N = Z N=Z line coincides with doubly-magic core Single-particle states wrt 100 Sn core Neutron-proton correlations in identical orbitals Neutron-proton (isoscalar) pairing Emergence of collectivity... Bo Cederwall AGATA Physics WS, Istanbul May 2010 LOI for the AGATA-PRESPEC campaign, GSI Relativistic Coulomb excitation for probing special effects of neutron-proton correlations around 100 Sn B. Cederwall, R. Wadsworth, G. De France et al.

Main physics aims Verify Isoscalar spin-aligned neutron-proton coupling scheme in 92 Pd ( 96 Cd) Verify Isoscalar spin-aligned neutron-proton coupling scheme in 92 Pd ( 96 Cd) Investigate Collective strength in 106,108 Te, 112 Xe Investigate Collective strength in 106,108 Te, 112 Xe by measuring B(E2; 0 + → 2 + ) Builds on our spectroscopic work at GANIL and JYFL and theoretical calculations by J. Blomqvist, R. Liotta, C. Qi, D. Delion et al. Bo Cederwall AGATA Physics WS, Istanbul May 2010

When approaching N=Z, ”normal” pair correlations may remain or even be extended: T=1I=0nnpp Near N=Z we can have T=1, I=0 (”isovector”) nn, pp Cooper pairs np as well as np Cooper pairs (neutrons and protons occupy identical orbits) T=0, I=1... (”isoscalar”) np pairing and/or: T=0, I=1... (”isoscalar”) np pairing Does T=0 pairing exist and, if so, how should it best be revealed? The nature of nuclear pair correlations and their effect on nuclei near N=Z So far, the search for T=0 np pairing has focused on special features: - g.s. binding energies of odd-odd nuclei - high-spin properties of N=Z nuclei (delayed alignments?) - deuteron transfer reactions Bo Cederwall AGATA Physics WS, Istanbul May 2010

The isoscalar (np) pair gap is predicted to increase sharply as N  Z Calculation by W. Satula, R. Wyss Phys. Rev. Lett. Vol. 86, 4488 (2001) Bo Cederwall AGATA Physics WS, Istanbul May 2010

Shell model calculations by J. Blomqvist et al. predict strong T=0 neutron- proton (np) correlations leading to an isoscalar spin-aligned np coupling scheme for N=Z nuclei close to 100 Sn. An ”unexpected effect” of the NSM appearing in this exotic region of the nuclear chart Evidence for onset of collectivity, possibly induced by np pairing* ) in neutron deficient Te and Xe nuclei The proposed experiments aim to confirm these theoretical predictions by measuring B(E2;0+  2+) values. *) M. Sandzelius, B. Hadinia, B. Cederwall, et al., Phys. Rev. Lett. 99, (2007). QRPA + np pairing calculations by D.S. Delion, R. Liotta et al., PRC in press “New” effects of neutron-proton correlations around 100 Sn Bo Cederwall AGATA Physics WS, Istanbul May 2010

What is the g.s. structure of N=Z nuclei below 100 Sn? The conventional picture : Ψ=({νg 9/2 -2 } 0+ ) n x ({πg 9/2 -2 } 0+ ) n This would lead to a normal seniority type spectrum of low-lying excited states νg 9/2 -1 πg 9/2 -1 νg 9/2 -1 πg 9/ Sn 92 Pd For 92 Pd and 96 Cd neutrons and protons mainly occupy the g 9/2 subshell νg 9/2 -1 πg 9/ Sn 96 Cd Bo Cederwall AGATA Physics WS, Istanbul May 2010

Shell Model calculations predict strong np interactions  Transition to new spin-aligned T=0 np coupling scheme for N=Z nuclei below 100 Sn (J. Blomqvist et al.) Ψ=[({νg 9/2 -1 x πg 9/2 -1 } 9+ ) 2 ] 0+ x [({νg 9/2 -1 x πg 9/2 -1 } 7+ ) 2 ] 0+ x [({νg 9/2 -1 x πg 9/2 -1 } 7+ ) 2 ] Sn πg 9/2 -1 νg 9/2 -1 πg 9/2 -1 νg 9/2 -1 πg 9/2 -1 Model space: g 9/2 (and f 5/2, p 3/2,p ½ ) 92 Pd Aligned np coupling: 100 Sn πg 9/2 -1 νg 9/2 -1 πg 9/ Cd Ψ=[({νg 9/2 -1 x πg 9/2 -1 } 9+ ) 2 ] 0+ Bo Cederwall AGATA Physics WS, Istanbul May 2010

