DREB2014 - Direct Reactions with Exotic Beams

The structure of halo nuclei is a subject of intense research in nuclear physics. Of particular interest in three body systems is the existence of Efimov states [1]. This special class of Borromean states appear when the scattering length associated with the underlying two-body force is much larger than its range. Interestingly, Efimov, in his original publication, used nuclear states as possible examples. To date, however, no evidence for such states have been found in nuclei and only recently in ultracold Cs atoms [2]. In recent works [3,4], 20C has been suggested as a potential candidate for which an excited Efimov state exists. Other cases may include 19B [5] and 60Ca [6]. In ref. [4], Canham and Hammer study the universal properties of halo nuclei on the basis of an effective field theory. This approach provides an excellent tool, given the separation of energy scales, to treat the nucleus as an effective three body system of the form neutron-neutron-Core. The properties of these states scale as a function of the dimensionless universal parameter ( lambda0) which in the limit of large core masses approaches ~16. In this work, we ask ourselves how can we study these intriguing states in exotic nuclei ? Mazumdar et al. [3] have suggested the study of Fano resonances in neutron scattering but this is not possible at this time. Here, we envision a few alternatives that should be explored. In particular, if nucleus Z[A]N is a potential candidate, we consider: 1) One neutron transfer: Z[A-1] N-1 (d,p) A, as a surrogate of the neutron scattering, 2) Two-neutron transfer: Z[A-2]N-2 (t,p) A , and 3) Inelastic scattering: A (x,x'). We will present simple arguments to estimate the cross sections for these reactions in terms of the scaling parameter and discuss possible implications. We hope that these initial estimates will serve as a starting point for more refined and realistic calculations which will be required for careful experimental planning and further analysis. [1] V. Efimov , Phys. Lett. B 33 (1970) 563 [2] T.Kraemer et al. , Nature 440 (2006) 315 [3] I. Mazumdar, A.R.P.Rau, V.S.Bhasin, PRL 97 (2006) 062503 [4] D. Canham and H-W. Hammer, EPJA 37 (2008) 367 [5] A. Spyrou et al. PLB 683 (2010) 129 [6] G.Hagen et al. PRL 111 (2013) 132501

The region around neutron-rich N=40 nuclei has recently attracted a lot of interest. The high-lying 2+ state in 68Ni and its small transition probability to the ground state are a result of the N=40 harmonic oscillator shell gap between the fp shell and the 1g9/2 orbital. This shell gap is reduced for the more neutron-rich Fe and Cr isotopes; both the N=40 isotones 66Fe and 64Cr show an increase in quadrupole collectivity. This behavior is caused by quadrupole correlations which favor energetically the deformed intruder states from the neutron g9/2 and d5/2 orbitals. In the shell model the increase in B(E2) values and the decrease in 2+ excitation energy can be reproduced if the neutron g9/2 and d5/2 intruder orbitals are included in the model space. Spectroscopic studies of neutron-rich nuclei around N=40 have been performed at the NSCL utilizing the S800 spectrometer and the GRETINA gamma detector array. The study focused on the one-neutron removal reactions from 68Ni and 64,66Fe. The longitudinal momentum distribution of reaction residues indicates the angular momentum of the removed nucleon, and spectroscopic factors can be extracted from the measured cross section for the population of individual states in the odd-mass residual nucleus. An experimental challenge in this region of the nuclear chart is the occurrence of low-lying isomeric states resulting from the neutron g9/2 intruder orbital. This experiment employs a new technique of combined prompt and delayed gamma-spectroscopy allowing to quantify the occupancy of the intruder neutron g9/2 and d5/2 orbitals in 68Ni and 64,66Fe. Comparison of the measured spectroscopic factors with large-scale shell model calculations show a significant occupation of the intruder orbitals across the N=40 sub-shell gap. Therefore the existence of a new "Island of Inversion'' at N=40 has been experimentally verified for the first time.

