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Spectroscopic insight into the shape coexistence in
76,78Sr, (78),80Zr
P. Boutachkov, C. Domingo-Pardo, H. Geissel, J. Gerl, M. Gorska, E. Merchan, S. Pietri, T.R. Rodriguez, C. Scheidengerger, H.J. Wollersheim
GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany
G. de Angelis, D.R. Napoli, E. Sahin, J.J. Valiente-DobonINFN, Laboratori Nazionali di Legnaro, Legnaro, Italy
S. Aydin, D. Bazzacco, E. Farnea, S. Lenzi, S. Lunardi, R. Menegazzo, D. Mengoni, F. Recchia, C. Ur
Dipartimento di Fisica and INFN, Sezione di Padova, Padova, Italy
A. Dewald, C. Fransen, M. Hackstein, T. Pisulla, W. RotherInstitut fuer Kernphysik der Universitaet zu Köln, Köln, Germany
A. Algora, A. Gadea, B. Rubio, J.L. TainIFIC Instituto de Fisica Corpuscular, Valencia, Spain
Letter of Intent for AGATA@GSI
Spectroscopic insight into the shape coexistence in
76,78Sr, (78),80Zr
Scientific Motivation
Shape coexistence along Z=38 and Z=40• Beyond Mean Field calculations show shape coexistence and evolution in p-rich Strontium isotopes:
Shape coexistence along Z=38 and Z=40• Beyond Mean Field calculations show shape coexistence and evolution in p-rich Strontium isotopes:
Shape coexistence along Z=38 and Z=40• Beyond Mean Field calculations show shape coexistence and evolution in p-rich Strontium isotopes:
A=78
N=38
A=80
N=40
and Zirconium isotopes:
Scientific Motivation • Beyond Mean Field calculations predict shape coexistence in 78Sr and strong triaxial effects
• One observes shape-coexistence in 78Sr with the appearance of a rotational yrast band (build on top of the prolate minimum) and a vibrational band (build on the spherical minimum). The energy difference between both band heads is of about 0.7 MeV.
• These two bands do not mix, the transition probabilities between states of the two different bands are neglibible, as it is reflected by the collective wave-functions.
• The appearance of the rotational band as the Ground State happens after including the beyond mean field correlations (Projection in good angular momentum), which energetically favors the deformed (prolate) minimum rather than the spherical one.
• Axial calculations (K=0) yield a rather rotational spectrum compared to the experiment. Including triaxial effects in the BMF calculation should bring the energy of J>0 states lower, thus giving a better agreement with the experiment.
Scientific Motivation • Beyond Mean Field calculations predict shape coexistence in 78Sr and strong triaxial effects
(*) L.Gaudefroy et al. Phys. Rev. C 80, 2009
(*)
Shape coexistence along Z=40
A=78
N=38
A=80
N=40
Shape coexistence along Z=40
A=80
N=40• One observes shape-coexistence in 80Zr, with one spherical minimum and one prolate minimum separated by a barrier of more than 5 MeV.
• After doing the projection in good angular momentum J, (at variance with 78Sr!) the deformed minimum drops in energy but not enough to become the absolute minimum.
• The deformed state is practically at the same energy as the spherical one. Theoretically, here one can speak of shape coexistence better than anywhere else!
Shape coexistence along Z=40
A=78
N=38
A=80
N=40
Scientific Motivation • Study the possible X(5) character of these N=Z=38,40 Sr and Zr isotopes
E.A. McCutchan et al. Phys.Rev.C 71 (2005)
Casten et al.,Phys.Rev.Lett. 85 (2000)
B(E
2;J
J-
2)/B
(E2;
2
0)
X(5) 152Sm
Iachello,Phys.Rev.Lett. 85 (2000), 87 (2001)
5
np
np
NN
NNP
Scientific Motivation • Search for the possible empirical realization of X(5) Critical Point Symmetry in 78Sr
X(5)
78Sr X(5)
X(5)
U(5)
SU(3)
78Sr
10+
Lister et al., Phys. Rev. Lett. 49 (1982)
Rudolph et al. Phys. Rev. C, 1997
Gross et al. Phys. Rev. C, 1994
5
np
np
NN
NNP
Spectroscopic insight into the shape coexistence in 78Sr
What can we measure?
