M

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Decay studies of high-energy isoscalar giant
resonances

• Mátyás Hunyadi

ATOMKI Institute of Nuclear Research Debrecen, Hungary
KVI Kerfysisch Versneller Instituut Groningen, The Netherlands
NDU University of Notre Dame Notre Dame, USA
RCNP Research Center for Nuclear Physics Osaka, Japan
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Decay studies of high-energy isoscalar giant
resonances
3h?
2h?
4h?
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Microscopic picture transition operator
Transition operator of a ?-pole isoscalar GR
?0
?1
?2
?3
-
-
2h? ISGQR
3h? ISGOR (HEOR)
1st order
4h? ISGQR2
3h? ISGDR
2h? ISGMR
2nd order
4h? ISGMR2
3rd order
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Isoscalar GR modes historical overview
2h? ISGMR (1977) (a,a) breathing mode (volume density oscillation) compression modulus KA ? K8
3h? ISGDR (1997) (a,a) squeezing mode complementary determination of KA
2h? ISGMR (1989) (a,an) attempts to study neutron-decay channels, but direct-decay, which populates single-hole states, was not purely disentangled from statistical components no decay data for the ISGDR
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Macroscopic picture transition densities
main tone
Hydrodynamic model
EOS
n1
hydrodynamic wave equation
overtone
? density fields ? transition density
compression character
n2
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Surface and volume modes
ISGMR
ISGQR
ISGDR
ISGQR2
n2
n2
n1
n2
M.L. Gorelik et al., PRC69 (2004) 054322
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Isoscalar GR modes experimental difficulties
Analysis singles experiments using (a,a) scattering applied multipole decomposition analysis general problems of background treatment Technical limitations momentum acceptance of spectrometers, instrumental background (QF-scattering at forward angles) Broad, weakly excited (second order) resonance structures
Singles measurements accurate gross
resonance parameters Decay mesurements
suppression of background and continuum
direct information on microstructures
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Evolution and decay of the p-h structure
1p-1h ? CN
statistical G?
direct G?
nh?
A-1
A
total width
CRPA
branching ratio
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Decay of isoscalar modes experimental
limitations
with increasing mass
Ex (MeV)
decreasing width (better peak to background ratio favors the discovery of new, high energy overtone modes) decreasing resonance energy (resonances below the particle thresholds are exluded) less fragmented p-h structure (higher collectivity, more precise systematics on the nuclear incompressibily
A (amu)
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Decay of isoscalar modes experimental
limitations
with decreasing mass
Ex (MeV)
increasing resonance energy (low-energy resonances can also be studied in particle-decay exp.) stronger fragmentation of p-h structures (partial strength distributions are more informative on microstructures
A (amu)
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Experimental setup for proton-decay measurements
at KVI
BBS
Si-ball
beam
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Experimental setup for proton-decay measurements
at RCNP
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Proton-decay spectra 57Co, 89Y, 207Tl
208Pb(a,ap)207Tl
M. Hunyadi et al., Phys. Lett. B 576 (2003) 253
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Neutron-decay spectra 89Zr, 115Sn, 207Pb
decay from the continuum region ( 4h?)
decay from the ISGDR region ( 3h?)
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Angular distributions of direct neuton-decay
gated spectra simplified MDA
decay from the ISGDR region
fit with DWBA calculated angular distributions of
100 EWSR in terms of differential cross-section
L3
L1
branching ratios
singles differential cross-sections
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Singles spectra difference-of-spectra analysis
(DOS)
?
exhaustion of the EWSR
92 21
91 19
122 22
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Branching ratios for the direct neutron-decay
channel
Br (exp)
Br (CRPA)
10.5 5.6
11.46
from the simplified MDA of angular distributions
5.1 0.7
10.85
4.8 0.9
16.8
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Angular distributions of direct neuton-decay
gated spectra
decay from the ISGDR region continuum
region
best fit L2
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Analysis of direct proton-decay branches from
208Pb
L1
L2
L3
best fit L2 (ISGQR2?)
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ISGDR (CRPA)
208Pb
4h? ISGQR2 (CRPA)
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Direct-decay branching ratios for 90Zr
preliminary results!
CRPA predictions M.L. Gorelik et al., PRC69
(2004) 054322
15-19 MeV ISGMR region L0
20-27 MeV ISGDR region L1
21-35 MeV ISGDR region continuum region L2
Ex DOS
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Direct proton-decay gated strength distribution
for the ISGDR in 58Ni
preliminary results!
HEB
LEB
Centroid energies
high-energy bump (HEB)
31.11.5 MeV
for 20ltExlt40 MeV
29.70.8 MeV
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Direct population of hole-states in 57Co from the
ISGDR strength
preliminary results!
test of p-h state distribution calculated by CRPA
LEB
HEB
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Summary outlook
Systematics of KA in closed shell nuclei
? increased precision of K8
(N-Z)/A-dependence of KA in long isotopic chains
? K8 at ?0 neutron matter EOS
Particle decay measurements direct feeding of
single-hole states especially for more fragmented
resonances in low-A nuclei
direct decay branching ratios partial strength
distributions (p-h states, collectivity)
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Summary outlook
confirmation of L2 strength in the 4h? region in
208Pb indication of ISGQR2 supported by CRPA
predictions a new compression mode! partial
proton-decay branching ratios and total
direct neutron-decay branching ratios test
CRPA-model assumptions in medium-heavy and heavy
nuclei p-h structure may be revealed in
moderately fragmented ISGDR strength in 58Ni
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Thank you!

• Participants

ATOMKI M. Csatlós, L. Csige, J. Gulyás, M. Hunyadi, A. Krasznahorkay, D. Sohler, A. Vitéz
KVI A.M. van den Berg, M.N. Harakeh, M.A. de Huu, A. Matic, H.J. Wörtche
NDU U. Garg, T. Li, B.K. Nayak, J. Hoffman
RCNP H. Akimune, H. Fujimura, M. Fujiwara, K. Hara, M. Itoh, K. Nakanishi, H. Sakaguchi, H. Takeda, M. Uchida, Y. Yasuda, M. Yosoi