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Spectroscopic insight into the shape coexistence in 76,78 Sr, (78),80 Zr 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 Letter of Intent for

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

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Shape coexistence along Z=38 and Z=40 Beyond Mean Field calculations show shape coexistence and evolution in p-rich Strontium isotopes:

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Shape coexistence along Z=38 and Z=40 Beyond Mean Field calculations show shape coexistence and evolution in p-rich Strontium isotopes:

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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:

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Scientific Motivation Beyond Mean Field calculations predict shape coexistence in 78 Sr and strong triaxial effects One observes shape-coexistence in 78 Sr 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.

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Scientific Motivation Beyond Mean Field calculations predict shape coexistence in 78 Sr and strong triaxial effects (*) L.Gaudefroy et al. Phys. Rev. C 80, 2009 (*)

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Shape coexistence along Z=40 A=78 N=38 A=80 N=40

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Shape coexistence along Z=40 A=80 N=40 One observes shape-coexistence in 80 Zr, 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 78 Sr!) 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!

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Shape coexistence along Z=40 A=78 N=38 A=80 N=40

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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(E2;J J-2)/B(E2;2 0) X(5) 152 Sm Iachello,Phys.Rev.Lett. 85 (2000), 87 (2001)

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Scientific Motivation Search for the possible empirical realization of X(5) Critical Point Symmetry in 78 Sr X(5) 78 Sr X(5) U(5) SU(3) 78 Sr 10 + Lister et al., Phys. Rev. Lett. 49 (1982) Rudolph et al. Phys. Rev. C, 1997 Gross et al. Phys. Rev. C, 1994

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Spectroscopic insight into the shape coexistence in 78 Sr What can we measure?

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Measurables lifetime values of yrast levels up to 10 + with high accuracy (5%/20%) = 155(19) ps = 5.1(5) ps = ? 78 Sr 80 Zr = ? 76 Sr = ? yrast band livetime measurements at LNL via fusion evaporation yrare band (2+,4+) measurements at GSI via n-knockout/Coulex

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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

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

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Experiment Livetime measurements via line-shape analysis (?) SIS-18 Primary beam: 1 GeV/u 107 Ag 4x10 9 pps 79 Sr AGATA S2 9Be-Target R =0.43 E 79 Sr 78 Sr + n FRS Sec. beams: 100 MeV/u 81 Zr 81 Sr, 79 Sr (to LYCCA) Sec. (pps) 81Zr for (80Zr+n)450 77Sr for (76Sr+n)1.5E3 79Sr for (78Sr+n)1.4E5

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Comparison vs. Pieters MC of 36 K d = 23.5 cm cut [15,25] deg Be (1g/cm2) MeV/u 36 K+n 2+ (3+) 810 keV GS = 0 ps = 15 ps d = cm Be (1g/cm2) MeV/u AGATA RISING

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Summary & Outlook We plan to study deformation, shape coexistence and evolution effects in the 78,80 Zr and 76,78 Sr isotopes. Both and 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 concentrates on the high-spin yrast states of the 76,78 Sr 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 will concentrate on the measurment of the 0 +,2 + (4 + ) yrare states in the 78,80 Zr and 76,78 Sr isotopes.

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END

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Experiment (a) AGATA S2 = 155 ps d = 23.5 cm Be (1g/cm2) x 0.5 ) = 5.1 ps x keV = 1 ps> = 0.12 ps> = 0.1 ps> 78 Sr

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Experiment (a) AGATA S2 = 155 ps d = 23.5 cm Be (1g/cm2) x 0.5 ) = 5.1 ps x keV 2+ = 1 ps> = 0.12 ps> = 0.1 ps> = 155 ps

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Experiment (a) AGATA S2 = 155 ps d = 23.5 cm Be (1g/cm2) x 0.5 ) = 5.1 ps x keV 4+ = 1 ps> = 0.12 ps> = 0.1 ps> = 5.1 ps

