Spectroscopic insight into the shape coexistence in 76,78Sr, (78),80Zr

1
Spectroscopic insight into the shape coexistence
in 76,78Sr, (78),80Zr
Letter of Intent for AGATA_at_GSI
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-Dobon INFN, 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. Rother Institut fuer Kernphysik der
Universitaet zu Köln, Köln, Germany A. Algora,
A. Gadea, B. Rubio, J.L. Tain IFIC Instituto de
Fisica Corpuscular, Valencia, Spain
2
Spectroscopic insight into the shape coexistence
in 76,78Sr, (78),80Zr
Scientific Motivation
3
Shape coexistence along Z38 and Z40

• Beyond Mean Field calculations show shape
  coexistence and evolution in p-rich Strontium
  isotopes

4
Shape coexistence along Z38 and Z40

• Beyond Mean Field calculations show shape
  coexistence and evolution in p-rich Strontium
  isotopes

5
Shape coexistence along Z38 and Z40

• Beyond Mean Field calculations show shape
  coexistence and evolution in p-rich Strontium
  isotopes

and Zirconium isotopes
A80 N40
6
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 (K0) yield a rather
  rotational spectrum compared to the experiment.
  Including triaxial effects in the BMF calculation
  should bring the energy of Jgt0 states lower, thus
  giving a better agreement with the experiment.

7
Scientific Motivation

• Beyond Mean Field calculations predict shape
  coexistence in 78Sr and strong triaxial effects

()
() L.Gaudefroy et al. Phys. Rev. C 80, 2009
8
Shape coexistence along Z40
A80 N40
9
Shape coexistence along Z40
A80 N40

• 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!

10
Shape coexistence along Z40
A80 N40
11
Scientific Motivation

• Study the possible X(5) character of these
  NZ38,40 Sr and Zr isotopes

X(5) 152Sm
Casten et al.,Phys.Rev.Lett. 85 (2000)
E.A. McCutchan et al. Phys.Rev.C 71 (2005)
Iachello,Phys.Rev.Lett. 85 (2000), 87 (2001)
12
Scientific Motivation

• Search for the possible empirical realization of
  X(5) Critical Point Symmetry in 78Sr

10
Rudolph et al. Phys. Rev. C, 1997
Gross et al. Phys. Rev. C, 1994
U(5)
X(5)
X(5)
SU(3)
78Sr
Lister et al., Phys. Rev. Lett. 49 (1982)
13
Spectroscopic insight into the shape coexistence
in 78Sr
What can we measure?
14
Measurables

• lifetime values of yrast levels up to 10 with
  high accuracy (5/20)

t ?
t ?
t ?
t ?
t ?
t ?
t ?
t ?
t ?
t 5.1(5) ps
t ?
t ?
t ?
t ?
t 155(19) ps
78Sr
80Zr
76Sr

• yrast band livetime measurements at LNL via
  fusion evaporation
• yrare band (2,4) measurements at GSI via
  n-knockout/Coulex

15
Measurables

• lifetime values of yrast levels up to 10 with
  high accuracy (5/20)

LNL
GSI

• 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

16
Spectroscopic insight into the shape coexistence
in 78Sr
How can we measure it?
17
Experiment

• Livetime measurements via line-shape analysis (?)

AGATA S2
FRS Sec. beams 100 MeV/u 81Zr 81Sr, 79Sr
SIS-18 Primary beam 1 GeV/u 107Ag 4x109 pps
79Sr
Sec. Frag. I_at_S4 (pps)
81Zr for (80Zrn) 450
77Sr for (76Srn) 1.5E3
79Sr for (78Srn) 1.4E5
78Sr n
Eg
79Sr
(to LYCCA)
bR0.43
9Be-Target
18
Comparison vs. Pieters MC of 36K
AGATA
RISING
37Ca _at_ 150 MeV/u
37Ca _at_ 150 MeV/u
36Kn
810 keV
(3)
d 23.5 cm cut qg 15,25 deg Be (1g/cm2)
d 70-140 cm Be (1g/cm2)
GS
2
t 0 ps t 15 ps
19
Summary Outlook

• We plan to study deformation, shape coexistence
  and evolution effects in the 78,80Zr and 76,78Sr
  isotopes.
• Both AGATA_at_LNL and AGATA_at_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_at_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_at_GSI will
  concentrate on the measurment of the 0,2(4)
  yrare states in the 78,80Zr and 76,78Sr isotopes.