Pd level systematics near N=Z Shell model calculations by J. Blomqvist, R. Liotta, C. Qi 92 Pd, theory 92 Pd, exp 94 Pd, exp 94 Pd, theory 96 Pd, theory 96 Pd, exp Bo Cederwall AGATA Physics WS, Istanbul May 2010

Pd level systematics near N=Z - effects of np interactions Bo Cederwall AGATA Physics WS, Istanbul May 2010 Shell model calculations by J. Blomqvist, R. Liotta, C. Qi

New manifestation of T=0 np ”pairing”? 100 Sn l=6 l=8 92 Pd Special deuteron-hole cluster like ground states imply significant deformation ”Nuclear belly dancers” 100 Sn l=8 96 Cd Bo Cederwall AGATA Physics WS, Istanbul May 2010

B(E2; 0 +  2 + ) – sensitive probe of neutron-proton interactions Bo Cederwall AGATA Physics WS, Istanbul May 2010 Shell model calculations by J. Blomqvist, R. Liotta, C. Qi

Enhanced collective strength at N=Z Bo Cederwall AGATA Physics WS, Istanbul May 2010

Evidence for enhanced collective strength in Te and Xe nuclei approaching N=Z T Z =1 nucleus 106 Te : B. Hadinia, B. Cederwall et al., Phys. Rev. C 72, (2005) Bo Cederwall AGATA Physics WS, Istanbul May 2010 Te experimental E(2 + ) and B(E2; 2 + → 0 + )

T Z =1 nucleus 110 Xe; M. Sandzelius, B. Hadinia,, B. Cederwall et al., Phys. Rev. Lett. 99, (2007) Bo Cederwall AGATA Physics WS, Istanbul May 2010 Xe experimental E(2 + ) and B(E2; 2 + → 0 + )

Taken from R.F. Casten, 2003 These trends can change with np pairing as N→Z ! Enhancement of collectivity due to np (short-range) pairing correlations predicted in new calculations by D.S Delion, R. Liotta et al. Quadrupole collectivity Quadrupole collectivity The traditional view of the mechanism behind deformation and collectivity: long range np QQ interactions Bo Cederwall AGATA Physics WS, Istanbul May 2010

New QRPA + np pairing calculations predict enhanced collectivity near the N=Z=50 double shell closure induced by np pairing correlations (D.S. Delion, R. Liotta et al.) p-h excitations induced by np pairing Strong decrease in E(2+) with increasing Δ pn Much smaller effect from long-range QQ np int. Bo Cederwall AGATA Physics WS, Istanbul May 2010

Shell model calculations for light Te isotopes indicate that configuration mixing due to the monopole tensor force between primarily the proton 0g 7/2 and neutron 1d 5/2 orbitals can induce enhanced collectivity (C. Qi, R. Liotta et al.) Bo Cederwall AGATA Physics WS, Istanbul May 2010

Octupole deformation and correlations near N=Z “Doubly-magic octupole-deformed” nucleus predicted by theory Strong octupole correlations are expected in nuclei where normal-parity single-particle states and intruder states differing by Δl = Δj = 3 are near the Fermi surface. Coherent octupole correlations for neutrons and protons should occur near N=Z. Can we observe additional enhancement due to dynamic np correlations ? Next to 112 Ba (accessible with current technology?) 110 Xe 56 and 109 I 56 might have the largest octupole stability.

