1. Reaction studies with low-energy weakly-bound beams Alessia Di Pietro INFN-Laboratori Nazionali del Sud NN 2015Alessia Di Pietro,INFN-LNS

2. NN 2015Alessia Di Pietro,INFN-LNS Outline 1.Introduction 2.Elastic scattering of weakly-bound and halo nuclei. New results of: I. 6,7 Li+ 64 Zn II. 11 Be+ 197 Au III. 6 He+ 64 Zn 3.Direct reactions 4.Fusion 5.Summary and conclusions

3. NN 2015Alessia Di Pietro,INFN-LNS Exotic structures in light nuclei neutron halo neutron halo proton halo proton halo neutron drip line clusters 10 Be halo nucleus vs normal nucleus

4. NN 2015Alessia Di Pietro,INFN-LNS B(E1) distribution Halo nuclei: e.g. 11 Li, 11 Be, 6 He …. Weakly bound (easy to break-up) Easy to polarise (large B(E1) low energy strenght) Suffer lower Coulomb barrier Higher transfer probability T. Nakamura et al., Phys. Rev. Lett. 96, 252502 (2006). T. Aumann et al., Phys. Rev. C 59, 1252 (1999). N. Fukuda et al., Phys. Rev. C70, 054606 (2004).

5. NN 2015Alessia Di Pietro,INFN-LNS Effects of nuclear structure on collision: the elastic scattering process

6. NN 2015Alessia Di Pietro,INFN-LNS Elastic scattering of weakly bound 6,7 Li on 64 Zn Experiment @ INFN-LNS Above the barrier coupling to continuum effects more important in 6 Li than in 7 Li 6 Li+ 64 Zn 7 Li+ 64 Zn J.P.Fernandez-Garcia et al. submitted to PRC

7. M.Cubero et al., PRL109, 262701 (2012) Elastic scattering of halo nuclei A. Di Pietro et al. PRC 85, 054607 (2012) E lab =24.3 MeV 9,11 Li+ 208 Pb E lab =29.8 MeV Long range absorption effects of both, nuclear and Coulomb origin, accounts for suppression of elastic cross-section.

8. NN 2015 11 Be+ 197 Au @TRIUMF Ge-array TIGRESS: - - detection of E  =0.32 MeV from 11 Be* beam  11 Be Calculations: XCDCC includes a non-spherical 10 Be core. Ι 11 Be(gs)> = a Ι 10 Be(gs)x 2s 1/2 > + b Ι 10 Be(2 + )x 1d 5/2 > + c Ι 10 Be(2 + )x 1d 3/2 > Charged particles: - 3 telescopes DSSSD 16+16 (40µm) + PAD. - 1 telescope SSSD 16 (20 µm) + DSSSD 16+16 (300 µm). Standard CDCC

9. NN 2015Alessia Di Pietro,INFN-LNS New data 6 He+ 64 Zn @ E lab ≈ 15 and 18 MeV SSSD LAMP LEDA beam

10. NN 2015Alessia Di Pietro,INFN-LNS Comparison between 4,6 He+ 64 Zn data at two beam energies 6 He+ 64 Zn E c.m. =12.4 MeV PRC 69,044613(2004) 6 He+ 64 Zn E c.m. =13.7 MeV 4 He+ 64 Zn The elastic angular distributions at two different energies are “almost” the same!

11. NN 2015Alessia Di Pietro,INFN-LNS 6 He+ 64 Zn elastic scattering It seems that the angular distributions at E lab =13.6 MeV and 15 MeV are the same is due to the different contribution of coupling with the trasfer channel ! PRC 69,044613(2004)

12. NN 2015Alessia Di Pietro,INFN-LNS Break-up and transfer processes A.M. Moro et al. PRC 89, 064609 (2014) P C T H Transfer Break-up 6 He+ 64 Zn 11 Be+ 64 Zn 10 Be angular distribution 11 Be+ 64 Zn P C T T+n V. Scuderi et al. PRC 84, 064604 (2011) 6 He+ 64 Zn  65 Zn PRC 84,064604(2011)

13. NN 2015Alessia Di Pietro,INFN-LNS Fusion

14. NN 2015Alessia Di Pietro,INFN-LNS ● There is an effect of the halo structure on fusion ● Static effects appears to be important but not the only ones ● CF appears to be dominant over ICF ● Few data below barrier No clear conclusions can be reached for p-halo nuclei see e.g. : 8 B+ 58 Ni - E.F. Aguilera et al.: PRL 107,092701,(2011) 8 B+ 28 Si - A.Pakou et al.: PRC87,014619,(2013) L.F. Canto et al.: NPA 821,51, (2009) ; P.R.S. Gomes et al.: PRC 79, 027606, (2009) J.Rangel et al.: Eur. Phys. Jour A 49, 57, (2013); Halo nuclei Systematics for fusion with halo nuclei Main ingredient: reduce  Fus (E) to eliminate static effects Further transformation eliminates coupling to bound state effects Fusion of n-halo nuclei

15. NN 2015 L.F. Canto, Nucl. Phys. A 821 (2009) 51 Fusion of weakly bound nuclei with no halo structure Systematic on heavy targets @LNS M.Fisichella et al. to be published

16. NN 2015Alessia Di Pietro,INFN-LNS Break-up dynamics in 6,7 Li+ 144 Sm, 207 Pb and 209 Bi Break-up is triggered predominantly by nucleon transfer. From the relative energy of break- up fragments the time-scale of break-up was deduced and prompt break-up separated by asymptotic break-up.

17. Alessia Di Pietro,INFN-LNS A. Di Pietro et al. PHYS. REV. C 87, 064614 (2013) 6,7 Li+ 64 Zn heavy residue excitation function Ratio of H.R. cross-section NN 2015

18. Heavy Residue relative yields (  H.R. /  tot ) Experiment Complete Fusion calculations d-capture calculations  -capture calculations Is d or  capture from 6 Li important ? ● ICF E *  ( E cm - S  )x(m clu /m proj ) + Q (Clu+64Zn) ● Cluster transfer E *  Q gg – Q opt NN 2015 1n or 1p transfer leading to 65 Zn and 65 Ga can also contribute Above barrier CF dominates Below the barrier different processes dominate A.Di Pietro et al. Phys. Rev. C 87, 064614, (2013)

19. NN 2015Alessia Di Pietro,INFN-LNS Summary and conclusions Reaction studies with halo and weakly bound beams have shown many peculiarities due to the low binding and extended wave function :  Damping of elastic cross-section at large impact parameters due to the coupling to the continuum. Both Coulomb and nuclear coupling contribute to the effect.  Coupling to n-transfer important in 6 He elastic scattering.  Large total reaction cross-sections.  Large cross-section for transfer and breakup events. Different contribution for the different projectiles.  With weakly bound and halo nuclei the suppression of above barrier complete fusion could be due to break-up. Break-up triggered by nucleon transfer has been found to be more important than direct break-up. With lighter masses the observed enhancement below the barrier seem to be due to other processes contributing to the measured cross-section.

20. NN 2015Alessia Di Pietro,INFN-LNS RBI Zagreb