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

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

Ordinary Nucleus Photo- absorption of Nucleus p n Giant Dipole Resonance (GDR) E x ~80A -1/3 MeV ExEx B(E1) (E1 Transition Probability)  (=E  9 Li n n  ExEx (=E  B(E1) (E1 Transition Probability) 10~20MeV 1~2MeV 9 Li Soft E1 Excitation

E1 ? Reaction Mechanism of Soft E1 Excitation? Soft Dipole ResonanceDirect Coulomb Breakup Slow Vibration of core against halo E x (Peak)  8 5 SnSn B(E1)  S n dB(E1) dE x  exp(iqr)| rY 1 m |  gs  | 2 Z A S n (E x - S n ) 3/2 Ex4Ex4  core n c.f. Pigmy Resonance

Coulomb Breakup 11 Be Heavy Target (Pb) 11 Be* 10 Be n  Excitation by a Virtual Photon Cross Section = (Photon Number ） x  Transition Probability)  > 0.3 c Excitation Energy (=Photon Energy ） Invariant Mass Spectroscopy

dB(E1) dE x  exp(iqr)| rY 1 m |  gs  | 2 Z A S n (E x - S n ) 3/2 Ex4Ex4  Huge E1 Probability (usually B(E1) < ) B(E1) Observed for Neutron-halo １１ Be nucleus core n T.Nakamura et al., PLB 331,296(1994) N.Fukuda et al., PRC70, (2004) Direct Breakup Model 11 Be(70MeV/u)+Pb No Resonance But Huge Peak

|  gs (1/2 + )  =  | 10 Be(0 + )  s 1/2  | 10 Be(2 + )  d 5/2      : Spectroscopic factor dB(E1) dE x  exp(iqr)| rY 1 m |  gs  | 2 Z A S n (E x - S n ) 3/2 Ex4Ex4   -S n  ~   |exp(-r/ )/r| 2 Fourier Transform Low-energy B(E1) Halo State 11 Be ground state Halo State Non-Halo State Low-energy B(E1)---Very Sensitive to Halo Wave Function !   = 0.72  N.Fukuda, TN et al., PRC70, (2004)   = 0.61  R.Palit et al., PRC68, (2003).

Coulomb Breakup of 15 C 2 Application to Astrophysics

Burning zone in Low mass Asymptotic Giant Branch(AGB) stars Neutrons from 13 C(  n ) reaction 14 C(n,  ) 15 C(   ) 15 N(n,  ) 16 N(   ) 16 O(n,  ) 17 O(n,  ) 14 C M.Wiescher et al., ApJ, 363, C(n,  ) 15 C 15 C( ,n) 14 C Neutron Capture Reaction  Coulomb Dissociation Inhomogeneous Big Bang Model r-process model Terasawa,Sumiyoshi,Kajino, ApJ562,470(2001). 14 C(n,  ) 15 C: Beer et al.(Karlsruhe), 1/5 of Direct Capture, APJ387,258 (1992) R.Reifarth et al.(Karlsruhe), Consitent with Direct Capture PRC77,015804(2008) 15 C( ,n) 14 C: 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) Previous Experiments

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

15  2 =0.75(4) Results: Coulomb Breakup of 15 C  14 C(0 + )  2s 1/2   14 C(2 + )  1d 5/2  15 C(g.s)= Consistent with GSI (   =0.73) (D.Pramanik et al) Data But not with MSU data r 0 =1.25 fm a=0.65 fm 15 C: moderate neutron-halo 1/2 + gs, S n =1.27MeV

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

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

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

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

One neutron halo nucleus vs. Two neutron halo nucleus 9Li9Li n n 10 Be n Motion between core and 1 valence neutron Motion between 1.Core and neutron 2.Core and neutron 3.Two valence neutrons (neutron-neutron correlations) S 2n =300 keV S n =504 keV

Coulomb Breakup of 11 Li (Summary of Previous Results) 43MeV/nucleon PLB348 (1995) 29. NPA 619 (1997) MeV/nucleon PRL 70 (1993) 730. PRC 48(1993) 118.

11 Li 9 Li n n Experimental at RIKEN Pb Target NEUT HOD BOMAG DC DALI 70MeV/nucleon

Examine Different Wall Events t1t1 t2t2 11 22  12 Condition: Almost no bias E th =6MeVee to avoid any gamma related events Elimination of Cross-Talk events

Coulomb Dissociation Spectrum of 11 Li Angular Distribution

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

Non-energy weighted E1 Cluster Sum Rule r1r1 r2r2 n 9 Li r c-2n (Extrapolated value) ~70% larger than non-correlated strength

Implication of the Narrow Opening Angle r1r1 r2r2 n 9 Li r c-2n Simple two-neutron shell model Melting of s(+ parity) and p(-parity) orbitals Mixture of different parity states is essential ! If full overlap (1s) 2 & (0p) 2 If only (1s) 2 or (0p) 2 If 50% overlap integral Mixture of higher L orbitals  More correlated H.Simon et al. PRL83,496(1999). N. Aoi et al. NPA616,181c(1997).

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

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

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

4 SAMURAI Project at RI Beam Factory

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

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

Summary Strong B(E1) at very low excitation energy neutron-neutron spatial correlation from E1 sum rule  nn ~50deg Soft E1 Excitation of 2n halo nucleus -- Coulomb Breakup of 11 Li 1 T. Nakamura, A.M.Vinodkumar et al., Phys. Rev. Lett. 96, (2006). 2 Coulomb Breakup of 15 C: Application to Astrophysics 3 Soft E1 Excitation of 1n halo nucleus--- Coulomb Breakup of 11 Be T.N et al.,PLB 331,296(1994); N.Fukuda, TN et al.,PRC70, (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) 14 C(n.  ) 15 C can be studied by Coulomb breakup of 15 C P-wave direct capture  Direct breakup of Halo (s-wave) 4 SAMURAI Project (~4W.u)

R301n Collaboration: (Coulomb Breakup of 11 Li) T.Nakamura 1, A.M. Vinodkumar 1,T.Sugimoto 1,N.Aoi 2, H.Baba 2, D.Bazin 4, N.Fukuda 2, T.Gomi 2, H.Hasegawa 3, N. Imai 5, M.Ishihara 2, T.Kobayashi 6, Y.Kondo 1, T.Kubo 2, M.Miura 1, T.Motobayashi 2, H.Otsu 6, A.Saito 7, H.Sakurai 2, S.Shimoura 7, K.Watanabe 6, Y.X.Watanabe 5, T.Yakushiji 6, Y. Yanagisawa 2, Y.Yoneda 2 1. Tokyo Inst. of Technology 2. RIKEN 3. Rikkyo Univ 4. NSCL, MSU 5. KEK, 6. Tohoku University 7. CNS, Univ. of Tokyo

Peak at E rel =S n

MACS(Maxwellian-averaged neutron capture cross section) = 7.4(4)  b