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Probe the structure & spectroscopy at large isospin Measure unbound states  detection devices

Nuclear densities et excitations of exotic nuclei via direct reactions. ACTIVITIES AND PERSPECTIVES. Neutron-skin structure and shell evolution of weakly-bound neutron-rich SPIRAL / SPIRAL2 / EURISOL nuclei in coupled-reaction channel studies.

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Probe the structure & spectroscopy at large isospin Measure unbound states  detection devices

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  1. Nuclear densities et excitations of exotic nuclei via direct reactions ACTIVITIES AND PERSPECTIVES Neutron-skin structure and shell evolution of weakly-bound neutron-rich SPIRAL/SPIRAL2/EURISOL nuclei in coupled-reaction channel studies Structure studies at the drip-lines : exemples, + exp-theory GOAL: extension of systematics of neutron rms radius and of neutron excitation along isotopic chains n , p • Probe the structure & spectroscopy at large isospin • Measure unbound states  detection devices NEED FOR AN IMPROVED THEORETICAL FRAMEWORK OF STRUCTURE AND REACTIONS Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  2. Neutron skin halo 6He 8He 4He 4He Change in shell structure New magic numbers Local properties (N,Z) Neutron skins halo,clusters Nuclear structure towards the drip-lines : phenomena to explore & to understand Evolution of structure at large isospin ? Drip-lines: limit of nuclear binding, large isospin Exploration: new exotic structures  neutron-skin Tests: nuclear modelling & interactions VNN(Tz) Weakly bound states ? Continuum coupling ? Isospin dependence ? 2008: what do we know? 2016: future explorations Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  3. Nuclear landscape towards the drip-lines 2008 Nuclear landscape towards the drip-lines 31 F 24 O 8 23 N Z C 12 22 6 19 B 4 Be 14Be 4He Li 11Li 2 He p p d t 6He H 8He borromean n N 2 4 6 8 10 12 14 16 6He Testing ground Very few drip-line nuclei have their identity card complete  Masses, size, densities, neutron excitation, low-lying spectroscopy, shell structure Drip-line : 8He neutron-skin SPIRAL 8He (T1/2= 119ms) I= 104/s ; E=15.7 A.MeV reaction target CH2 Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  4. Shell structure far from the valley of stability halo and neutron-skin Experimental Devices Detector of Charged particles Si-strips, CsI x-y-E-DE-TOF 6He Z 8He Beam detector CATS-BTD SEDI-SPhN N MUST2 Collaboration: DAPNIA, GANIL and IPN-Orsay target 10 cm beam SPhN activities on structure of exotic nuclei via direct reactions • Objectives : • evolution of nuclear structure at large N/Z •  nuclear correlations, p-n interaction • exploration of new phenomena • - tests of the validity of the models Method : direct reactions induced by radioactive beams GANIL/SPIRAL ; SPIRAL2 in 2012 Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  5. Light nuclei and three-body forces S. Pieper et al. Nucl Phys. A751(2005), 516c PRC 70 (2004) 54325 Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  6. Structure of 8He extracted from direct reactions on proton target 8He(p,d) 8He(p,t)6He(0+) 8He(p,p) CRC calc 8He(p,t)6He(2+) SPIRAL 8He +p @ 15.7A.MeV F. Skaza PhD SPhN F. Skaza, N. Keeley, VL et al., PLB 619. 82 (’05) N. Keeley et al.,PLB 646,222(’07) Coupled-channel calc.: N. Keeley (SPhN) • Structure of ground state & search for unbound excited states •  spectroscopy of light charged particles p,d,t (MUST) •  measurements of resonances in 8He NPA 788c, 260 (’07) • angular distributions ; analysis in coupled reaction channels • PLB 619. 