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Experiment (a) AGATA S2 = 155 ps d = 23.5 cm Be (1g/cm2) x 0.5 ) = 5.1 ps x keV 6+ = 1 ps = 0.12 ps> = 0.1 ps> = 1 ps

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Comparison vs. Pieters MC of 36 K d = 23.5 cm Be (1g/cm2) MeV/u 36 K+n 2+ (3+) 810 keV GS d = cm Be (1g/cm2) MeV/u = 0 ps = 15 ps

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Comparison vs. Pieters MC of 36 K d = 23.5 cm Be (1g/cm2) MeV/u 36 K+n 2+ (3+) 810 keV GS d = cm Be (1g/cm2) MeV/u = 0 ps = 15 ps

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Comparison vs. Pieters MC of 36 K d = 73.5 cm Be (1g/cm2) MeV/u 36 K+n 2+ (3+) 810 keV GS d = cm Be (1g/cm2) MeV/u = 0 ps = 15 ps

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Comparison vs. Pieters MC of 36 K d = 73.5 cm Be (1g/cm2) MeV/u 36 K+n 2+ (3+) 810 keV GS d = cm Be (1g/cm2) MeV/u = 0 ps = 15 ps

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Comparison vs. Pieters MC of 36 K d = 73.5 cm Be (1g/cm2) MeV/u 36 K+n 2+ (3+) 810 keV GS Recoil at de-excitation time: = 15 ps = 0 ps = 15 ps

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Comparison vs. Pieters MC of 36 K d = 73.5 cm Be (1g/cm2) MeV/u 36 K+n 2+ (3+) 810 keV GS Recoil at de-excitation time: = 15 ps = 0 ps = 15 ps

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Comparison vs. Pieters MC of 36 K d = 73.5 cm Be (1g/cm2) MeV/u 36 K+n 2+ (3+) 810 keV GS = 0 ps = 15 ps d = cm Be (1g/cm2) MeV/u

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Comparison vs. Pieters MC of 36 K d = 73.5 cm Be (1g/cm2) MeV/u 36 K+n 2+ (3+) 810 keV GS = 0 ps = 15 ps d = 23.5 cm Be (1g/cm2) MeV/u 36 K+n 2+ (3+) 810 keV GS = 0 ps = 15 ps

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Summary of 36 K lifetime studies with AGATA S2 (no angular cut!) d = 73.5 cm Be (1g/cm2) MeV/u = 0 ps = 15 ps d = 23.5 cm Be (1g/cm2) MeV/u = 0 ps = 15 ps d = 73.5 cm Be (1g/cm2) MeV/u d = 23.5 cm Be (1g/cm2) MeV/u = 0 ps = 15 ps = 0 ps = 15 ps

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AGATA S2:Efficiency vs. Theta for several distances

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AGATA S2: lineshape effect with and w/o angular cut 36 K+n d = 23.5 cm Be (1g/cm2) MeV/u = 0 ps = 15 ps = 0 ps = 15 ps in [15,25] deg 2+ (3+) 810 keV GS All s

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AGATA S2: angular differential lineshape effect study

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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)

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Level Scheme of 78 Sr D.Rudolph et al. Phys. Rev. C, 1997

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Previous Experimental Work on 78 Sr YearAuthorLaboratoryDetectorReactionResults on 78 Sr 1982 Lister et al. Brookhaven N.L.Ge, Ge(Li) n-detector 58 Ni( 24 Mg,2p2n) 100 MeV yrast J=0 to 10 2+, Gross et al. SERC Daresbury(BGO)Ge n-detector 58 Ni( 24 Mg,2p2n) 110 MeV yrast J=0 to Gross et al. Daresbury Nuc.Str. Facility EUROGAM 40 Ca( 40 Ca,2p) 128 MeV yrast J=0 to Rudolph et al. L.Berkeley N.L.Gammasphere (57CS Ge + Microball) 58 Ni( 28 Si,2p2n) 130 MeV yrast J=0 to 26 negative parity side bands 2007 Davies et al. Argonne N.L.Gammasphere (101 CS Ge + Microball) 40 Ca( 40 Ca,2p2n) 165 MeV 76Sr