20
END
21
Experiment (a)
d 23.5 cm Be (1g/cm2)

• AGATA S2

ltt 0.1 psgt
t x 0.5
2
4
ltt 0.12 psgt
6
8
10
ltt 1 psgt
t 5.1 ps
t 155 ps
278 keV
78Sr
(t x 0.5)
22
Experiment (a)
d 23.5 cm Be (1g/cm2)

• AGATA S2

ltt 0.1 psgt
2
t 155 ps
t x 0.5
ltt 0.12 psgt
ltt 1 psgt
t 5.1 ps
t 155 ps
278 keV
(t x 0.5)
23
Experiment (a)
d 23.5 cm Be (1g/cm2)

• AGATA S2

ltt 0.1 psgt
4
t 5.1 ps
t x 0.5
ltt 0.12 psgt
ltt 1 psgt
t 5.1 ps
t 155 ps
278 keV
(t x 0.5)
24
Experiment (a)
d 23.5 cm Be (1g/cm2)

• AGATA S2

ltt 0.1 psgt
6
t 1 ps
t x 0.5
ltt 0.12 psgt
ltt 1 psgt
t 5.1 ps
t 155 ps
278 keV
(t x 0.5)
25
Comparison vs. Pieters MC of 36K
37Ca _at_ 150 MeV/u
37Ca _at_ 150 MeV/u
36Kn
810 keV
(3)
d 23.5 cm Be (1g/cm2)
d 70-140 cm Be (1g/cm2)
GS
2
t 0 ps t 15 ps
26
Comparison vs. Pieters MC of 36K
37Ca _at_ 150 MeV/u
37Ca _at_ 150 MeV/u
36Kn
810 keV
(3)
d 23.5 cm Be (1g/cm2)
d 70-140 cm Be (1g/cm2)
GS
2
t 0 ps t 15 ps
27
Comparison vs. Pieters MC of 36K
37Ca _at_ 150 MeV/u
37Ca _at_ 150 MeV/u
36Kn
810 keV
(3)
d 73.5 cm Be (1g/cm2)
d 70-140 cm Be (1g/cm2)
GS
2
t 0 ps t 15 ps
28
Comparison vs. Pieters MC of 36K
37Ca _at_ 150 MeV/u
37Ca _at_ 150 MeV/u
36Kn
810 keV
(3)
d 73.5 cm Be (1g/cm2)
d 70-140 cm Be (1g/cm2)
GS
2
t 0 ps t 15 ps
29
Comparison vs. Pieters MC of 36K
37Ca _at_ 150 MeV/u
bRecoil at de-excitation time
36Kn
810 keV
(3)
d 73.5 cm Be (1g/cm2)
t 15 ps
GS
2
t 0 ps t 15 ps
t 0 ps
30
Comparison vs. Pieters MC of 36K
37Ca _at_ 200 MeV/u
bRecoil at de-excitation time
36Kn
810 keV
t 15 ps
(3)
d 73.5 cm Be (1g/cm2)
GS
2
t 0 ps t 15 ps
t 0 ps
31
Comparison vs. Pieters MC of 36K
37Ca _at_ 200 MeV/u
37Ca _at_ 150 MeV/u
36Kn
810 keV
(3)
d 73.5 cm Be (1g/cm2)
d 70-140 cm Be (1g/cm2)
GS
2
t 0 ps t 15 ps
32
Comparison vs. Pieters MC of 36K
37Ca _at_ 200 MeV/u
37Ca _at_ 200 MeV/u
36Kn
36Kn
810 keV
(3)
d 73.5 cm Be (1g/cm2)
d 23.5 cm Be (1g/cm2)
GS
2
t 0 ps t 15 ps
t 0 ps t 15 ps
33
Summary of 36K lifetime studies with AGATA S2
(no angular cut!)
37Ca _at_ 150 MeV/u
37Ca _at_ 150 MeV/u
t 0 ps t 15 ps
t 0 ps t 15 ps
d 73.5 cm Be (1g/cm2)
d 23.5 cm Be (1g/cm2)
t 0 ps t 15 ps
34
AGATA S2Efficiency vs. Theta for several
distances
35
AGATA S2Efficiency vs. Theta for several
distances
36
AGATA S2 lineshape effect with and w/o angular
cut
36Kn
d 23.5 cm Be (1g/cm2)
37Ca _at_ 200 MeV/u
q in 15,25 deg
37Ca _at_ 200 MeV/u
All qs
t 0 ps t 15 ps
t 0 ps t 15 ps
37
AGATA S2 angular differential lineshape effect
study
38
AGATA S2 angular differential lineshape effect
study
d 23.5 cm Be (1g/cm2)
q in 15,25 deg
t 0 ps t 15 ps
q in 35,45 deg
q in 45,55 deg
39
Level Scheme of 78Sr
D.Rudolph et al. Phys. Rev. C, 1997
40
Previous Experimental Work on 78Sr
Year 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 J0 to 10 t2, t4
1989 Gross et al. SERC Daresbury (BGO)Ge n-detector 58Ni(24Mg,2p2n) 110 MeV yrast J0 to 18
1994 Gross et al. Daresbury Nuc.Str. Facility EUROGAM 40Ca(40Ca,2p) 128 MeV yrast J0 to 22
1997 Rudolph et al. L.Berkeley N.L. Gammasphere (57CS Ge Microball) 58Ni(28Si,2p2n) 130 MeV yrast J0 to 26 negative parity side bands
2007 Davies et al. Argonne N.L. Gammasphere (101 CS Ge Microball) 40Ca(40Ca,2p2n) 165 MeV 76Sr
41
Measurables

