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Physics LOI for NEDA

Physics LOI for NEDA. R. Wadsworth University of York , G. de Angelis INFN LNL. Istanbul 19 june 2009. Defining the Physics. Nuclear Astrophysics Element abundances in the Inhomogeneous Bib Bang Model (Weizmann, Soreq, GANIL, York collaboration)

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Physics LOI for NEDA

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  1. Physics LOI for NEDA R. Wadsworth University of York , G. de Angelis INFN LNL Istanbul 19 june 2009

  2. Defining the Physics • Nuclear Astrophysics • Element abundances in the Inhomogeneous Bib Bang Model (Weizmann, Soreq, GANIL, York collaboration) • Isospin effects on the symmetry energy and stellar collaps • Nuclear Reactions • Level densities of neutron rich nuclei (Naples, Bordeaux, Debrecen, LNL, Florence collaboration) • Fission dynamics of neutron-rich intermediate fissility systems • Nuclear Structure • Probe of the T=0 correlations in N=Z nuclei: The structure of 92Pd • Coulomb Energy Differences in isobaric multiplets: T=0 versus T=1 states • Coulomb Energy Differences and Nuclear Shapes • Low-lying collective modes in proton rich nuclei

  3. Reaction Paths in Nuclear Astrophysics rapid proton capture, Nuclear Astrophysics : • Element abundances in the Inhomogeneous Bib Bang Model • (Weizmann, Soreq, GANIL, York collaboration)

  4. Letter of Intent for the proposed “Neutron Wall” at SPIRAL-II Measurement of the 8Li(a,n) 11B Reaction Michael Hass for the Weizmann-Soreq-GANIL-York collaboration We propose to study the 4He(8Li,n)11B reaction using 8Li beams at SPIRAL-II. The R&D efforts to produce unsurpassed intense beams of 8Li at SPIRAL-II may result in 8Li very well becoming one of the first radioactive beams to be used at SPIRAL-II. This fact, together with the unique performance of the proposed neutron wall and of other ancillary charge-particle detectors will provide an ideal experimental setup for such studies. The data thus obtained should clarify the poorly known cross section for this reaction, which is important for several scenarios in the field of explosive nucleo-synthesis. Michael Hass - 8Li(a,n)11B

  5. Fig. 2 States in 12B that are in the region of interest for cosmological (and stellar) environment(s) at temperatures of ~ 1 GK Fig. 1 Experimental data available in the literature Michael Hass - 8Li(a,n)11B

  6. 11B • Under current R&D: • Diffusion and effusion in the material • Ionization and extraction • Choice of ion source Expected Yields for a BeO target: SARAF (40 MeV, 2 mA): 8∙1012[6He/sec] SPIRAL2 (40 MeV, 5 mA): 2∙1013[6He/sec] Expected Yields for a BN target: SARAF (40 MeV, 2 mA): 2∙1012[8Li/sec] SPIRAL2 (40 MeV, 5 mA): 5∙1012[8Li/sec] Michael Hass - 8Li(a,n)11B

  7. Neutron (energy) + charge particle detections • Issues for consideration • 8Li@SPIRALII • The present scheme • uses the 11B(n,a)8Li reaction with • secondary neutrons from the initial • 5 mA, 40 MeV d beam with a porous • BN target. • Post-acceleration. Energy degrader. • The neutron wall • Charge particle (11B) detection Fig. 3 The proposed experimental setup. Michael Hass - 8Li(a,n)11B

  8. Isospin effects on the symmetry energy and stellar collaps Why is it important to study the symmetry energy ? (Naples, Debrecen, LNL, Florence collaboration) • Esym=bsym(T)(N-Z)2/A • As a part of the nuclear Equation Of State it may influence the mechanism of Supernova explosion • General theoretical agreement on its temperature dependence (LRT+QRPA vs. large scale SMMC) • Possible consequences of T dependence of Esym on core-collapse Supernova events • Effects enhanced by the instrinsic isospin dependence of Esym Fusion-evaporation reactions: Esym affects the particle B.E.

  9. SYMMETRY ENERGY Framework: Dynamical Shell Model Hartree-Fock Coupling single particle states to suface vibrations Nucleon effective mass mw(T) 0 < T < 3 MeV - 98Mo, 64Zn, 64Ni -LRT – QRPA Decrease of the effective mass  Increase of Esym Esym(T)= bsym(T) x (N-Z)2/A bsym(T)=bsym(0)+(h2ko2m/6mk)[mw(T)-1 –mw(0)-1] mw(T)=m + [mw(0) – m]exp(-T/To)

  10. Isospin effects on the symmetry energy Study with RIB’s from SPIRAL2 105Zr + 4He  109Mo 109Mo Ex=16 MeV 1n channel The isospin effects are larger than those due to the change of level density parameter a from A/8 to A/10. A strong sensitivity on isospin is also expected for the ER yields. (Same observables and experimental setup) Neutron energy and multiplicity information + Charged particle information + gamma ray information

  11. Nuclear Reaction Mechanisms: Evaporative neutron emission as a probe for the level density of hot neutron-rich compound nuclei(Naples, Bordeaux, Debrecen, LNL, Florence collaboration) Neutron energy and multiplicity information + Charged particle information + gamma ray information

  12. Why is it important to study the level density ? Level density is a basic ingredient for x-section calculations Astrophysical processes“Astrophysical Reaction Rates from Statistical Model Calculations”, ADNDT 75 (2000) 1-351 SHE’s production Capture of two nuclei in the attractive potential pocket. Probability of forming a compact compound nucleus (CN). Survival probability against fission. Evaporative process: Statistical Model

  13. Form A: Form B: Form C: Isospin effects on the level density parameter a Form C provides the best reproduction of experimental level densities 20<A<110 ENSDF Strong reduction of level density for exotic nuclei

  14. Isospin effects on the level density parameter a Study with RIB’s from SPIRAL2 • Observables • - s(xn channels) • n en. spectra • - ER yields n 84Ge + 4He n 134Sn + 4He A strong sensitivity on isospin is also expected for the evaporation residue yields Experimental setup: NEDA coupled to the gamma ray spectrometers EXOGAM or AGATA and/or the spectrometer VAMOS. (NEDA: TOF Measurements 3% resolution, energy threshold  1 MeV). Lcp could be also measured by Diamant.

