — Sezione di Firenze
for the NUCL-EX collaboration
Decay features of medium mass nucleiat high excitation and spins
Comex5, Krakow
September 16th, 2015
1/13
2/13
Introduction Experimental apparatus Statistical model Results Conclusions
Introduction
The reaction
=⇒
Reaction parameters
Eb [MeV] Ecm [MeV] ε∗ [MeV/u] lgr [~] lBf=0 [~]
300 135 1.4 91 79450 203 2.2 124 79600 271 3.0 149 79
3/13
Introduction Experimental apparatus Statistical model Results Conclusions
Introduction
Why 88Mo?
large fission barrier up to high spins
mass region not well explored in literature
GDR study performed here in Krakow
Michal Ciema la talkM. Ciema la et al., Phys. Rev. C 91,054313 (2015)
This talk will be focused on:
light charged particles emission in fusion-evaporation channelcheck of statistical model parametersfusion-evaporation and fusion-fission cross sectionsS. Valdre et al., submitted to Phys. Rev. C. arXiv:1509.03184
3/13
Introduction Experimental apparatus Statistical model Results Conclusions
Introduction
Why 88Mo?
large fission barrier up to high spins
mass region not well explored in literature
GDR study performed here in Krakow
Michal Ciema la talkM. Ciema la et al., Phys. Rev. C 91,054313 (2015)
This talk will be focused on:
light charged particles emission in fusion-evaporation channelcheck of statistical model parametersfusion-evaporation and fusion-fission cross sectionsS. Valdre et al., submitted to Phys. Rev. C. arXiv:1509.03184
4/13
Introduction Experimental apparatus Statistical model Results Conclusions
Experimental apparatus
Experimental apparatus
The experiment
performed at Laboratori Nazionali di Legnaro (LNL)
beam from ALPI linac
Main detectors: Garfield and Hector
4/13
Introduction Experimental apparatus Statistical model Results Conclusions
Experimental apparatus
Experimental apparatus
Garfield
∆E (gas)-E (CsI(Tl)) telescope array
cylindrical symmetry; divided into 24 azimuthal sectors
detects LCPs and IMFs at 29° < θ < 85°
4/13
Introduction Experimental apparatus Statistical model Results Conclusions
Experimental apparatus
Experimental apparatus
Hector
8 BaF2 scintillators from Hector setup
detect high energy γ-rays (Eγ & 4 MeV)
not considered in the present work
4/13
Introduction Experimental apparatus Statistical model Results Conclusions
Experimental apparatus
Experimental apparatus
Phoswiches
48 scintillator telescopes from Fiasco experiment
identify evaporation residues and fission fragments
at forward angles (5° < θ < 15°)
4/13
Introduction Experimental apparatus Statistical model Results Conclusions
Experimental apparatus
Experimental apparatus
Phoswiches
48 scintillator telescopes from Fiasco experiment
identify evaporation residues and fission fragments
at forward angles (5° < θ < 15°)
5/13
Introduction Experimental apparatus Statistical model Results Conclusions
Evaporation residue selection
ToF [ns]20 40 60 80 100 120
gat
eA [
arb
. un
its]
500
1000
1500
2000
2500
a)
elastic scattering
HHe CN
OF
NeNaMgAlSiP
gateB [arb. units]500 1000 1500 2000
gat
eA [
arb
. un
its]
500
1000
1500
2000
2500
b)
elastic scattering
H
HeCNOFNe
NaMg
AlSi
Ptrigger threshold
Condition for the selection of fusion-evaporation events
1 particle in dotted areal gate in any phoswichno other particles in continuous areal gates
6/13
Introduction Experimental apparatus Statistical model Results Conclusions
Statistical model of Compound Nucleus decay
The Gemini++ statistical model code
is a widely used statistical model code
adopts a default set of parameters obtained by fitting datafrom several previous experiments
parameters are tuned for heavy nuclei (A & 150)there aren’t many experimental data to fix parameters formedium-light nuclei
We compared experimental data with Gemini++ varyingmany parameters:
level densityCoulomb barrier distributionyrast energy parametrizationetc. . .
R. J. Charity, Phys. Rev. C 82, 014610 (2010)
7/13
Introduction Experimental apparatus Statistical model Results Conclusions
From 4π to experimental geometry and vice-versa
Geometry and efficiency filter
directly compare experimental spectra with filtered simulations
correct experimental yields for the apparatus efficiency
]° [(lab)θ0 2 4 6 8 10 12 14
[a.
u.]
