1. Study of breakup mechanism of a loosely bound projectile in a region of Coulomb breakup dominance H. Okamura, K. Hatanaka, A. Tamii (RCNP) K. Sekiguchi, K. Suda (Nishina Center, RIKEN) H. Sakai, K. Yako, T. Uesaka, T. Saitoh (Univ. Tokyo) T. Wakasa (Kyushu Univ.) Y. Maeda (Miyazaki Univ.) K. Itoh, T. Ikeda, H. Kumasaka, R. Suzuki (Saitama Univ.) The 19th International Conference on Few-Body Problems in Physics (FB19) Bonn, Germany, August 31 – September 5, 2009 Outline: Introduction Coulomb-breakup & deuteron previous study at  p =  n = 0  & E d = 56, 140, 270 MeV  its defects Experiment Result for 12 C, 40 Ca, 90 Zr, 208 Pb at  p = 0  7 ,  n = 0  8  Analysis  finite-range post-DWBA Summary & prospect deuteron

2. Coulomb breakup convenient way to imitate radiative capture at extremely low- E ? p C D  ~keV radiative capture Coulomb breakup relevant to stellar-synthesis difficult direct-measurement small-c.s. at low- E C can be unstable large cross section due to high-flux  at high- E proj.-fragmentation allows use of unstable beams However, virtual-  also contributes to distortion (post-acceleration) nuclear interaction also contributes to breakup reliable treatment of reaction mechanism must be established. p C D virtual-  A small rel- E ~100 MeV/A

3. one of the most loosely bound (stable) nuclei well understood wave func. w/o resonance (direct breakup) distinctively different nuclear & Coulomb breakup spectra in 1st order while large post-acceleration effect  large Z / m diff. large nuclear breakup contrib.  small Z p These features will be useful for detailed study of breakup mechanism. Deuteron proton- energy spectra However, in spite of long history of deuteron breakup, data with Coulomb-breakup dominance are rare. EpEp

4. H. Okamura et al., Phys. Lett. B325 (1994) 308 Phys. Rev. C 58 (1998) 2180 Previous data First obs. of Coulomb b.u. dominance of deuteron at  p ~  n = 0  & 56, 140, 270 MeV for targets from 12 C thru 208 Pb pure-Coulomb cals. (solid line) fairly well explain data, but...

5. pure-Coulomb cal. predicts complicated distributions, which, however, were not observed in previous data.  n =0  EpEp pp 40 Ca 118 Sn 208 Pb 40 Ca 208 Pb pp nn  10   10 

6. Previous Setup @RIKEN SMART Q-Q-D focus-type spectrograph resulted in poor (vertical) angular resolution for proton (avr.  2.2  ) limited angular acceptance for neutron

7. Present Setup @RCNP ESS-course E d = 140 MeV Simple C-shaped dipole-mag. allows 40 < E p < 100 MeV 0  <  p < +10   10  <  n < +10  in coplanar geom. utilizing bend. mag. of old WN course

8. Results E d = 140 MeV, bin width 1  (0.5  @  = 0  )

9. Results small q large  np large q small  np Double-peak at  p =  n = 0  w/ sharp dip at E p =E n (  np = 0) Rapid change of shape depending on  Opposite side (smaller q, larger  np ) favored Ep=EnEp=En E d = 140 MeV, bin width 1  (0.5  @  = 0  )

10. Results Almost the same distributions with those of 12 C Larger cross section, approximately scaled by Z 2 small q large  np large q small  np E d = 140 MeV, bin width 1  (0.5  @  = 0  )

11. Results Distributions change (only) slightly from 40 Ca & 12 C small q large  np large q small  np E d = 140 MeV, bin width 1  (0.5  @  = 0  )

12. Results Drastic change of distributions; strong suppression @ 0  &  n =  p (opposite side) enhancement in neighboring (backward) angles small q large  np large q small  np E d = 140 MeV, bin width 1  (0.5  @  = 0  )

13. An analysis  finite-range post-form DWBA prior-form : large V l contrib.  CDCC post-form : small remnant term  DWBA ? advantage in treatment of unbalanced Coulomb int. pure-Coulomb case also from adiabatic approx.(+LMA?), J.A.Tostevin et al. PRC 57 (’98) 3225 local mom. approx. n p A r R n p A r R troublesome continuum coupling Nuclear interaction makes the problem a bit involved. N.B. Baur & Trautmann (  30 yrs ago) used Zero-Range Approx., while k d = 3.8 fm  1 @ 140 MeV

14. Finite-Range calc. utilizing Coulomb-wave expansion & pure-Coulomb T -matrix like plane-wave expd in DWUCK5 for trans. reaction, e.g. ( d, p ) q -integ. for each partial-wave l & angular integ. with Lebedev-Laikov grid LMA k

15. Exact DWBA LMA Exact DWBA LMA Validity of LMA was previously examined by comparison with Exact DWBA for pure-Coulomb breakup reasonable agreement for ( d, p n ) discrepancy becomes larger for ( 11 Be, 10 Be n ) M. Zadro PRC 66 (2002) 034603

16. Optical potentials for describing distorted-waves H. Okamura et al., Phys. Rev. C 58 (1998) 2180 deuteron Elastic-scatt. at 140 MeV were previously measure at RIKEN Consistent with recent global-potential H. An & C. Cai, Phys. Rev. C 73 (2006) 054605 proton & neutron Several global-potential are available in this region A.J. Koning & J.P. Delaroche, Nucl. Phys. A 713 (2003) 231 N.B. energy-dependence is taken into account for ejectiles p & n using global potentials

17. Too asymmetric N over-contrib.? Results of F.R. post-DWBA pure-Coulomb & Coul.+Nucl. Pure-Coulomb cal. account for data at 0  & small q. Nuclear int. improves at (some) backward angles (for n ), but makes double-peak much too asymmetric (over-contrib.) N-dominant C-dominant

18. Results of F.R. post-DWBA pure-Coulomb & Coul.+Nucl. Pure-Coulomb cal. account for data at 0  & small q. Nuclear int. improves at (some) backward angles (for n ), but makes double-peak much too asymmetric (over-contrib.)

19. Results of F.R. post-DWBA pure-Coulomb & Coul.+Nucl. Pure-Coulomb cal. account for data at 0  & small q. Nuclear int. improves at (some) backward angles (for n ), but makes double-peak much too asymmetric (over-contrib.)

20. Results of F.R. post-DWBA pure-Coulomb & Coul.+Nucl. Pure-Coulomb cal. roughly account for data in whole region. Nuclear int. contributes differently from lighter targets. Need more efforts to understand whole spectra.

21. Summary & Prospect (d,pn) elastic breakup has been measured at E d = 140 MeV, 40  E p  100 MeV, 0   p  +10 ,  10   n  +10 , with a resolution  0.5 , for 12 C, 40 Ca, 90 Zr, 208 Pb. Observed double-peak at 0  (  Coulomb b.u. dominance) and complicated ang.-dist., which are NOT scaled by Z 2, even drastic change between 208 Pb and lighter targets.  critical test ground for breakup reaction theory Finite-range post-form DWBA cal. has been made. Pure-Coulomb cal. roughly accounts for  p =  n ( q ~0) data. Nuclear int. improves larger  data, but overestimates contrib. presumably due to p - n FSI ( V np treated perturbatively). Better treatment is necessary also for heavier system breakup destructive, because of orthogonality between bound & unbound states Thank you for your attention

22. n -eff. & p -traj. were calibrated using 70-MeV p (H 2 + ) beam

23. Bird View of RCNP Cyclotron Facility ESS course AVF Ring G-Raiden N0

24. UCN (old)