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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 (19) (exp. value) (0.5) (exp. value) Expected lifetimes (ps): 78 Sr

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Spectroscopic insight into the shape coexistence in 78 Sr 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 (LNL Proposal 10.25)

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Spectroscopic insight into the shape coexistence in 78 Sr Scientific Motivation

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Search for the possible empirical realization of X(5) Critical Point Symmetry in 78 Sr McCutchan et al. Phys.Rev.C 71 (2005) Casten et al.,Phys.Rev.Lett. 85 (2000) B(E2;J J-2)/B(E2;2 0) X(5) 152 Sm Iachello,Phys.Rev.Lett. 85 (2000), 87 (2001)

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

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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 78 Sr 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

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Spectroscopic insight into the shape coexistence in 78 Sr What can we measure?

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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 (19) (exp. value) (0.5) (exp. value) Expected lifetimes (ps): 78 Sr

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

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Experiment AGATA Demonstrator (5 triple cluster) + Köln Plunger XTU-TANDEM 120 MeV 40 Ca-Beam 1 pnA 40 Ca 40 Ca( 40 Ca, 2p) 78 Sr Ca-target 400 g/cm 2 Au-Degrader 10.5 mg/cm 2 AGATA Demonstrator Köln Plunger Ca-TargetAu-Degrader 40 Ca R =0.04 E E 78 Sr Recoil Distance Doppler Shift Method (RDDS)

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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

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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

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Experiment (a) AGATA Demonstrator (5 triple cluster) + Köln Plunger d = mm 0.01 mm 0.02 mm + Information from thick-target measurement ~ 1 ps x 0.8 ) ~ 1 ps x 0.8 ) 712 keV

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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. gated peak intensity (a.u.)

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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

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Spectroscopic insight into the shape coexistence in 78 Sr How much beam-time is needed?

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Beam-Time estimate J E (keV) (ps) d (mm) -Counts time (h) Total Beam-Time Request = 5 days PLUNGER Thick Target

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Outlook The proposed lifetime measurements may provide the first strong evidence of X(5) quantum phase transition in 78 Sr. These results will be complemented with further yrare band measurements on 78 Sr with AGATA at GSI in 2011/2012. Measured lifetimes or B(E2) values will allow us to study shape coexistence in 78 Sr 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.

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Backup Slides

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Level Scheme of 78 Sr D.Rudolph et al. Phys. Rev. C, 1997 yrast band

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Previous Experimental Work on 78 Sr YearAuthorLaboratoryDetectorReactionResults on 78 Sr 1982 Lister et al. Brookhaven N.L.Ge, Ge(Li) n-detector 58 Ni( 24 Mg,2p2n) 100 MeV yrast J=0 to 10 2+, Gross et al. SERC Daresbury(BGO)Ge n-detector 58 Ni( 24 Mg,2p2n) 110 MeV yrast J=0 to Gross et al. Daresbury Nuc.Str. Facility EUROGAM 40 Ca( 40 Ca,2p) 128 MeV yrast J=0 to Rudolph et al. L.Berkeley N.L.Gammasphere (57CS Ge + Microball) 58 Ni( 28 Si,2p2n) 130 MeV yrast J=0 to 26 negative parity side bands 2007 Davies et al. Argonne N.L.Gammasphere (101 CS Ge + Microball) 40 Ca( 40 Ca,2p2n) 165 MeV 76Sr

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Shape coexistence along Z=38 Beyond Mean Field calculations do predict shape coexistence in 78 Sr and strong triaxial effects

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Beam-Time estimate J E (keV) (ps) d (mm)Countstime (h) Total Beam-Time = 5.6 days PLUNGER Thick Target

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Theoretical Framework BMF (from T.R. Rodriguez)

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Theoretical Framework BMF (from T.R. Rodriguez)

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Theoretical Framework BMF (from T.R. Rodriguez)

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Theoretical Framework BMF (from T.R. Rodriguez)

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