82 (’05) ; 646, 222 (’07) Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  7. Structure of 8He extracted from direct reactions on proton target 1p1/2 1p3/2 8He(p,d) 1s1/2 8He(p,t)6He(0+) p n 8He(p,t)6He(0+) RIKEN 61.3 A.MeV 1p1/2 8He(p,t)6He (2+) 1p3/2 1s1/2 8He(p,t)6He2+ p n CRC calc CRC calc Data: A. A.Korsheninnikov et al, PRL 90, 082501 (‘03) CRC Coupled-reaction channel analysis: N. Keeley (SPhN, Inst. A. Soltan) [1] 8He(p,d)7He C2S = 4.4 ± 1.3 [CCBAanalysis] CRC (p,p) (p,d) C2S = 3.3 ± 1.3 PLB 619, 82 (’05) [2] (p,t) wf. of 8He%6He [8He/6He(0+)] =1 ; [8He/6He(2+)] =0.014 Consistent with results from quasi-free scattering of 8He measured at GSI, LV Chulkov et al, NPA759, 43(’05) Data: SPIRAL-MUST [1] F. Skaza et al., PRC73, 044301(’07) [2] N. Keeley et al, PLB 646, 222(‘07) Configuration mixing : (p3/2)4 and (p3/2)2(p1/2)2 Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  8. Spectroscopy of 8He : exp versus theory 1p1/2 1p3/2 1s1/2 p n experiments theories (p,p’) [Kor93][0er95] [Nil95] [Boh99] [Mar01] COSMA model +4n M. Zhukov et al. PRC50, 1(‘94) [Kor93] A.A. Korsheninnikov et al., PLB 316 (‘93) 38 [Oer95] W von Oertzen et al., NPA588 (‘95) 129 [Nil95] T. Nilsson et al., NPA583 (‘95) 795 [Boh99] H.G. Bohlen et al., Prog. Part. Nucl. Phys. 42 (‘99) 17 [Mar01] K. Markenroth et al., NPA679 (‘01) 462 [Wir02] R.B. Wiringa & S.C Pieper, PRL 89 (‘02) 182501 [Nav04] P. Navratil & B.R. Barrett, PRC 57 (‘98) 3119 +private co. Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  9. Spectroscopy of 8He : exp versus theory SPIRAL (p,p’) E(MeV) Γ (MeV) 2+ 3.62 ± 0.14 0.3 ± 0.2 ? 5.4 ± 0.5 0.5 ± 0.3 experiments theories (p,p’) [Kor93][0er95] [Nil95] [Bohl99] [Mark01] And the specific treatment of resonant states ? Wigner : « Beautiful theories have to face ugly facts » Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  10. Spectroscopy of 8He : exp versus theory P. Navrátil & B. R. Barrett, PRC 57, 3119 (‘98). “The 8He nucleus is a weakly bound system, where scattering to the continuum will play an important role in the structure of higher-lying states.” Gamow Shell Model (GSM): consistent description of bound states and the particle continuum (resonances and the non-resonant scattering background). N. Michel et al., PRL 89, 042502 (‘02) PRC 67, 054311 (‘03) The gs is bound by CC correlations Continuum Shell Model (CSM): Discrete and Continuum Spectra in the Unified Shell Model Approach, A.Volya & V. Zelevinsky, PRL 94, 052501(‘05) [QMC] [NCSM] [GSM][CSM] Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  11. Conclusions conclusions ... prospectives n , p (p,p’) Rms (fm) 8He Proton Neutron Matter COSMA 5-body 1.69 2.74 2.52 HF+corr Sagawa 1.95 2.67 2.51 NCSM, Navrátil 2.00 2.59 2.46 NCSM NCSM (No Core Shell Model) (V3eff 4hw, 13MeV ) Alpha + 4 n COSMA: Alpha+4n Validation of no-core shell model calculations (NCSM) for gs (p,p’) mainly sensitive to the neutron excitation ; Transition densities 2+  0+ : NCSM calc. overestimate the p & n excitations No core Shell model Test of transition densities ; Analysis in progress CRC (p,p’) Coupling with the (p,t) Test of the validity of 8He gs densities using (p,p) : neutron-skin features close to NCSM densities COSMA not valid NEUTRON-SKIN THICKNESS: ~ 0.6 +/- 0.05 fm Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  12. Participants of the experiment8He(p,p’) SPIRAL E405S CEA-SACLAY DSM/DAPNIA/SPhN : N. Alamanos, F. Auger, A. Drouart, A. Gillibert, V. Lapoux, L. Nalpas, E. Pollacco, R. Raabe,J-L. Sida, F. SKAZA (PhD). IPN-Orsay : D. Beaumel, Y. Blumenfeld, F. Delaunay, E. Becheva, J-A. Scarpaci Ganil : L. Giot, P. Roussel-Chomaz FLNR - Dubna: S. Stepantsov, R. Wolski University of Ioannina: A. Pakou INTERPRETATION ANALYSIS : Microscopic densitiesP. Navrátil + interaction Argonne H. Sagawa HF +correlations Futur : cf M . Ploszajczak Ganil JLM potential: code Dietrich (Livermore) ; form factors (home made, VL) + CRC calc. N. KEELEY With the Fresco code (IJ Thompson, Surrey Univ). COLLABORATION MUST2 CEA DAPNIA, GANIL, IPN-Orsay • DAPNIASEDI E. Atkin, P. Baron, F. Druillole, F. Lugiez, B. Paul, M. Rouger ; • SPhN : A. Drouart, A. Gillibert, V. Lapoux, L. Nalpas, E. Pollacco • IPN-OrsaySED: P. Edelbruck, L