• lifetime values of yrast levels up to 10 with
  high accuracy (5/20)

t ?
t ?
t ?
Expected lifetimes (ps)
SU(3) X(5) U(5) BMF
2 155 (19) (exp. value) 155 (19) (exp. value) 155 (19) (exp. value) 155 (19) (exp. value)
4 5.1(0.5) (exp. value) 5.1(0.5) (exp. value) 5.1(0.5) (exp. value) 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
t 5.1(5) ps
t 155(19) ps
78Sr
42
Spectroscopic insight into the shape coexistence
in 78Sr
(LNL Proposal 10.25)
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. Sahin INFN, 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. Rother Institut für Kernphysik der
Universität zu Köln, Köln, Germany A.Gadea, A.
Algora, B. Rubio, J.L. Tain IFIC Instituto de
Fisica Corpuscular, Valencia, Spain
43
Spectroscopic insight into the shape coexistence
in 78Sr
Scientific Motivation
44
Scientific Motivation

• Search for the possible empirical realization of
  X(5) Critical Point Symmetry in 78Sr

X(5) 152Sm
Casten et al.,Phys.Rev.Lett. 85 (2000)
McCutchan et al. Phys.Rev.C 71 (2005)
2 4 6 8 10
Iachello,Phys.Rev.Lett. 85 (2000), 87 (2001)
45
Scientific Motivation

• Search for the possible empirical realization of
  X(5) Critical Point Symmetry in 78Sr

10
Rudolph et al. Phys. Rev. C, 1997
Gross et al. Phys. Rev. C, 1994
U(5)
X(5)
X(5)
SU(3)
Lister et al., Phys. Rev. Lett. 49 (1982)
46
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
47
Spectroscopic insight into the shape coexistence
in 78Sr
What can we measure?
48
Measurables

• lifetime values of yrast levels up to 10 with
  high accuracy (5/20)

t ?
t ?
Expected lifetimes (ps)
t ?
SU(3) X(5) U(5) BMF
2 155 (19) (exp. value) 155 (19) (exp. value) 155 (19) (exp. value) 155 (19) (exp. value)
4 5.1(0.5) (exp. value) 5.1(0.5) (exp. value) 5.1(0.5) (exp. value) 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
t 5.1(5) ps
t 155(19) ps
78Sr
49
Spectroscopic insight into the shape coexistence
in 78Sr
How can we measure it?
50
Experiment

• AGATA Demonstrator (5 triple cluster) Köln
  Plunger

AGATA Demonstrator
40Ca
XTU-TANDEM 120 MeV 40Ca-Beam 1 pnA
Recoil Distance Doppler Shift Method (RDDS)
Köln Plunger
40Ca(40Ca, 2p)78Sr
78Sr
Ca-target 400 mg/cm2 Au-Degrader 10.5 mg/cm2
51
Experiment (a)