Measurables• lifetime values of yrast levels up to 10+ with high accuracy (5%/20%)
= 155(19) ps
= 5.1(5) ps
= ?
= ?
= ?
78Sr 80Zr
= ?
= ?
= ?
= ?
= ?
76Sr
= ?
= ?
= ?
= ?
= ?
• yrast band livetime measurements at LNL via fusion evaporation
•yrare band (2+,4+) measurements at GSI via n-knockout/Coulex
Measurables• lifetime values of yrast levels up to 10+ with high accuracy (5%/20%)
• yrast band livetime measurements at LNL via fusion-evaporation reactions
• low-spin yrast and yrare band (2+,4+) measurements at GSI via n-knockout/Coulex
LNL GSI
Spectroscopic insight into the shape coexistence in 78Sr
How can we measure it?
Experiment• Livetime measurements via line-shape analysis (?)
SIS-18
Primary beam:
1 GeV/u 107Ag
4x109 pps
79Sr
AGATA S2’
9Be-Target
R=0.43
E’79Sr
78Sr + n
FRS
Sec. beams:
100 MeV/u
81Zr 81Sr, 79Sr
(to LYCCA)
Sec. Frag. I@S4 (pps)81Zr for (80Zr+n) 450
77Sr for (76Sr+n) 1.5E3
79Sr for (78Sr+n) 1.4E5
Comparison vs. Pieter’s MC of 36K
d = 23.5 cm
cut [15,25] deg
Be (1g/cm2)
37Ca @ 150 MeV/u
36K+n
2+
(3+)810 keV
GS
= 0 ps
= 15 ps
d = 70-140 cm
Be (1g/cm2)
37Ca @ 150 MeV/uAGATA RISING
Summary & Outlook
• We plan to study deformation, shape coexistence and evolution effects in the 78,80Zr and 76,78Sr isotopes.
• Both AGATA@LNL and AGATA@GSI offer complementary possibilities in order to approach this problem in a concomitant way. This means, high-spin yrast states at LNL via Fusion-Evaporation reactions, and low-spin yrast and yrare states at GSI-FRS.
• The experiment proposal for AGATA@LNL concentrates on the high-spin yrast states of the 76,78Sr isotopes. Here we plan to measure the livetimes of the yrast levels up to 10+ by combining Plunger (RDDS) with Thick target (DSAM) techniques.
• The experiment proposal for AGATA@GSI will concentrate on the measurment of the 0+,2+(4+) yrare states in the 78,80Zr and 76,78Sr isotopes.
END
Experiment (a)• AGATA S2’
= 155 ps
d = 23.5 cm
Be (1g/cm2)
x 0.5)
= 5.1 ps
x 0.5
278 keV
2+
4+
6+8+ 10+
= 1 ps>
= 0.12 ps>
= 0.1 ps>
78Sr
Experiment (a)• AGATA S2’
= 155 ps
d = 23.5 cm
Be (1g/cm2)
x 0.5)
= 5.1 ps
x 0.5
278 keV
2+
= 1 ps>
= 0.12 ps>
= 0.1 ps>
= 155 ps
Experiment (a)• AGATA S2’
= 155 ps
d = 23.5 cm
Be (1g/cm2)
x 0.5)
= 5.1 ps
x 0.5
278 keV
4+
= 1 ps>
= 0.12 ps>
= 0.1 ps>
= 5.1 ps
Experiment (a)• AGATA S2’
= 155 ps
d = 23.5 cm
Be (1g/cm2)
x 0.5)
= 5.1 ps
x 0.5
278 keV
6+
= 1 ps
= 0.12 ps>
= 0.1 ps>
= 1 ps
Comparison vs. Pieter’s MC of 36K
d = 23.5 cm
Be (1g/cm2)
37Ca @ 150 MeV/u
36K+n
2+
(3+)810 keV
GS
d = 70-140 cm
Be (1g/cm2)
37Ca @ 150 MeV/u
= 0 ps
= 15 ps
Comparison vs. Pieter’s MC of 36K
d = 23.5 cm
Be (1g/cm2)
37Ca @ 150 MeV/u