Lavergne, L. Leterrier, A. Richard, M. Vilmay, E. Wanlin, • Structure Y. Blumenfeld, D. Beaumel, E. Becheva • GANIL GIP M. Boujrad, L. Olivier, B. Raine, F. Saillant M. Tripon, Physics P. Roussel Chomaz Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  13. Collaboration Structure & spectroscopy of exotic nuclei 6He low-lying spectroscopy via 8He(p,t)6He E525S DAPNIA/SPhN: N. Alamanos, F. Auger, A. Drouart, A. Gillibert, N. Keeley, V. Lapoux, X. Mougeot (TH), L. Nalpas, E. Pollacco, C. Simenel IPN-Orsay : D. Beaumel, Y. Blumenfeld, J. Guillot, J-A. Scarpaci Visiteurs à Orsay : H. Iwasaki, D. Suzuki GANIL : P. Roussel-Chomaz, C. Force, L. Gaudefroy, T. Kalanee,T. Roger A. Soltan, Varsovie : K. Rusek, I. Strojek FLNR - Dubna: R. Wolski University of Ioannina: A. Pakou, T. Mermizedakis Technical and software support: ASIC DAPNIA/SEDI E. Atkin, P. Baron, F. Druillole, F. Lugiez, B. Paul, M. Rouger Technical and software support: SPEG P. Gangnant, JF Libin Ganil, services techniques J. Cacitti, G. Fremont, C. Spitaels GIA ex GIP : C. Houaner, G. Leberthe, L. Légeard, L. Olivier, M. Tripon, B. Raine, F. Saillant Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  14. Nearfarfutureprojectsplans Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  15. MUST2 MUr àSTrips2, new generation of MUST 2004-6 collaboration : CEA-DAPNIA, GANIL, IPN-Orsay MUST2 • Developed by : • DAPNIA/SEDI : µ-electronics R&D ASIC • GANIL • IPN Orsay Increased compacity due to the ASIC technology (Application Specific Integrated Circuit)  coïncidencesparticle -  • MUST1  MUST2: improvments • factor 3 in active area • smaller volume of PAmp : x 6 • better time resolution Si(Li) 4.5 mm Exotic shapes and resonances Si strips 300 m 100 x 100 mm2 X, Y , T, E 128X 128Y One-particle state Spectroscopic factors DE collaboration MUST2: SPIRAL + Futur SPIRAL2 CsI 3 cm 4 x 4 segments Evolution of neutron excitation Mn vs Nalong isotopic chains 100 mm MUST2 MEASUREMENTS AND ANALYSIS OF REACTIONS IN COUPLED- CHANNELS Present techniques Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  16. Spectroscopy of 6He States between 2 and 10 MeV ? Positions 2+2, 0+2 VNN +VNNN  Correlations in light neutron-rich nuclei 0+2 8.54 1+ 6.50 5.79 2+2 0+ 6 1+ ~5 2+ 0+2 5 1+ 4.5 2.53 2+ 2+2 4.3 G (2+2) = 1.2 1.8 2+ 0+ 1.8 2+ 0+ Pieper et al. NN+NNN IL2 PRC70,054325(’04) Navratil et al. No Core shell Model 10hw V2eff 0+ Danilin et al. Few-Body model PRC 55, 577 (’97) THEORIES Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  17. CATS1 CATS2 Experimental set-up with MUST2 CH2 target 1mg/cm2 SISSI-SPIRAL Beams 8He, 20,22O, 14O I = 104 - 105 /s Identification A,Z : SPEG p,d,t MUST2 MUST2 @ d=15 cm 5-25 deg lab (15-80 c.m.) Sect. Eff (p,t) ~ 5 10-3 – 0.5 mb/sr CATS2 Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  18. Transfer reactions ; coupling between particle and gamma spectroscopy Beam tracking BTD CD2 p (d,pg) Gamma detection Identification : VAMOS Particle-spectroscopy (d,pg) Ex: MUST2-like array VAMOS (d,pg)A+1Z Structure of exotic nuclei via direct reactions Charged-particle spectroscopy Thin target CH2 ,CD2 1 mg/cm2 Complete kinematical reconstruction access to bound and unbound states I (> 5. 103/s) ex : SPIRAL2 96Kr @ 10MeV/n I= 104 /s 96Kr(d,p)97Kr, (d,d’) (d,t) EURISOL n-rich Ne, Ca, Ni, Kr, Sn @ 20-50MeV/n I > 105 /s AZ(d,p)A+1Z AZ Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  19. Nuclear landscape towards the drip-lines 2008 Nuclear landscape towards the drip-lines Next drip-line nuclei ? N 39 33 36 16 18 20 22 24 26 28 30 Testing ground 18 Z 07 : 125Pd (Z=46) found at RIBF 16 43Si 44Si 14 Low-lying resonances ? Neutron skin ? Neutron excitation ? Density Profiles ? New shell effects ? 