In order to study weakly-bound systems, such as halo nuclei, it is essential to take into account the unbound states of the system. Since these unbound states form a continuum of energies, their inclusion in reaction calculations requires the introduction of a discretization method, i.e., the representation of the continuum by a finite and discrete basis. The binning procedure is the discretization method that has been traditionally used within the standard Continuum-Discretized Coupled-Channels (CDCC) formalism for 2-body projectiles (3-body CDCC). In 2009, it was extended to 3-body projectiles (4-body CDCC) [PRC 80 051601(R)], in order to be applied to Borromean halo nuclei such as 6He (4He+n+n) and 11Li (9Li+n+n). The binning procedure has shown to be more appropriate than other discretization methods in order to describe the reactions induced by Borromean nuclei at energies around to the Coulomb barrier. The recent experimental data on 11Li+208Pb at incident energies 24.3 and 29.8 MeV, measured at TRIUMF, are analyzed within the 4-body CDCC formalism including the binning procedure. The comparison between data and 4b-CDCC suggests the presence of a low-lying dipole resonance in 11Li close to the breakup threshold. These results have been recently published in Phys. Rev. Lett. [PRL 109 262701; PRL 110 142701].

Studying nuclear systems at the limit of stability and beyond has had a large impact on the understanding of the ingredients to the nuclear force, in particular since the availability of more and more exotic radioactive beams has increased in recent years at international rare-beam facilities. While at the neutron-rich side of the nuclear chart the binding potentials are shallow - leading to well-established halo phenomena in combination with difficulties to determine the location of the n-dripline - on the proton-rich side the situation is quite reversed: The p-dripline is known, up to Z=91, while halo-states find it hard to evolve due to the additional Coulomb barrier. Around here is were the presented study is located: an experimental investigation of the structure of the Borromean p-dripline nucleus 17Ne, and the connection to its neighbours beyond the dripline. Within the R3B collaboration, we have studied nuclear breakup of high-energy (500 MeV/u) 17Ne beams utilising the R3B-LAND complete kinematics reaction setup at GSI. One-proton knockout on 17Ne, crossing the p-dripline along Z, allowed us for studying in detail the unbound 16F system and extracting, for example, the s/d configuration mixture in the 17Ne ground-state, which is the key quantity determining its discussed 2p halo structure. An analysis of the 15O-p relative energy spectrum, the 16F momentum distributions and profile, combined with the obtained total and partial cross sections and spectroscopic strength give a consistent picture. Beyond that, we were able to observe and study 1n and 2n knockout reactions on 17Ne, crossing the proton-dripline along N, and populating the unbound nucleus 16Ne and, as the very first observation of this nucleus, also 15Ne. We have measured the 16Ne and 15Ne three-body energy spectra in terms of 14,13O+2p, extracted position and width of their ground and first two excited states, and used the f-p-p three-body correlations to deduce properties of their decay mechanism. A comparison to the 17Ne three-body continuum spectrum will be attempted, together with an outlook on further interesting decay channels accessible within our data.

Structures of the neutron-rich nuclei around $N=20$ nucleus ${}^{32}$Mg have been studied via the direct reactions induced by the isoscalar probe of $\alpha$ particle. An array of position sensitive segmented Ge detectors, GRAPE, was employed for the in-beam $\gamma$-ray spectroscopy. Special attention is paid to single-particle states populated via the nucleon transfer reactions as well as collective states appeared in the inelastic scattering to clarify the shell evolution in the island-of-inversion nuclei. The ${}^{32}$Mg is known to have large $B(E2:0_{g.s}^{+}\to 2_1^{+})$ from the Coulomb excitation and also the proton inelastic scattering. In the present study, we discuss the differential cross sections of ${}^{32}$Mg and its neighboring nucleus ${}^{33}$Al with $\alpha$ particles. We also discuss the systematics of the deformation in this region using the same probe for the cocktail beam of Na, Mg, and Al. The experiment was performed at RIPS in RIBF, RIKEN. A 63-$A$MeV ${}^{40}$Ar beam from the ring cyclotron bombarded the 1-mm thick carbon target. Its fragmentation produces was separated by RIPS. The secondary beam bombarded the 150-mm/cm${}^{2}thickliquidheliumtarget.Incidentandoutgoingparticleswereidentifiedinevent-by-eventbasis.Fortheidentificationofoutgoingparticles,aTOF-spectrometerconsistingofasuperconductingtripletquadruplemagnet,alayerofstrippedsilicondetectorandNaIcalorimeter.Theexcitedstateswereidentifiedbythede-excitation$\gamma$raysmeasuredwiththeGRAPE.$\gamma-\gamma$ coincidence analysis was performed to reconstruct the level structure. For the low-lying levels, the angular distributions of differential cross sections were obtained. The deformation parameter was deduced by DWBA analysis. In this paper, we will report the excitation structures in island-of-inversion nuclei using the isoscalar probe and discuss their structures from the point of view of deformation.