36K+n
2+
(3+)810 keV
GS
d = 70-140 cm
Be (1g/cm2)
37Ca @ 150 MeV/u
= 0 ps
= 15 ps
Comparison vs. Pieter’s MC of 36K
d = 73.5 cm
Be (1g/cm2)
37Ca @ 150 MeV/u
36K+n
2+
(3+)810 keV
GS
d = 70-140 cm
Be (1g/cm2)
37Ca @ 150 MeV/u
= 0 ps
= 15 ps
Comparison vs. Pieter’s MC of 36K
d = 73.5 cm
Be (1g/cm2)
37Ca @ 150 MeV/u
36K+n
2+
(3+)810 keV
GS
d = 70-140 cm
Be (1g/cm2)
37Ca @ 150 MeV/u
= 0 ps
= 15 ps
Comparison vs. Pieter’s MC of 36K
d = 73.5 cm
Be (1g/cm2)
37Ca @ 150 MeV/u
36K+n
2+
(3+)810 keV
GS
Recoil at de-excitation time:
= 15 ps
= 0 ps
= 0 ps
= 15 ps
Comparison vs. Pieter’s MC of 36K
d = 73.5 cm
Be (1g/cm2)
37Ca @ 200 MeV/u
36K+n
2+
(3+)810 keV
GS
Recoil at de-excitation time:
= 15 ps
= 0 ps
= 0 ps
= 15 ps
Comparison vs. Pieter’s MC of 36K
d = 73.5 cm
Be (1g/cm2)
37Ca @ 200 MeV/u
36K+n
2+
(3+)810 keV
GS
= 0 ps
= 15 ps
d = 70-140 cm
Be (1g/cm2)
37Ca @ 150 MeV/u
Comparison vs. Pieter’s MC of 36K
d = 73.5 cm
Be (1g/cm2)
37Ca @ 200 MeV/u
36K+n
2+
(3+)810 keV
GS
= 0 ps
= 15 ps
d = 23.5 cm
Be (1g/cm2)
37Ca @ 200 MeV/u
36K+n
2+
(3+)810 keV
GS
= 0 ps
= 15 ps
Summary of 36K lifetime studies with AGATA S2’ (no angular cut!)
d = 73.5 cm
Be (1g/cm2)
37Ca @ 200 MeV/u
= 0 ps
= 15 ps
d = 23.5 cm
Be (1g/cm2)
37Ca @ 200 MeV/u
= 0 ps
= 15 ps
d = 73.5 cm
Be (1g/cm2)
37Ca @ 150 MeV/u
d = 23.5 cm
Be (1g/cm2)
37Ca @ 150 MeV/u = 0 ps
= 15 ps
= 0 ps
= 15 ps
AGATA S2’:Efficiency vs. Theta for several distances
AGATA S2’:Efficiency vs. Theta for several distances
AGATA S2’: lineshape effect with and w/o angular cut
36K+n
d = 23.5 cm
Be (1g/cm2)
37Ca @ 200 MeV/u37Ca @ 200 MeV/u
= 0 ps
= 15 ps
= 0 ps
= 15 ps
in [15,25] deg
2+
(3+)810 keV
GS
All‘s
AGATA S2’: angular differential lineshape effect study
in [25,35] deg
in [35,45] deg
= 0 ps
= 15 ps
in [15,25] deg
in [45,55] deg
AGATA S2’: angular differential lineshape effect study
d = 23.5 cm
Be (1g/cm2)
Level Scheme of 78Sr
D.Rudolph et al. Phys. Rev. C, 1997
Previous Experimental Work on 78SrYear Author Laboratory Detector Reaction Results on
78Sr
1982 Lister
et al. Brookhaven N.L. Ge, Ge(Li)
n-detector
58Ni(24Mg,2p2n)
100 MeV
yrast J=0 to 10
2+, 4+
1989 Gross
et al.SERC Daresbury (BGO)Ge
n-detector
58Ni(24Mg,2p2n)
110 MeV
yrast J=0 to 18
1994 Gross
et al.Daresbury Nuc.Str. Facility
EUROGAM 40Ca(40Ca,2p)
128 MeV
yrast J=0 to 22
1997 Rudolph et al.
L.Berkeley N.L. Gammasphere (57CS Ge + Microball)
58Ni(28Si,2p2n)
130 MeV
yrast J=0 to 26
negative parity side bands
2007 Davies
et al.Argonne N.L. Gammasphere
(101 CS Ge + Microball)
40Ca(40Ca,2p2n)
165 MeV
76Sr
Measurables• lifetime values of yrast levels up to 10+ with high accuracy (5%/20%)
= 155(19) ps
= 5.1(5) ps
= ?
