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E1 Strength distribution of halo nuclei observed via the Coulomb breakup

E1 Strength distribution of halo nuclei observed via the Coulomb breakup. Takashi Nakamura Tokyo Institute of Technology. Workshop on Statistical Nuclear Physics and Applications in Astrophysics and Technology, OHIO University, July 2008. Contents. 1. Introduction.

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E1 Strength distribution of halo nuclei observed via the Coulomb breakup

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  1. E1 Strength distribution of halo nuclei observed via the Coulomb breakup Takashi Nakamura Tokyo Institute of Technology Workshop on Statistical Nuclear Physics and Applications in Astrophysics and Technology, OHIO University, July 2008

  2. Contents 1 Introduction Soft E1 Excitation of 1n halo nucleus--- Coulomb Breakup of 11Be T.Nakamura et al.,PLB 331,296(1994). N.Fukuda, TN et al.,PRC70, 054606 (2004). Coulomb Breakup of 15C: Application to Astrophysics 2 Paper in preparation Soft E1 Excitation of 2n halo nucleus --Coulomb Breakup of 11Li 3 T. Nakamura, A.M.Vinodkumar et al.,PRL96, 252502 (2006). 4 SAMURAI Project @ RIBF

  3. g Photo- absorption of Nucleus B(E1) (E1 Transition Probability) Ordinary Nucleus Ex~80A-1/3MeV p Giant Dipole Resonance (GDR) n g Ex 10~20MeV (=Eg) B(E1) (E1 Transition Probability) n 9Li 9Li n Soft E1 Excitation 1~2MeV Ex 10~20MeV (=Eg)

  4. dB(E1) Z µ| á exp(iqr)| rY1m|Fgsñ |2 dEx A Sn (Ex - Sn)3/2 µ Ex4 Reaction Mechanism of Soft E1 Excitation? ? E1 Soft Dipole Resonance Direct Coulomb Breakup core n Slow Vibration of core against halo 8 c.f. Pigmy Resonance Ex(Peak) µ Sn B(E1) µ 1/ Sn 5

  5. Coulomb Breakup 10Be 11Be* 11Be n g b > 0.3c Heavy Target (Pb) Excitation by a Virtual Photon Excitation Energy (=Photon Energy） Cross Section = (Photon Number）x(Transition Probability) Invariant Mass Spectroscopy

  6. B(E1) Observed for Neutron-halo１１Be nucleus 11Be(70MeV/u)+Pb Huge E1 Probability (usually B(E1) < 10-3) T.Nakamura et al., PLB 331,296(1994) N.Fukuda et al., PRC70, 054606 (2004) No Resonance But Huge Peak Direct Breakup Model dB(E1) Z µ| á exp(iqr)| rY1m|Fgsñ |2 core dEx A n Sn (Ex - Sn)3/2 µ Ex4

  7. Low-energy B(E1)---Very Sensitive to Halo Wave Function ! r ~ a2 |exp(-r/l)/r|2 dB(E1) Z µ| á exp(iqr)| rY1m|Fgsñ |2 dEx A Sn (Ex - Sn)3/2 -Sn µ a2 Halo State Ex4 Low-energy B(E1) Fourier Transform 11Be ground state Non-Halo State Halo State | Fgs (1/2+)ñ = a |10Be(0+)Ä2s1/2 ñ + b|10Be(2+)Ä1d5/2 ñ a2,b2: Spectroscopic factor a2 = 0.72±0.04 N.Fukuda, TN et al., PRC70, 054606 (2004) a2 = 0.61±0.05 R.Palit et al., PRC68, 034318 (2003).

  8. Coulomb Breakup of 15C 2 Application to Astrophysics

  9. Neutron Capture Reaction  Coulomb Dissociation 15C(g,n)14C 14C(n,g)15C Burning zone in Low mass Asymptotic Giant Branch(AGB) stars Neutrons from 13C(a,n) reaction 14C(n,g)15C(b-)15N(n,g)16N(b-)16O(n,g)17O(n,a)14C M.Wiescher et al., ApJ, 363,340 Inhomogeneous Big Bang Model r-process model Terasawa,Sumiyoshi,Kajino, ApJ562,470(2001). Previous Experiments 14C(n,g)15C: Beer et al.(Karlsruhe), 1/5 of Direct Capture, APJ387,258 (1992) R.Reifarth et al.(Karlsruhe), Consitent with Direct Capture PRC77,015804(2008) 15C(g,n)14C: Coulomb breakup Horvath et al.(MSU), Inconsistent with Direct breakup APJ570, 926(2001) D. Pramanik et al.(GSI), Consistent with Direct breakup PLB551,63(2003)

  10. Neutron Capture Reaction vs. Coulomb Dissociation 14C(n,g)15C 15C(g,n)14C Neutron CaptureCoulomb Dissociation The principle of detailed balance Advantages of Coulomb Dissociation Phase Factor ~100, Photon Number ~500 Target(Thick, Stable), Kinematical Focusing

  11. Results: Coulomb Breakup of 15C 15C: moderate neutron-halo 1/2+ gs, Sn=1.27MeV +bê14C(2+)Ä1d5/2 ñ aê14C(0+)Ä2s1/2 ñ 15C(g.s)= 15C+Pb@68MeV/u a2=0.75(4) r0=1.25 fm a=0.65 fm Consistent with GSI (a2=0.73) (D.Pramanik et al) Data But not with MSU data

  12. Neutron Capture Cross Section From the data with b>20fm Consistent with Direct Capture Measurement 14C(n,g)15C By R.Reifarth et al., PRC77,015804(2008)

  13. s-wave capture vs. p-wave capture A(n,g)B(Normal) S-wave capture dominant A(n,g)B(Halo) p-wave capture dominant p-wave s-wave En

  14. Experimental Input Coulomb Breakup of 19C T.Nakamura et al.,PRL83,1112(1999). 18C(n,g)19C Case Conventional Calculation(HF) Theoretical Results: T.Sasaqui, T.Kajino, G.J.Mathews, K.Otsuki, T.Nakamura, Astrophys.J. 634, 1173 (2005).