34Mg 38Mg 40Mg 12 33Na 37Na 4He 10 30,31,32Ne 34Ne Tarasov97 Sakurai PLB448, (99) Notani PLB 542 (02), Lukyanov02 Tarasov PRC 75 (’07) 31F 8 24O structure of 24O ? Drip-line 23N  Complete the Identity card of drip-line nuclei 22C Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  20. Shell effects far away from stability with new generations of RIB s 20 8 neutrons stability neutrons drip-line N = 16, Z=8, 24O p3/2 fp 16 f7/2 p3/2 fp sd-fp f7/2 sd-fp d3/2 d3/2 N = 20 sd s1/2 sd N = 16 Z=14 30Si d5/2 s1/2 N = 16 d5/2 p1/2 N = 14 22O N = 8 p3/2 N = 8 N=16  Learnt from 1st generation of RIBs s1/2  RIBF,  SPIRAL2  EURISOL 82 Local properties (Z,N) N=34,40,70 instead of N=50,82 ? (f7/2) (1h11/2-)12 Extension of the systematics of neutron excitation along isotopic chains systematics of neutron excitations vs N Search for new magic numbers Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  21. EURISOL Z EURISOL N Spectroscopy of unbound states in neutron-rich beams close to the drip-lines Which beams ? We want to gain in exoticity Complete the (p,p’) chains O (24O), Ne + Mg, Si, S, Ar +spectroscopy of neutron-rich nuclei: around doubly magic Z=28, N=40,50 ; Z=50, N=82 around N=28, N=40 (possible new magic), N=50, N=70 (new) Examples :34Ne , 38Ne (if not unbound), 60-70Ca, 104Se (Z=34, N=70) If the beams are new (36Ne ? 60-68Ca ?) or rare at present (24O few/s at GANIL, RIKEN) with EURISOL : counting rates less or around 103-105 /s

  22. SPECTROSCOPY of bound and unbound states ? E (MeV) Sn Transfer (d,p) & (p,d) Elastic & Inelastic scattering (p,p’) (d,d’) Evolution of the shell structure () Neutron-skin structures Unbound states in neutron-rich nuclei via direct reactions Letter of Intent for SPIRAL2 o Single-particle structure o Nuclear pairing o Spectroscopy of very-neutron rich nuclei o Cluster studies o Direct reaction mechanisms o Applications to astrophysics  cf LOI r process nucleosynthesis Cf GENERAL LOI : Direct Reactions Studies of Exotic Nuclear Structure - Experimental conditions and requirements: BEAM, DETECTION, THEORY - SPECIFICITY LOI-16 unbound states in n-rich nuclei Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  23. Unbound states Sn e.g. Ni, 30Zn, 34Se, 36Kr, Sn Skin and halos Soft collective modes • Exc spectra, density distributions • via (p,p’) • - Shell structure, s.p states, J • via nucleon-transfer 5 Alpha-clusters states 4 3 (p,p’), (p,d) (p,t) (d,d’) (d,p) (d,t) 2 MeV 1 Exotic shapes and resonances 94-96Zn 94-96Kr 96-98Sr 134-136Sn Z One-particle state Spectroscopic factors Prospectives Evolution of neutron excitation Mn vs Nalong isotopic chains 2012+ 2020+ Beams Variety A,Z Limit of nuclear binding, I  SPIRAL2 EURISOL N Going closer to driplines with higher intensities : opened physics fields Far ..far away Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  24. neutrons (g7/2) (1g9/2)10 (2p1/2) (1f5/2) S2n S2n 8 8.03# 8.02# E (MeV) 2+ , 4+, 6+ ? ? ? Sn 5.06# ? 4 6+ ? 2.97# Sn Sn 2.96# 4+ ? 2 2+ ? 1/2(-) (7/2-) ? 0 gs 0+ 0 0.78s 50 94Kr(d,p) 95Kr 95Kr(d,p) 96Kr 96Kr(d,p) 97Kr Low-lying spectroscopy of n-rich Kr isotopes Neutron excitation of 96Kr via (p,p’) and shell structure of 97Kr via 96Kr(d,p) Bound and unbound states  full reconstruction of the kinematics  (p,p’) or (d,p) excitation spectrum +Spectroscopic factors ISPIRAL2 94Kr I > 109 0.75 MeV 95Kr I > 9. 108 2.84 MeV 96Kr I > 104 0.74 MeV Q-value Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  25. LOI “Unbound states” Homework for the 2007-2012 period CD2target -ray detector exotic beam SPIRAL2 AZ identification p EXOTIC beam tracking devices A+1Z particle detection SP2 Beams : larger incident energies required (cf L window & access to excited states) PREPARATION OF THE THEORETICAL FRAMEWORK • Coupled-reaction channel analysis: • - treatment of direct reactions for structure embedded in the continuum • proton-nucleus, deuteron-nucleus optical potentials • Microscopic form factors for (p,p’) reactions • Study of benchmark reactions PREPARATION OF THE EXPERIMENTAL SET-UP BTD+particle-gamma coupling+ Detection at the focal plane for(Z,A) identification • separation of excited states • with