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The Pygmy Dipole Resonance – status and new developments

The Pygmy Dipole Resonance – status and new developments. From Giants to Pygmies – a short history Electromagnetic and hadronic interaction : Methods and experimental status Open questions and new experiments. Andreas Zilges University of Cologne.

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The Pygmy Dipole Resonance – status and new developments

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  1. The Pygmy Dipole Resonance – statusandnewdevelopments • FromGiantstoPygmies – a shorthistory • Electromagneticandhadronicinteraction:Methodsand experimental status • Open questionsandnewexperiments Andreas ZilgesUniversity of Cologne 11th International Spring Seminar  in honorof Aldo Covello  Ischia, May 2014

  2. Dipole responseofatomicnuclei Ex [MeV] 5 10 15 E1 PYGMY GDR OCTUPOLECOUPLING Strength (a.u.)  N. PietrallaR. Schwengner 2QP Strength (a.u.) GAMOWTELLER M1 Ex [MeV] 5 10 15

  3. Giant Dipole Resonance (GDR) 1937: Z. Phys. 106 (1937) 236

  4. 75 yearsago 1938: ... nature141 (1938) 326

  5. Giant Dipole Resonance (GDR) 1937: Z. Phys. 106 (1937) 236 1944: J. Phys. (USSR) 8 (1944) 331

  6. Giant Dipole Resonance (GDR) 1947: Photo-Fission in Uranium Phys. Rev. 71 (1947) 3

  7. Giant Dipole Resonance (GDR) PDR GDR Ex = 31 A-1/3 + 21 A-1/6 about 100%of EWSR Strength (a.u.) 5 10 15 Energy [MeV]

  8. Pygmy Dipole Resonance (PDR) 1961: Ann. Rev. Nucl. Sci. 11 (1961) 259

  9. Pygmy Dipole Resonance (PDR) 1961: Ann. Rev. Nucl. Sci. 11 (1961) 259 1969: Can. J. Phys. 47 (1969) 2850

  10. Pygmy Dipole Resonance (PDR) 1971: R. Mohan, M. Danos, and L.C. Biedenharn,Phys. Rev. C 3 (1971) 1740 Z protons, Z neutrons, N-Z excessneutrons

  11. Pygmy Dipole Resonance (PDR) 2002: Phys. Lett. B 542 (2002) 43 (g,g‘)

  12. Fromgiantstopygmies PDR GDR about 100%of EWSR 1-5%of EWSR Strength (a.u.) 5 10 15 Energy [MeV]

  13. Fromgiantstopygmies PDR GDR Strength (a.u.) 5 10 15 Energy [MeV]

  14. Relevanceoflow-lying E1 strength • PDR as a universal „collective“ excitationmode • Connection toneutronskin, neutronstarradius • Slopeofsymmetryenergy in EoS • Impact on nucleosynthesis P.-G. Reinhard and W. Nazarewicz, PRC 81 (2010) 051303(R) J. Piekarewicz et al., PRC 85 (2012) 041302(R) J. Erler et al., PRC 87 (2013) 044320 A. Carbone et al. PRC 81 (2010) 041301(R) B.A. Brown and A. Schwenk, PRC 89 (2014) 011307(R) S. Goriely, PLB 436 (1998) 10 E. Litvinova et al., NPA 823 (2009) 26

  15. Study ofthe E1 strengthdistribution via electromagneticinteraction (g,g‘) (g,n) Sn Strength (a.u.) 5 10 15 Ex [MeV] The photonscanbe real orvirtual!

  16. Scatteringof real photons (g,g‘) • Eg = 0 - Sn • veryselectiveexcitation (DJ=1 or 2) • energyresolutionDE=5-10 keV • complexsensitivitylimit • onlystablenucleicanbestudied (g,g‘) S-DALINAC@TUDELBE@HZDR HIGS@DUKE ELI@Bukarest rawspectrum! Counts D. Savran et al., PRC 84 (2011) 024326 Energy [keV]

  17. E1 distribution in stablenuclei: (g,g‘) S-DALINAC ELBE 89Y N. Benouaret et al., PRC 79 (2009) 014303 D. Savran et al., PRC 84 (2011) 024326 S. Volz et al., NPA 779 (2006) 1 A. Zilges et al., PLB 542(2002) 43

  18. Scatteringofvirtualphotons via (p,p‘) at 0° • Ex = 0 – 25 MeV • energyresolutionDE=25 keV • lessselective, complexdisentanglement • onlystablenucleicanbestudied 208Pb GRAND RAIDEN@RCNP A. Tamii et al., PRL 107 (2011) 062502

  19. Coulomb interaction in inverse kinematics • Ecm = few 100 MeV/A • radioactivenucleicanbestudied • energyresolutionDE=500 keV • complexdataevaluation LAND@FRS@GSINeuLAND@R3B@FAIR … gtalkbyO. Wieland P. Adrich et al., PRL 95 (2005) 132501

  20. Summed B(E1) strengthofPygmy Dipole Resonance D. Savran, T. Aumann, andA. Zilges, PPNP 70 (2013) 210

  21. Parametrizationof „exoticity“ DCCF=(S2p – S2n)/2 + EC [MeV] 208Pb 140Ce 68Ni 132Sn 48Ca chartofnuclidesfrom: P.D. Cottle, nature465 (2010) 430

  22. PDR vs. Coulomb correctedFermyenergy Non-consistentdatasets! D. Savran, T. Aumann, andA. Zilges, PPNP 70 (2013) 210

  23. PDR or GDR ? • Electromagneticprobesyieldmainlydistributionof E1 strength (and– sometimes– branchingratios) • Isthere an alternative experimental approachto separate thelow-lyingdipolestrength (or PDR)fromthe GDR ?