θdσd
-310
-210
Evaporation residue angular distribution
4π
Filtered
Gemini++
8/13
Introduction Experimental apparatus Statistical model Results Conclusions
Comparison between experimental data and Gemini++
300 and 600 MeV ER angular distributions
Spectra are scaled to the same integral to compare the shape
Very good agreement
8/13
Introduction Experimental apparatus Statistical model Results Conclusions
Comparison between experimental data and Gemini++
300 MeV energy spectra in coincidence with ER
Spectra are scaled to the same integral to compare the shape
Very good agreement for protons
Simulated α spectra have a correct slope, but lower energy
p α
9/13
Introduction Experimental apparatus Statistical model Results Conclusions
Improvement of the agreement for α-particles
Only adopting RLDM yrast and fission barrier(instead of linearized Sierk) the agreement improves
]hJ [0 10 20 30 40 50 60 70 80
E [
MeV
]
01020304050607080 Lin. Sierk Y.
RLDM Y.fSierk B
fRLDM B
Yrast and fission barriers
10/13
Introduction Experimental apparatus Statistical model Results Conclusions
Comparison between experimental data and Gemini++
proton energy spectra at 300 MeV
[MeV](c.m.)E5 10 15 20
[ar
b. u
nit
s]d
Eσd
-210
-110
(a)
exp
GEMINI++
°300MeV p 60
[MeV](c.m.)E10 20
[ar
b. u
nit
s]d
Eσd
-310
-210
-110
(b)
°300MeV p 47
[MeV](c.m.)E0 10 20
[ar
b. u
nit
s]d
Eσd
-310
-210
-110
(c)
°300MeV p 35
α-particle energy spectra at 300 MeV
[MeV](c.m.)E10 20 30 40
[ar
b. u
nit
s]d
Eσd
-210
-110
(d)
° 60α300MeV
[MeV](c.m.)E10 20 30 40
[ar
b. u
nit
s]d
Eσd -310
-210
-110
(e)
° 47α300MeV
[MeV](c.m.)E10 20 30 40
[ar
b. u
nit
s]d
Eσd -310
-210
-110
(f)
° 35α300MeV
10/13
Introduction Experimental apparatus Statistical model Results Conclusions
Comparison between experimental data and Gemini++
proton energy spectra at 450 MeV
[MeV](c.m.)E10 20
[ar
b. u
nit
s]d
Eσd -210
-110
(a)
exp
GEMINI++
°450MeV p 60
[MeV](c.m.)E10 20 30
[ar
b. u
nit
s]d
Eσd-310
-210
-110
(b)
°450MeV p 47
[MeV](c.m.)E0 10 20
[ar
b. u
nit
s]d
Eσd
-210
-110
(c)
°450MeV p 35
α-particle energy spectra at 450 MeV
[MeV](c.m.)E10 20 30
[ar
b. u
nit
s]d
Eσd
-210
(d)
° 60α450MeV
[MeV](c.m.)E10 20 30 40
[ar
b. u
nit
s]d
Eσd
-210(e)
° 47α450MeV
[MeV](c.m.)E10 20 30
[ar
b. u
nit
s]d
Eσd -210 (f)
° 35α450MeV
10/13
Introduction Experimental apparatus Statistical model Results Conclusions
Comparison between experimental data and Gemini++
proton energy spectra at 600 MeV
[MeV](c.m.)E10 20 30
[ar
b. u
nit
s]d
Eσd
-210
-110
(a)
exp
GEMINI++
°600MeV p 60
[MeV](c.m.)E10 20 30
[ar
b. u
nit
s]d
Eσd
-310
-210
-110
(b)
°600MeV p 47
[MeV](c.m.)E0 10 20 30
[ar
b. u
nit
s]d
Eσd
-210
-110
(c)
°600MeV p 35
α-particle energy spectra at 600 MeV
[MeV](c.m.)E10 20 30 40 50
[ar
b. u
nit
s]d
Eσd
-210 (d)
° 60α600MeV
[MeV](c.m.)E10 20 30 40 50
[ar
b. u
nit
s]d
Eσd
-210(e)
° 47α600MeV
[MeV](c.m.)E10 20 30 40
[ar
b. u
nit
s]d
Eσd
-210(f)
° 35α600MeV
10/13
Introduction Experimental apparatus Statistical model Results Conclusions
Comparison between experimental data and Gemini++
proton angular distributions
[deg](lab)θ20 40 60
[ar
b. u
nit
s]Ωdσd
0
0.5
1 (a)
exp
GEMINI++
p 300MeV
[deg](lab)θ20 40 60
[ar
b. u
nit
s]Ωdσd
0
0.5
1 (b)
p 450MeV
[deg](lab)θ20 40 60
[ar
b. u
nit
s]Ωdσd
0
0.5
1 (c)
p 600MeV
α-particle angular distributions
[deg](lab)θ20 40 60
[ar
b. u
nit
s]Ωdσd
0
0.5
1
1.5(d)
300MeVα
[deg](lab)θ20 40 60
[ar
b. u
nit
s]Ωdσd
0
0.5
1
1.5(e)
450MeVα
[deg](lab)θ20 40 60
[ar
b. u
nit
s]Ωdσd
0
0.5
1
1.5(f)
600MeVα
10/13
Introduction Experimental apparatus Statistical model Results Conclusions
Comparison between experimental data and Gemini++
Ebeam [MeV]200 300 400 500 600 700 800
mu
ltip
licit
y
1
2
3
4
5
6p totald total
totalαp from GARFIELDd from GARFIELD
from GARFIELDα
11/13
Introduction Experimental apparatus Statistical model Results Conclusions
Cross section estimations
Rutherford cross-section normalization
It’s possible to measure cross sections via a normalization obtainedfrom a plastic scintillator at 2° that measures elastic scattering
σFE(300 MeV) = 0.89(11) b
σFE(450 MeV) = 0.55(5) b
σFE(600 MeV) = 0.46(12) b
P. Eudes et al., Europhys. Lett. 104, 22001 (2013)
σFEσR