high-density level • cf LOI-direct Reactions • Future 4 GASPARD array • GAmma Spectroscopy • & PArticle Detection • simulation of exp set-up Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  26. Collaboration LOI SPIRAL2 “Unbound states” CEA-SACLAY DSM/DAPNIA/SPhN: N. Alamanos, F.Auger, R.Dayras, A. Drouart, A. Gillibert, N. Keeley, V. Lapoux, L. Nalpas, E. Pollacco, C. Simenel, X. Mougeot. IPN-Orsay : D. Beaumel, S. Fortier, F. Hammache, E. Khan, C. Petrache GANIL: L. Gaudefroy, W. Mittig, F. de Oliveira, P. Roussel-Chomaz, H. Savajols, O. Sorlin HMI Berlin, Germany: H.G. Bohlen, Tz. Kokolova, W. Von Oertzen, C. Wheldon JINR, FLNR Dubna, Russia: A. Fomichev, M.S. Golovkov , A. Rodin, S. Sidorchuk, S. Stepantsov, G. Ter-Akopian, R. Wolski IKS University of Leuven, Belgium: R. Raabe IPHC Université Louis Pasteur, Strasbourg: Ch. Beck, S. Courtin, A. Khouaja INFN-Catania, Italy: A. Musumarra KVI, Netherlands: M.N. Harakeh, H.G. Wortche Florida State University, US: K.Kemper University of Huelva, Spain: I. Martel University of Ioannina, Greece:: T.J. Merzimekis, A. Pakou, D. Roubos University of Santiago de Compostela, Spain: M.D Cortina-Gil Theoretical support : CEA-Bruyères-le-Châtel DAM/DIF/SPN: E. Bauge, P. Chau Huu-Tai, J.P. Delaroche, H. Goutte, S.Péru CENBG: M. Bender IPN-Lyon: K. Bennaceur IST, Lisboa, Portugal: R. Crespo The A. Soltan Institute for Nuclear Studies, Hoza, Warsaw, Poland: K. Rusek NSCL, MSU, USA: T. Duguet University of Pisa-INFN-Pisa: G. Blanchon, A. Bonnacorso The Open University, UK:R.S. Mackintosh University of Sevilla, Spain: A.M. Moro VAEC Hanoï, Vietnam: Dao. T. Khoa; INST Hanoï: Hoang S. Than Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  27. ANALYSIS OF (D,P) CROSS SECTIONS... Ex : N. Timofeyuk & RC Johnson, PRC 59, 1545 (‘ 99) : d break-up included within the adiabatic approach from Johnson & Soper Analysis of the 16O(d,p)17O,10Be(d,p)11Be, and 11Be(p,d)10Be reactions. Comprehensive analysis method for (d,p) stripping reactions ; test calc. : 12C(d,p)@ 25 MeV10Be(d, p) @ 12 and 25 MeV , N. Keeley,* N. Alamanos, and V. L, PRC 69, 064604 (‘04) MEASURE ELASTIC SCATTERING to estimate coupling effects (virtual coupling potential related to excited states, compound nucleus effects… needed for coupling scheme … MEASURE INELASTIC SCATTERING (d,d ’) (p,p ’) Once upon a time… Successful analysis for the stable nuclei [cf 40Ca(d,p) ]: E=7, 8, 9,10, 11, 12 MeV Lee,..Schiffer, Satchler, Drisko, PR136 4B (’64)40Ca(d,p) 41Ca a test of the validity of the DWBA R. Satchler Direct nuclear reactions,Clarendon Press, Oxford Univ Press 1983 « The DWBA was shown to be inappropriate for the analysis of (d, p) reactions some 30 years ago, due to the importance of the deuteron breakup channel. » We know that average properties & parameterizations are working for stable beams (~300 species) ONLY SMALL PART of all 2000 RIB, even more 3000 possible ones … DO THE BEST POSSIBLE CALCULATIONS !!!! DWBA is a limited framework, turns out to be WRONG for strongly-coupled channels cf CRC calculations, CDCC: Nick Keeley’s lecture at ECOLE JOLIOT-CURIE ’07 les réactions nucléaires comme sonde de la structure Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  28. Accurate data covering a largeangular domain • Elastic : entrance OM potential under control (p,p) • Check role of continuum coupling • Sensitivity to the detailed structure of exotic nuclei, • Test unusual shape +unbound states • Compare to models (SM, HFB, BCS+QRPA, AMD) EURISOL : a new theoretical framework Probe for the structure : (p,p’) But flux shared between several reaction channels  elastic and transfer reactions + competition between main reaction channels NEED TO DEFINE THE APPROPRIATE SCATTERING THEORY State of the art : Coupled reaction channel analysis  explicit channel coupling +Microscopic potentials FUTURE: Structure and reaction on the same footing Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  