  15. Coulomb Breakup of halo nuclei 11Li 3 T. Nakamura, A.M.Vinodkumar et al., Phys. Rev. Lett. 96, 252502 (2006).

  16. One neutron halo nucleus vs. Two neutron halo nucleus n n 9Li 10Be S2n=300 keV Sn=504 keV n Motion between core and 1 valence neutron • Motion between • Core and neutron • Core and neutron • Two valence neutrons • (neutron-neutron correlations)

  17. Coulomb Breakup of 11Li (Summary of Previous Results) MSU@ 28MeV/nucleon PRL 70 (1993) 730. PRC 48(1993) 118. RIKEN @ 43MeV/nucleon PLB348 (1995) 29. GSI @280MeV/nucleon NPA 619 (1997) 151.

  18. Experimental Setup NEUT @RIPS at RIKEN n n Pb Target 9Li HOD DC DALI 11Li 70MeV/nucleon BOMAG

  19. Elimination of Cross-Talk events Examine Different Wall Events Almost no bias Condition: t1 b1 b12 b2 t2 Eth=6MeVee to avoid any gamma related events

  20. Coulomb Dissociation Spectrum of 11Li Angular Distribution

  21. Comparison with a 3-body theory Calculation H.Esbensen and G.F. Bertsch NPA542(1992)310. “Soft dipole excitations in 11Li” Comparison with Previous results

  22. Non-energy weightedE1 Cluster Sum Rule rc-2n r2 n r1 9Li (Extrapolated value) ~70% larger than non-correlated strength

  23. If only (1s)2 or (0p)2 If full overlap (1s)2 & (0p)2 If 50% overlap integral Implication of the Narrow Opening Angle Simple two-neutron shell model rc-2n r2 n r1 Melting of s(+ parity) and p(-parity) orbitals 9Li H.Simon et al. PRL83,496(1999). N. Aoi et al. NPA616,181c(1997). Mixture of different parity states is essential ! Mixture of higher L orbitals More correlated

  24. Simulation (Phase Space) E(9Li-n) E(9Li-n) E(9Li-n) Further Correlation? n E(9Li-n) 9Li Experimental Result 1MeV E(9Li-n) E(9Li-n) 1MeV preliminary

  25. p-wave? 10Li s-wave Virtual state Obataind from 11Li+C9Li+n spectrum

  26. 1MeV E(n-n) n n E(9Li-nn) 9Li E(n-n) 1MeV E(9Li-nn) preliminary

  27. SAMURAI Projectat RI Beam Factory 4

  28. RIBF (RIKEN RI Beam Factory) For the future Samurai K=2400MeV E/A=350MeV 8Tm 6%, 100mrad Facility before 2007 Completed in 2007 World Largest RI-beam facility New Facility 100MeV/nucleon 350MeV/nucleon, ~1pmA Heavy ions up to U beam

  29. SAMURAI Superconducting Analyser for MUlti-particles from RAdio-Isotope Beam Funded! 2008-2011 1.5GJPY~15MUSD~10MEuro Superconducting Magnet To let neutron(s) pass through the gap Sweep Beam and Charged Fragments Good Mass Resolution for PID @ A~100 +NEBULA (NEutron Detection System for Breakup of Unstable Nuclei with Large Acceptance) Bending Power BL=7Tm (B=3Tesla, 60deg bending)

  30. Summary 1 Soft E1 Excitation of 1n halo nucleus---Coulomb Breakup of 11BeT.N et al.,PLB 331,296(1994); N.Fukuda, TN et al.,PRC70, 054606 (2004). • Large E1 strength ~3W.u. at low excitation energies • Direct Breakup Mechanism– Reflecting Large amplitude of Halo state • Coulomb Breakup---Spectroscopic Tool (spectroscopic factors) 2 Coulomb Breakup of 15C: Application to Astrophysics • 14C(n.g)15C can be studied by Coulomb breakup of 15C • P-wave direct captureDirect breakup of Halo (s-wave) Soft E1 Excitation of 2n halo nucleus --Coulomb Breakup of 11Li 3 T. Nakamura, A.M.Vinodkumar et al., Phys. Rev. Lett. 96, 252502 (2006). (~4W.u) • Strong B(E1) at very low excitation energy • neutron-neutron spatial correlation from E1 sum rule qnn~50deg SAMURAI Project 4

  31. R301n Collaboration: (Coulomb Breakup of 11Li) T.Nakamura1, A.M. Vinodkumar1,T.Sugimoto1,N.Aoi2, H.Baba2, D.Bazin4, N.Fukuda2, T.Gomi2, H.Hasegawa3, N. Imai5, M.Ishihara2, T.Kobayashi6, Y.Kondo1, T.Kubo2, M.Miura1, T.Motobayashi2, H.Otsu6, A.Saito7, H.Sakurai2, S.Shimoura7, K.Watanabe6, Y.X.Watanabe5, T.Yakushiji6, Y. Yanagisawa2, Y.Yoneda2 1. Tokyo Inst. of Technology 2. RIKEN 3. Rikkyo Univ 4. NSCL, MSU 5. KEK, 6. Tohoku University 7. CNS, Univ. of Tokyo

  32. Peak at Erel=Sn

  33. MACS(Maxwellian-averaged neutron capture cross section) = 7.4(4) mb

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