= ?
= ?
SU(3) X(5) U(5) BMF
2+ 155 (19) (exp. value)
4+ 5.1(0.5) (exp. value)
6+ 1.0 0.76 0.50 1.27
8+ 0.19 0.12 0.07 0.39
10+ 0.20 0.11 0.05 0.16
Expected lifetimes (ps):
78Sr
Spectroscopic insight into the shape coexistence in 78Sr
C. Domingo-Pardo, T.R. Rodriguez, P. Boutachkov, J. Gerl, M. Gorska, E. Merchan, S. Pietri, H.J. Wollersheim
GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany
J.J.Valiente-Dobon, G. de Angelis, D.R. Napoli, E. SahinINFN, Laboratori Nazionali di Legnaro, Legnaro, Italy
S. Aydin, D. Bazzacco, E. Farnea, S. Lenzi, S. Lunardi, R. Menegazzo, D. Mengoni, F. Recchia, C. Ur
Dipartimento di Fisica and INFN, Sezione di Padova, Padova, Italy
T. Pisulla, A. Dewald, C. Fransen, M. Hackstein, W. RotherInstitut für Kernphysik der Universität zu Köln, Köln, Germany
A.Gadea, A. Algora, B. Rubio, J.L. TainIFIC Instituto de Fisica Corpuscular, Valencia, Spain
(LNL Proposal 10.25)
Spectroscopic insight into the shape coexistence in 78Sr
Scientific Motivation
Scientific Motivation • Search for the possible empirical realization of X(5) Critical Point Symmetry in 78Sr
McCutchan et al. Phys.Rev.C 71 (2005)
Casten et al.,Phys.Rev.Lett. 85 (2000)
B(E
2;J
J-
2)/B
(E2;
2
0)
X(5) 152Sm
Iachello,Phys.Rev.Lett. 85 (2000), 87 (2001)
5
np
np
NN
NNP
2 4 6 8 10
Scientific Motivation • Search for the possible empirical realization of X(5) Critical Point Symmetry in 78Sr
X(5)
78Sr X(5)
X(5)
U(5)
SU(3)
10+
Lister et al., Phys. Rev. Lett. 49 (1982)
Rudolph et al. Phys. Rev. C, 1997
Gross et al. Phys. Rev. C, 1994
5
np
np
NN
NNP
Scientific Motivation • Quantum Phase Transitions can be also studied from a microscopic perspective e.g. as shown by T.Niksic et al., Phys. Rev. Lett. 99 (2007)
• Beyond Mean Field calculations predict shape coexistence in 78Sr and strong triaxial effects, and can provide quantitative predictions of E(J) or BE2 values.
(*) L.Gaudefroy et al. Phys. Rev. C 80, 2009
(*)
BMF Calculation by T.R. Rodriguez
Spectroscopic insight into the shape coexistence in 78Sr
What can we measure?
Measurables• lifetime values of yrast levels up to 10+ with high accuracy (5%/20%)
= 155(19) ps
= 5.1(5) ps
= ?
= ?
= ?
SU(3) X(5) U(5) BMF
2+ 155 (19) (exp. value)
4+ 5.1(0.5) (exp. value)
6+ 1.0 0.76 0.50 1.27
8+ 0.19 0.12 0.07 0.39
10+ 0.20 0.11 0.05 0.16
Expected lifetimes (ps):
78Sr
Spectroscopic insight into the shape coexistence in 78Sr
How can we measure it?
Experiment• AGATA Demonstrator (5 triple cluster) + Köln Plunger
XTU-TANDEM
120 MeV 40Ca-Beam 1 pnA
40Ca
40Ca(40Ca, 2p)78Sr
Ca-target 400 g/cm2
Au-Degrader 10.5 mg/cm2
AGATA Demonstrator
Köln Plunger
Ca-Target Au-Degrader
40Ca
R=0.04
E’ E
78Sr
Recoil Distance Doppler Shift Method (RDDS)
Experiment (a)• AGATA Demonstrator (5 triple cluster) + Köln Plunger
= 155(19) ps
d = 0.2 mm 2 mm 4 mm
x 0.95)
= 155(19) ps
x 0.95
MC Code by E. Farnea and C. Michelagnoli
278 keV
Experiment (a)• AGATA Demonstrator (5 triple cluster) + Köln Plunger
= 5.1(5) ps
d = 0.03 mm 0.06 mm 0.10 mm
x 0.95)
= 5.1(5) ps x 0.95)
503 keV
MC Code by E. Farnea and C. Michelagnoli
Experiment (a)• AGATA Demonstrator (5 triple cluster) + Köln Plunger
d = 0.008 mm 0.01 mm 0.02 mm
+ Information from thick-target measurement
~ 1 ps
x 0.8)
~ 1 ps
x 0.8)712 keV
Experiment (a)• AGATA Demonstrator (5 triple cluster) + Köln Plunger
712 keV
503 keV
278 keV
Differential Decay Curve (DDC) Analysis Method
distance target-degrader (m)
rel.