29. Strong pickup-coupling effect on p+11Be elastic scattering N. Keeley and V. L PRC 77, 014605(‘08) CRC calc :11Be(p,d)10Be* pickup to the 5.960 MeV 1- and 6.263 MeV 2- doublet of excited states in 10Be EURISOL : a new theoretical framework Data+ Virtual coupling potential for elastic scattering of 10,11Be on p V. L et al.,PLB 658, 198 (’08) Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  30. Drip-line studies Drip-lines : limit of nuclear binding, large isospin Exploration : new structures of exotic nuclei Tests : nuclear modelling & interactions VNN(Tz) n , p SPIRAL2, RIBF, EURISOL FIND NEW REGIONS OF INTEREST  Nuclei with large matter extension (neutron-skin, superdeformation…)  New shell gaps • EXTENSION OF the systematics of neutron excitation along isotopic chains • MEANS to Probe the structure & spectroscopy at large isospin • Measure unbound states •  EXPLORATION: Spectroscopy of low-lying resonances, unbound states, neutron excitation, exotic excitation modes soft dipole resonance and transition densities Halo,skin features of weakly-bound exotic nuclei local shell change : like N=16 (34, 70..) indicated by Ex(2+), B(E2) S2n, and evolution ofneutron excitation SIMPLE PROBE : (p,p’) combined to Coulex information direct reactions in inverse kinematics, missing mass method Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  31. spectroscopy of low-lying states of neutron-rich isotopes via (p,p’), (p,d) (p,t), (d,p) 40c.m. 20c.m. 10c.m. 34Ne+p @ 25 A.MeV  t d p FUTURE WORKS Improvment of exp set-up + Theoretical framework Present (1st generation) intensities : few part/s Needed : (at least) 103-105 /s • Measurement to unbound states: • Particle-spectroscopy • Large enough intensities  EURISOL • Large angular coverage all reactions measured simultaneously • Elastic and transfer • Low particle threshold :small c.m. angles • Possible to carry out full coupled-reaction channel analysis • EXTRACT form factors from (p,p’) • spectroscopic factors from (d,p) suitable range of beam energies for (p,p’) and (d,p) : E ~ 10-30 MeV/n In 2016+: new beams of neutron-rich Ne, Ca, Ni, Kr, Sn isotopes…  Access to neutron-thickness evolution + change in shell structure Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  32. Theoretical framework for the analysis of direct reactions Improved approach (best we can do today) COMPLEX MICROSCOPIC POTENTIALS  to test the validity of nuclear density FORMALISM in COUPLED REACTION CHANNELS  To include the coupling to excitations AND to reaction channels PROTOTYPE-STUDY: 8He(p,p’) & (p,d) : PLB 619, 82(’05) Usual framework: DWBA, not valid, need to operate with CRC The usual ingredients and models based on past studies for stable nuclei must be put into question A PRIORI How good (potential, framework) is really good for exotic beams ? Validity of optical potentials ? Examine the assumptions in the case of weakly-bound nuclei or for specific coupling (large spectroscopic factors, enhanced excitation etc..) To be checked by measuringcarefully the elastic scattering, TESTING GROUND FOR THE INTERACTION POTENTIAL AND THE REACTION MODEL • Enhanced effects in the case of weakly-bound exotic nuclei: • Coupling to continuum, 3-body, many-body correlations • Shell structure embedded in the continuum • Use the predictions of improved structure theories to take into account these effects and the isospin-dependence of the nuclear interaction To be scheduled in 2008 ESNT Workshop STRUCTURE AND REACTIONS IN COUPLED REACTION CHANNELS Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  33. Structure and spectroscopy of exotic nuclei via direct reactions ? E (MeV) Sn () theorist Experimen- talist • GOALS • find new aspects de structure • weakly-bound exotic nuclei, • new constraints for the nuclear models of structure and reaction • modelling of strong interaction in the nucleus for extreme isospin cases • test bench for the unification of