11/13
Introduction Experimental apparatus Statistical model Results Conclusions
Cross section estimations
Rutherford cross-section normalization
It’s possible to measure cross sections via a normalization obtainedfrom a plastic scintillator at 2° that measures elastic scattering
σF(300 MeV) = 1.01(11) b
σF(450 MeV) = 0.81(6) b
σF(600 MeV) = 0.88(16) b
σFσR
12/13
Introduction Experimental apparatus Statistical model Results Conclusions
Conclusions
We measured the reaction 48Ti+40Ca at 300, 450 and 600 MeVto study the decay of nuclei of masses in the region A ∼ 90
Gemini++ statistical model code well describes the decay inthe evaporative channel at least in Garfield (θ > 30°)
We found an α-particle yield excess, in particular at forwardangles and increasing with energy.
It’s difficult to improve the agreement by tuning the modelparameters; indication of the onset of minor pre-equilibriumemission or contamination from other processes.
We gave an estimation of fusion-evaporation and total fusioncross section. Expecially at higher energies, there is room forDIC and quasi-fission decays.
12/13
Introduction Experimental apparatus Statistical model Results Conclusions
Conclusions
We measured the reaction 48Ti+40Ca at 300, 450 and 600 MeVto study the decay of nuclei of masses in the region A ∼ 90
Gemini++ statistical model code well describes the decay inthe evaporative channel at least in Garfield (θ > 30°)
We found an α-particle yield excess, in particular at forwardangles and increasing with energy.
It’s difficult to improve the agreement by tuning the modelparameters; indication of the onset of minor pre-equilibriumemission or contamination from other processes.
We gave an estimation of fusion-evaporation and total fusioncross section. Expecially at higher energies, there is room forDIC and quasi-fission decays.
12/13
Introduction Experimental apparatus Statistical model Results Conclusions
Conclusions
We measured the reaction 48Ti+40Ca at 300, 450 and 600 MeVto study the decay of nuclei of masses in the region A ∼ 90
Gemini++ statistical model code well describes the decay inthe evaporative channel at least in Garfield (θ > 30°)
We found an α-particle yield excess, in particular at forwardangles and increasing with energy.
It’s difficult to improve the agreement by tuning the modelparameters; indication of the onset of minor pre-equilibriumemission or contamination from other processes.
We gave an estimation of fusion-evaporation and total fusioncross section. Expecially at higher energies, there is room forDIC and quasi-fission decays.
12/13
Introduction Experimental apparatus Statistical model Results Conclusions
Conclusions
We measured the reaction 48Ti+40Ca at 300, 450 and 600 MeVto study the decay of nuclei of masses in the region A ∼ 90
Gemini++ statistical model code well describes the decay inthe evaporative channel at least in Garfield (θ > 30°)
We found an α-particle yield excess, in particular at forwardangles and increasing with energy.
It’s difficult to improve the agreement by tuning the modelparameters; indication of the onset of minor pre-equilibriumemission or contamination from other processes.
We gave an estimation of fusion-evaporation and total fusioncross section. Expecially at higher energies, there is room forDIC and quasi-fission decays.
12/13
Introduction Experimental apparatus Statistical model Results Conclusions
Conclusions
We measured the reaction 48Ti+40Ca at 300, 450 and 600 MeVto study the decay of nuclei of masses in the region A ∼ 90
Gemini++ statistical model code well describes the decay inthe evaporative channel at least in Garfield (θ > 30°)
We found an α-particle yield excess, in particular at forwardangles and increasing with energy.
It’s difficult to improve the agreement by tuning the modelparameters; indication of the onset of minor pre-equilibriumemission or contamination from other processes.
We gave an estimation of fusion-evaporation and total fusioncross section. Expecially at higher energies, there is room forDIC and quasi-fission decays.
Thanks for your attention!13/13
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