• AGATA Demonstrator (5 triple cluster) Köln
  Plunger

d 0.2 mm 2 mm 4 mm
t 155(19) ps
t x 0.95
t 155(19) ps
278 keV
(t x 0.95)
MC Code by E. Farnea and C. Michelagnoli
52
Experiment (a)

• AGATA Demonstrator (5 triple cluster) Köln
  Plunger

d 0.03 mm 0.06 mm 0.10 mm
t 5.1(5) ps
(t x 0.95)
t 5.1(5) ps
(t x 0.95)
503 keV
MC Code by E. Farnea and C. Michelagnoli
53
Experiment (a)

• AGATA Demonstrator (5 triple cluster) Köln
  Plunger

d 0.008 mm 0.01 mm 0.02 mm
t 1 ps
(t x 0.8)
t 1 ps
(t x 0.8)
712 keV
Information from thick-target measurement
54
Experiment (a)

• AGATA Demonstrator (5 triple cluster) Köln
  Plunger

Differential Decay Curve (DDC) Analysis Method
rel. gated peak intensity (a.u.)
712 keV
503 keV
278 keV
distance target-degrader (mm)
55
Experiment (b)

• AGATA Demonstrator (5 triple cluster) Thick
  Target

t 0.12 ps
t 0.1 ps
(t x 0.8)
t 0.1 ps
(t x0.8)
(t x0.8)
1058 keV
t 0.12 ps
(t x 0.8)
895 keV
MC Code by E. Farnea and C. Michelagnoli
56
Spectroscopic insight into the shape coexistence
in 78Sr
How much beam-time is needed?
57
Beam-Time estimate
Jp Eg (keV) t (ps) d (mm) gg-Counts time (h)
2 277.6 155 0.2 1432 5.3
2 277.6 155 2 1452 5.4
2 277.6 155 4 1509 5.6
4 503.2 5.1 0.03 1178 8.7
4 503.2 5.1 0.06 1214 9.0
4 503.2 5.1 0.10 1182 8.7
6 712 1.0 0.008 1037 7.7
6 712 1.0 0.010 1036 7.6
6 712 1.0 0.020 992 7.3
8 895 0.12 0 5449 5353 40
10 1058 0.1 0 5449 5353 40
PLUNGER
Thick Target
Total Beam-Time Request
5 days
58
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.

59
Backup Slides
60
Level Scheme of 78Sr
yrast band
D.Rudolph et al. Phys. Rev. C, 1997
61
Previous Experimental Work on 78Sr
Year 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 J0 to 10 t2, t4
1989 Gross et al. SERC Daresbury (BGO)Ge n-detector 58Ni(24Mg,2p2n) 110 MeV yrast J0 to 18
1994 Gross et al. Daresbury Nuc.Str. Facility EUROGAM 40Ca(40Ca,2p) 128 MeV yrast J0 to 22
1997 Rudolph et al. L.Berkeley N.L. Gammasphere (57CS Ge Microball) 58Ni(28Si,2p2n) 130 MeV yrast J0 to 26 negative parity side bands
2007 Davies et al. Argonne N.L. Gammasphere (101 CS Ge Microball) 40Ca(40Ca,2p2n) 165 MeV 76Sr
62
Shape coexistence along Z38

• Beyond Mean Field calculations do predict shape
  coexistence in 78Sr and strong triaxial effects

63
Beam-Time estimate
Jp Eg (keV) t (ps) d (mm) Counts time (h)
2 277.6 155 0.2 1432 5.3
2 277.6 155 2 1452 5.4
2 277.6 155 4 1509 5.6
4 503.2 5.1 0.03 1178 8.7
4 503.2 5.1 0.06 1214 9.0
4 503.2 5.1 0.10 1182 8.7
6 712 1.0 0.008 1037 7.7
6 712 1.0 0.010 1036 7.6
6 712 1.0 0.020 992 7.3
8 895 0.12 0 9535 9368 70
10 1058 0.1 0 9535 9368 70
PLUNGER
Thick Target
Total Beam-Time
5.6 days
64
Theoretical Framework BMF
(from T.R. Rodriguez)
65
Theoretical Framework BMF
(from T.R. Rodriguez)
66
Theoretical Framework BMF
(from T.R. Rodriguez)
67
Theoretical Framework BMF
(from T.R. Rodriguez)