the future models for structure and reaction with explicit contribution of the coupling effects observable Nuclear Models Structure Bound states Reactions Scattering states Role of the coupling to the continuum PCV Effective interaction NN Isospin dependence Beyond mean-field role of many-body correlations pairing Role of coupling to continuum Conclusions Perspectives Powerful tool for the study of unbound states : DIRECT REACTIONS IN COUPLED CHANNELS MUST2 PHYSICS OF THE PUZZLE AND OF THE INTERPLAY « MOSAÏQUE DES NOYAUX », P. BONCHE, CEA-SPhT Studies of exotic nuclei need to combine several probes & Require systematics along extended isotopic chains Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  34. Discussions - Questions the force ? « On the theoretical side, we are lacking a derivation of the nuclear force that is based upon theory (in the true sense of the word) and produces a quantitative NN potential » R. Machleidt and I. Slaus, The nucleon-nucleon interaction, TOPICAL REVIEW J. Phys. G : Nucl. Part. Phys. 27 (2001) R69-R108 sp states + Couplings + collective degrees of freedom ? « In all the recent works devoted to the single-particle states the particle-vibration coupling is mentioned but not taken into account so far within the same framework. A serious step forward in this direction has to be made. » W. Zou, G. Col`o, Z. Ma, H. Sagawa and PF Bortignon, Tensor correlations and evolution of single-particle energies in medium-mass nuclei, Phys. Rev. C 77, 014314(2008) Reaction +structure? Revisit scattering theory? Treatment of the structure embedded in the continuum, of the unbound states ? Extended framework treating on the same footing bound and scattering states ? Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  35. scattering states STRUCTURE ? INTERACTION ? V(r), r (r) N N bound states Reactions involving states close to continuum ? Open questions Structure theories for states embedded in the continuum ? We need theories with structure and reaction embedded in the continuum Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  36. Conclusions conclusions ... prospectives Ocean of weakly binding energies Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  37. Compléments (I) Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  38. Explore Shell quenching Nuclear structure ? Which interactions ? How to model? p n   n p Z N VNN +VNNN : S. Pieper, Wiringa et al continuum-coupling (CC)effects: K. Bennaceur, M. Ploszajczak, …. A.Volya et al. Density-dependent pairing effects, DFT : T. Duguet et al. T. Otsuka et al Nuclear potential ; nuclei at larger N/Z  weaker binding energy  more diffuse nuclear potential (J. Dobaczewskiet al.  isospin-dependent terms, p-n tensor interaction  enhanced nuclear correlations, CC effects  change of SO potential (B. Todd-Rutel et al.) Theoretical challenges: Interplay between these effects Structure of exotic nuclei Rules of the evolution of nuclear structure at large isospin ?  Experimental exploration Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  39. 31 F O RMF 24 8 N 23 12 Z C 6 19 B 4 Be 14Be Li 4He 11Li 2 He p p d t H 6He borromean HFB-Gogny 8He HFB-Skyrme n N 2 4 6 8 10 12 14 16 Predictions of the Drip-lines Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  40. Predictions of the drip-lines, HFB-Skyrme Ni isotopes Kr isotopes microscopic predictions forS2n energy and deformation throughout the mass table Density functional method + Sly4 Skyrme NN interaction J. Dobaczewski et al. M.V. Stoitsov, et al., PRC68, 054312 (‘03) Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  41. Reference : calc from PRC[Stoit03] Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  42. Unbound states of exotic nuclei S2n=8.5 ? Sn= 5.2 1.52 4+ 2+ 0.67 MeV 0+ 94Kr S2n=7.91 2+ ? 