gate
d pe
ak in
tens
ity (
a.u.
)
Experiment (b)• AGATA Demonstrator (5 triple cluster) + Thick Target
~ 0.12 ps x 0.8)
~ 0.12 ps x 0.8)
895 keV
~ 0.1 ps
( x0.8)1058 keV
~ 0.1 ps( x0.8)
MC Code by E. Farnea and C. Michelagnoli
Spectroscopic insight into the shape coexistence in 78Sr
How much beam-time is needed?
Beam-Time estimate
J E (keV) (ps)
d (mm) -Counts
time (h)
2+ 277.6 155 0.2 1432 5.3
2 1452 5.4
4 1509 5.6
4+ 503.2 5.1 0.03 1178 8.7
0.06 1214 9.0
0.10 1182 8.7
6+ 712 1.0 0.008 1037 7.7
0.010 1036 7.6
0.020 992 7.3
8+ 895 0.12 0 5449
5353
40
10+ 1058 0.1
Total Beam-Time Request = 5 days
PL
UN
GE
R
Thick Target
Outlook
• The proposed lifetime measurements may provide the first strong evidence of X(5) quantum phase transition in 78Sr.
• These results will be complemented with further yrare band measurements on 78Sr with AGATA at GSI in 2011/2012.
• Measured lifetimes or B(E2) values will allow us to study shape coexistence in 78Sr from a microscopic point of view and they will provide an stringent test for BMF calculations, the predicted triaxiality effect in this nucleus and how the triaxial degree of freedom is included in the calculation.
Backup Slides
Level Scheme of 78Sr
D.Rudolph et al. Phys. Rev. C, 1997
yrast band
Previous Experimental Work on 78SrYear Author Laboratory Detector Reaction Results on
78Sr
1982 Lister
et al. Brookhaven N.L. Ge, Ge(Li)
n-detector
58Ni(24Mg,2p2n)
100 MeV
yrast J=0 to 10
2+, 4+
1989 Gross
et al.SERC Daresbury (BGO)Ge
n-detector
58Ni(24Mg,2p2n)
110 MeV
yrast J=0 to 18
1994 Gross
et al.Daresbury Nuc.Str. Facility
EUROGAM 40Ca(40Ca,2p)
128 MeV
yrast J=0 to 22
1997 Rudolph et al.
L.Berkeley N.L. Gammasphere (57CS Ge + Microball)
58Ni(28Si,2p2n)
130 MeV
yrast J=0 to 26
negative parity side bands
2007 Davies
et al.Argonne N.L. Gammasphere
(101 CS Ge + Microball)
40Ca(40Ca,2p2n)
165 MeV
76Sr
Shape coexistence along Z=38• Beyond Mean Field calculations do predict shape coexistence in 78Sr and strong triaxial effects
Beam-Time estimate
J E (keV)
(ps) d (mm) Counts time (h)
2+ 277.6 155 0.2 1432 5.3
2 1452 5.4
4 1509 5.6
4+ 503.2 5.1 0.03 1178 8.7
0.06 1214 9.0
0.10 1182 8.7
6+ 712 1.0 0.008 1037 7.7
0.010 1036 7.6
0.020 992 7.3
8+ 895 0.12 0 9535
9368
70
10+ 1058 0.1
Total Beam-Time = 5.6 days
PL
UN
GE
R
Thick Target
Theoretical Framework BMF
(from T.R. Rodriguez)
Theoretical Framework BMF
(from T.R. Rodriguez)
Theoretical Framework BMF
(from T.R. Rodriguez)
Theoretical Framework BMF
(from T.R. Rodriguez)