  24. Structureofthe PDR: (g,g‘) vs. (a,a‘) vs. (p,p‘) A coincidentdetectionofthegdecayenhancestheselectivity andenergyresolutionof (a,a‘) and (p,p‘) g (a,a‘g) and (p,p‘g) T.D. Poelhekken et al., PLB 278 (1992) 423

  25. (a,a‘g) and (p,p‘g) experiments (a,a‘g) • Ecm = 30-200 MeV/A • BBS@KVI (deceased 15/11/12) • K600 @ iThemba LABS • CAGRA campaign @ RCNP • BigRIPS@RIKEN D. Savran et al., NIM A564(2006) 267 abeam

  26. Structureofthe PDR: (a,a‘g) experiments 124Sn Janis Endres et al., PRL 105 (2010) 112503 Janis Endres et al., PRC 85(2012) 064331

  27. Splitting ofstrength: Experimental results D. Savran et al., PRL 97 (2006) 172502 J. Endres et al., PRC 80 (2009) 034302 J. Endres, E.Litvinovaet al., PRL 105(2010) 212503 V. Derya et al., NPA 906 (2013) 94

  28. Transition densitiesfor 1-states in 208Pb PDR region Equationof Motion Phonon Method GDR region D. Bianco, F. Knapp, N. Lo Iudice, F. Andreozzi, A. Porrino, and P. Vesely, PRC 86 (2012) 044327 gtalkbyF. Knapp

  29. Splitting ofthe PDR: Interpretation from RQTBA Surfaceneutronoscillationmode, the „real“ PDR Isovectormode Janis Endres et al., PRL 105 (2010) 112503 Janis Endres et al., PRC 85 (2012) 064331

  30. gdecay after inelasticscatteringof17O on 208Pb L. Pellegri, A. Bracco, et al., EUNPC 2012 gtalkbyL. Pellegri

  31. Open questions • Systematics (mass, N/Z, exoticity) • Decaypattern • Comparisonofelectromagneticandhadronicexcitation • Single-particlestructure

  32. E1 strength in light nuclei: 40Ca and48Ca V. Derya et al., PLB 730 (2014) 288

  33. Isospinstructureofthe PDR in exoticnuclei: (a,a‘) in inverse kinematicsatBigRIPS@RIKEN liquid 4He NaI+LaBr

  34. Single-particlestructureofthe PDR 119Sn(d,pg)120Sn measured at SONIC@HORUS, Cologne PRELIMINARY, April 2014 S.G. Pickstone, A. Hennig, M. Spieker, V. Derya, M. Weinert, J. Wilhelmy

  35. GDR PDR

  36. GDR PDR

  37. The Pygmy Dipole Resonance – statusandnewdevelopments V. Derya, J. Endres, A. Hennig, J. Mayer, L. Netterdon, S. Pascu, S.G. Pickstone, P. Scholz, M. Spieker, M. Weinert, J. Wilhelmy, and A. Z. Institut für Kernphysik, University of Cologne M.N. Harakeh and H.J. Wörtche KVI Groningen, The Netherlands D. Savran Extreme Matter Institute EMMI, Darmstadt (ZI 510/4-2, SFB 634, INST 216/544-1, and BCGS) supportedby (RII3-CT-2004-506065)

  38. The calculatedneutronskinscaleswiththeCoulomb corrected Fermi energydifferences microscopiccalculations D. Savran, T. Aumann, andA. Zilges, PPNP 70 (2013) 210

  39. Splitting ofthe PDR: Theoryfor124Sn J. Endres, E. Litvinova, V. Ponomarevet al., PRC 85 (2012) 064331

  40. spdf-IBA calculationofthe PDR S. Pascu et al., PRC 85 (2012) 064315

  41. Proton andneutroncontributiontothe PDR E. Yüksel et al., NPA 877 (2012) 35

  42. Isoscalar / isovectorpartofthe E1 strength D. Vretenar et al., arxiv :1202.5663v1

  43. 208Pb: (a,a‘g) vs. (g,g‘) M. Spieker, IKP, University of Cologne

  44. Neutron skinsymmetryenergy L= slopeparameterofsymmetryenergy E1 responsecalculatedwith different RPA modelsbased on Skyrmeeffectiveforces plus mesonexchangeeffectiveLagrangians A. Carbone et al., PRC 81 (2010) 041301(R)

  45. Relevanceof PDR • Universal „collective“ excitationmode • Connection toneutronstarradius, neutronskin P.-G. Reinhard and W. Nazarewicz, PRC 81 (2010) 051303(R) J. Piekarewicz et al., PRC 85 (2012) 041302 (R) J. Erler et al., PRC 87 (2013) 044320

  46. Relevanceof PDR • Universal collectiveexcitationmode • Connection toneutronstarradius, neutronskin • Slopeofsymmetryenergy in EoS A. Carbone et al. PRC 81 (2010) 041301(R)

  47. „PDR“ in title orabstractof PRL, PRC, PLB, NPA • theory/experiment = 2/1 • manymorearticles not usingthedenotation „PDR“ 2000 2005 2010

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