6? MeV Sn= 4.95 0+ 96Kr Similar trend for neutron-rich SPIRAL2 beams : few bound states Calc : M.V. Stoitsov, et al., Phys. Rev. C68, 054312 (‘03) Data AME2003 Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  43. Predictions of the Drip-lines, HFB-Gogny M. Girod et al, CEA-DAM Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  44. Predictions of the Drip-lines, RMF 125Pd (Z=46) found at RIBF, N=79 Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  45. Compléments (II) Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  46. Nuclear structure explored via elastic and inelastic scattering (p,p’) n, p exploring… 2+ 0+ proton densities & excitation  EM probe (p,p’) probe : sensitive to densities, excitation of neutrons & protons Mn, Mp Stable nuclei : (e,e’) probe Radioactive beams : no direct access to protons but to integrated value B(E2)from Coulex Microscopic potential nucleus- nucleon U(rho,E) Ex : local microscopic complex potential JLM, J.P. Jeukenne, A. Lejeune & C. Mahaux, PRC 16 (‘77) 80 valid for Ep, En up to 160 MeV DENSITIES U(,E) = vV (,E)+i wW(,E) drtr =<i|(r-r’)|f> B(E2;,if)=|Mp|2/(2Ji+1) y gs gs Testing ground : weakly-bound light nuclei Weakly bound states ? Continuum coupling ? Isospin dependence ? Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  47. Search for low-lying resonances and study of neutron excitations S2n = 0.975 beam MUST (8 in a wall) + CATS 2+ 1.8 MeV 0+ 6He Present techniques & results (p,p’) probe Particle spectroscopy structure studies by (p,p’) & (p,d) reactions using GANIL/SISSI or SPIRAL beams and MUST+CATS Elastic scattering sensitive to the matter rms Inelastic scattering : sensitive to the shape of the density Nuclear densities, neutron excitation C.Jouanne, VL. et al., 10,11C(p,p’) PRC 72, 014308 (’05) rmsm (10C) : 2.42 0.1 fm ; rmsm (11C) : 2.33 0.1 fm [rmsm (12C) : 2.30 (3) fm] Weakly-bound nuclei Unbound excited states low-lying resonances exotic He isotopes MUST : Y.Blumenfeld et al., NIM A421, 421 (‘99) CATS : S. Ottini et al., NIM A431, 476 (‘99). Halo, Neutron-skin structure Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  48. Prototype of (p,p’) & direct reactions at low energy: 8He(p,p’) CsI 1.5 cm Si (Li) 3mm Si Strips 300 m X, Y, T, E wave fct 8He MUST neutron-skin ? Resonances ? 3.6 MeV 2+ p S4n=3.1 Si Strip 6 x6 cm2 SPIRAL 8He @ 15.7 A.MeV 14000 /s [1ary beam: 13C @ 75 A.MeV] Sn =2.5 S2n = 2.1 He CH2 target 0+ 8He Beam detector CATS2 CATS1 T1/2 =119 ms 8He (T1/2= 119ms) I= 104/s reaction target CH2 set-up at GANIL PROBE : 8He(p,p’)8He*  test of the validity of the densities eg 6He(p,p’) @ 40.9 MeV/n GANIL-MUST A. Lagoyannis et al., PLB 518, 27 (‘01) 2n-Halo features 6He NPA722, 49c(‘03) Collaboration : SPhN, GANIL, IPN-Orsay, FLNR-Dubna, Univ. Ioannina (Greece) Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  49. 1p1/2 1p3/2 1s1/2 p n COSMA SAGAWA p n V3eff 4ħω ħΩ=13 MeV Structure of 8He models B(E2) = 0.25e²fm4 Mn/Mp = 13.5 COSMA: M.V. Zhukov, A.A Korsheninnikov & M.H Smedberg, PRC 50 (‘94) R1 H. Sagawa, PLB 286 (‘92) 7 P. Navratil & W.E. Ormand, PRL88, 152502 (‘02) priv. Co. Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

  50. 8He(p,p’) a new resonance  Structure models overestimate Eexc for unbound excited states  Understanding of the weakly bound & unbound states requires calculations including the continuum coupling 8He(p,d)7He transfert 1n Resonant states of7He Indication of a possible 1/2-resonanceat low energy PRC73, 044301(’06) 1p1/2 1p3/2 E(MeV) Γ (MeV) 1s1/2 NP A788, 260 (2007) p n 2+ 3.62 ± 0.14 0.3 (2) ? 5.4 ± 0.5 0.5 (3) l=0 l=2 Coupling to the (p,d) channel to understand the (p,p) PLB 619, 82(’05) 8He(p,d)7HeC2S = 4.4 ± 1.3 mixing : (p3/2)4 + (p3/2)2 (p1/2)2 8He2+ p 7He d PLB 646, 222(’07) p 8He Conclusions: structure and spectroscopy of 8He (p,p’) (p,d) (p,t) @ 15.7 A.MeV SPIRAL 8He(p,p’) E* : 2 states All direct reactions at the same energy : a need for a complete coupled-channel analysis Direct reactions to unbound statesESNT 4-6Fev. 08 CEA-SPhN vlapoux@cea.fr

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