  15. Fission dynamics of neutron-rich intermediate fissility systems (under study) Open questions in fission dynamics: Fission delay, nature of dissipation (one or two body) and its dependence on temperature and nuclear deformation Systems of intermediate fissility (A  150): possibility to measure observables in both fission and evaporation residue channels Measurements on nuclei with the same Z and different isospin allow to Study of the role of isospin in fission dynamics: Preliminary results from a dynamical model based on three dimensional Langevin equations 230 MeV 32S +92Mo Lcrit = 74  750 MeV 118Pd + 26Mg Lcrit =81  Ex122 MeV Experimental setup: NEDA coupled to fission fragment detectors

  16. Nuclear Structure : N=Z nuclei • Probe of the T=0 correlations in N=Z nuclei: • The structure of 92Pd • Coulomb Energy Differences in isobaric multiplets: • T=0 versus T=1 states • Coulomb Energy Differences and Nuclear Shapes • Low-lying collective modes in proton rich nuclei

  17. Probe of the T=0 correlations in N=Z nuclei: The structure of 92Pd (LNL, Stockholm, York collaboration) Neutron multiplicity information + charged particle + gamma ray information

  18. 56Ni (108pps) + 40Ca 92Pd (1 mb), 94Ag (1 mb)

  19. Coulomb Energy differences in isobaric multiplets: T=0 versus T=1 states (Sofia, Padova, York, Ganil, LNL collaboration) Neutron multiplicity ( and energy) information + Charged particle + gamma ray informations

  20. Example: Electromagnetic Transition Probabilities If Isospin Symmetry is valid: E1 (T=0) transitions in N=Z nuclei are forbidden E1 transition in mirror pairs have identical strength (higher sensitivity due to interference) Crucial Probe of the isospin symmetry and of its validity with increasing A and Z

  21. 64 32 32 64Ge Dobaczewski and Hamamoto Phys. Lett. B345 181 (1995) Electromagnetic Transition Probabilities Observation of a forbidden E1 transition in 64Ge forbidden E1? EUROBALL IV + Plunger experiment E. Farnea et al. Phys. Lett. 551B, 56 (2003) 32S+40Ca 125 MeV

  22. Isospin Mixing in Mirror Pairs 1) Charge invariance of the nuclear interaction In the validity of isospin symmetry 2) Long-wavelength approximation B(E1) strengths are identical in T=1/2 mirror pairs • Isospin mixing via the IVGMR provides an induced isoscalar component • In mirror T=0 transitions • Isovector terms have opposite sign • Isoscalar terms have equal sign B(E1) = BIS(E1) – BIV(E1) B(E1) = BIS(E1) + BIV(E1) J. Ekman et al. PRL 92, 132502 (2004)

  23. Electronic timing measurements 67Se 67As

  24. N=Z nuclei: Reactions with RIBS • 34Ar + 40Ca (105-120 MeV) • 69Br + p 1 mb • 71Kr + 2pn 5 mb • 68Br + pn 0.2 mb • 72Rb + pn 0.1 mb • How do we study the proton unbound cases e.g. 68,69Br? • 58Cu + 28Si (~200 MeV) • 81Nb + n 0.1 mb • 56Ni + 28Si (~200MeV) • 79Zr + n 0.2 mb

  25. Coulomb Energy Differences and Nuclear Shapes (York, LNL, Padova, Sofia collaboration) Neutron multiplicity information, charged particle and gamma information

  26. N=Z nuclei: Reactions with RIBS • 34Ar, 30S + 40Ca (105-120 MeV) • 69Br, 65As + p 1 mb • 71Kr, 67Se + 2pn 5 mb • 68Br, 64As + pn 0.2 mb • 72Rb, 68Br + pn 0.1 mb • How do we study the proton unbound cases e.g. 68,69Br? • 58Cu + 28Si (~200 MeV) • 81Nb + n 0.1 mb • 56Ni + 28Si (~200MeV) • 79Zr + n 0.2 mb A=64, 68 T=1 triplet

  27. Nuclear Structure : Low-lying collective modes in proton rich nuclei Valencia, INFN LNL , Paris, INFN MI collaboration. Neutron multiplicity (and energy), charged particle and High energy gamma information

  28. 34Ar + 16O 44Cr + 2n 34Ar108 pps

  29. Dipole Excitations towards the Proton Drip-Line CENTROID ENERGY OF THE LOW-LYING STRENGTH LOW-LYING TRANSITION STRENGTH B(E1) PROTON PYGMY DIPOLE RESONANCE Paar, Vretenar, Ring, Phys. Rev. Lett. 94, 182501 (2005)

  30. Dipole Excitations towards the Proton Drip-Line CENTROID ENERGY OF THE LOW-LYING STRENGTH 24Mg(p,p2n) 22Mg 22Mg + 16O 32Ar + 2n 22Mg108 pps LOW-LYING TRANSITION STRENGTH B(E1) PROTON PYGMY DIPOLE RESONANCE Paar, Vretenar, Ring, Phys. Rev. Lett. 94, 182501 (2005)

  31. Thanks for attention • Present LOIs still under development • Please join LOIs or present new ones • Upgrading of the physics case is on the way • Definition of the “day one” experiments

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