Enhanced octupole correlations in light Te-Xe nuclei J.F. Smith et al. Phys. Lett B523, 13 (2001) (Gammasphere) G. de Angelis et al. Phys. Lett B535, 153 (2002) (Euroball) G.F. Lane et al. Phys. Rev. C57, R1022 (1998) (Gammasphere) Bo Cederwall AGATA Physics WS, Istanbul May 2010

Measure B(E2; 0 +  2 + ) for isotopic chain 92,94,96 Pd Measure B(E2; 0 +  2 + ) for isotopic chain 92,94,96 Pd (from N=Z to N=50 closed shell) (from N=Z to N=50 closed shell) Measure E(2 + ) for 96 Cd and B(E2; 0 +  2 + ) for 96,98 Cd Measure E(2 + ) for 96 Cd and B(E2; 0 +  2 + ) for 96,98 Cd (from N=Z to N=50 closed shell) (from N=Z to N=50 closed shell) Search for decay of 16 + spin trap isomer for 96 Cd Search for decay of 16 + spin trap isomer for 96 Cd Confirm spin-aligned neutron-proton coupling scheme and characterize np interactions (T=0/T=1) Measure E(2 + ) for 106 Te and B(E2; 0 +  2 + ) for 106,108 Te, 112 Xe Measure E(2 + ) for 106 Te and B(E2; 0 +  2 + ) for 106,108 Te, 112 Xe Measure and characterize collective strength Proposed Experiments Bo Cederwall AGATA Physics WS, Istanbul May 2010

Experimental details Projectile fragmentation FRS – AGATA – LYCCA Pd: LISE++ calc for primary beam 106 Cd E beam = 650 MeV/u I beam = 1 pnA S4 ion and γγ-ion rates Setting 1: optimizing for 92 Pd Setting 2: optimizing for 94 Pd Assume 15% AGATA pp efficiency, σ(Coulex) from DWEIKO Bo Cederwall AGATA Physics WS, Istanbul May 2010 Setting 92 Pd 94 Pd 96 Pd S4 (s -1 ) γ-ion (per day) S4 (s -1 ) γ-ion (per day) S4 (s -1 ) γ-ion (per day) · ·10 4

Experimental details, ct’d Projectile fragmentation FRS – AGATA – LYCCA Cd: LISE++ calc for primary beam 112 Sn E beam = 650 MeV/u I beam = 1 pnA S4 ion and γγ-ion rates Setting optimized for 96 Cd Assume 15% AGATA pp efficiency, σ(Coulex) from DWEIKO Bo Cederwall AGATA Physics WS, Istanbul May Cd 98 Cd S4 (s -1 ) γ-ion (per day) S4 (s -1 ) γ-ion (per day)

Experimental details, ctd’ Projectile fragmentation FRS – AGATA – LYCCA 106,108 Te, 112,114 Xe : LISE++ calc for primary beam 144 Sm E beam = 950 MeV/u I beam = 1 pnA S4 ion and γγ-ion rates Setting 1: optimizing for 106Te Setting 2: optimizing for 112 Xe Assume 15% AGATA pp efficiency, σ(Coulex) from DWEIKO Bo Cederwall AGATA Physics WS, Istanbul May 2010 Setting 106 Te 108 Te 112 Xe 114 Xe S4 (s -1 ) γ-ion (per day) S4 (s -1 ) γ-ion (per day) S4 (s -1 ) γ-ion (per day) S4 (s -1 ) γ-ion (per day) · · · ·10 5

Backup slides Bo Cederwall AGATA Physics WS, Istanbul May 2010

92 Pd analysis (prel) γγ2n Three γ rays firmly identified, mutually concident γ -gated on γ -gated on Bo Cederwall AGATA Physics WS, Istanbul May 2010

92.94,96 Pd levels and the role of T=0 np interactions at N=Z Bo Cederwall AGATA Physics WS, Istanbul May Pd theo full np 92 Pd theo no np 92 Pd T=0 92 Pd T=1 96 Pd theo 96 Pd exp

96,98 Cd Shell model calculations by. Blomqvist, R. Liotta, C. Qi et al. Bo Cederwall AGATA Physics WS, Istanbul May 2010

Pd level systematics near N=Z Shell model calculations by J. Blomqvist, R. Liotta, C. Qi Bo Cederwall AGATA Physics WS, Istanbul May 2010

96,98 Cd level and the role of T=0 np interactions at N=Z 96 Cd theo full np 96 Cd theo no np 96 Cd T=0 96 Cd T=1 98 Cd theo 98 Cd Bo Cederwall AGATA Physics WS, Istanbul May 2010