The region around the nucleus 68Ni, with a shell closure at Z = 28 and a sub-shell closure at N = 40, is the source of considerable interest in nuclear-structure studies. Despite a significant set of experimental and theoretical information available on 68Ni [1, 2, 3, 4, 5], the origin of its structure is still being questioned. A recent clarification of the energy and spin assignment of several low-lying 0+ and 2+ states [6, 7, 8, 9] and state-of-the-art shell model calculations [10] hinted to the possibility of triple shape coexistence and highlighted the need of additional experimental investigation. To better understand the structure of 68Ni, we performed a two-neutron transfer experiment on 66Ni at 2.85 MeV/u at ISOLDE, CERN. This 66Ni(t,p)68Ni reaction with a radioactive beam and target represents a unique tool to probe the nature of 0+ states in 68Ni. Coincidences between the outgoing light charged particles and γ-rays were detected using the combined MINIBALL [11] gamma-ray spectrometer and the T-REX particle detection array [12]. Results of such coincidence analysis together with the reconstruction of angular distributions of the reaction products, revealing the most populated states, will be presented. An interpretation based on calculations within the Distorted-Wave Born Approximation (DWBA) and shell model two-nucleon amplitudes will be discussed. 1] M. Bernas et al., PLB 113, 279 (1982). [2] R. Broda et al., PRL 74, 868 (1995). [3] W. Mueller et al., PRC 61, 054308 (2000). [4] O. Sorlin et al., PRL 88, 092501 (2002). [5] S. Lenzi et al., PRC 82, 054301 (2010). [6] F. Recchia et al., PRC 88, 041302 (2013). [7] S. Suchyta et al., PRC 89, 021301R (2014). [8] C. J. Chiara et al., PRC 86, 041304 (2012). [9] R. Broda et al., PRC 86, 064312 (2012). [10] D. Tsunoda et al., PRC 89 031301R (2014). [11] N. Warr et al., EPJA 49, 40 (2013). [12] V. Bildstein et al., EPJA 48, 85 (2012).

The Sn isotopes between N=50 and N=82 are the longest chain of semi-magic nuclei accessible to nuclear structure studies. They provide an ideal testing ground to study the evolution of shell structure with isospin. Among them 100Sn, the heaviest proton-bound self-conjugate nucleus, is a unique case for studying single-particle energies and residual interactions far from the line of stability. In addition, neutron-proton correlations are expected to play a significant role in 100Sn. The collectivity is expected to have a parabolic evolution with the maximum at the middle of the d5/2g7/2s1/2d3/2h11/2 shell. Recent Coulomb excitation experiments do not display such a drop of collectivity approaching the proton drip line. Limitations in the valence space, and namely the neglect of excitations across the N=50 gap, are pointed out as possible reasons for this failure. We performed an experiment at the RIKEN RIBF facility to tackle these questions using complementary experimental probes: Coulomb excitation, inelastic scattering, two-neutrons knockout. The DALI2 gamma spectrometer was used to study the spectroscopy of 102,104Sn produced after reaction on a Pb, C and CH2 target, while the heavy residues where identified in the ZeroDegree Spectrometer. A reference measurement with 112Sn was also performed. The results of the Coulomb excitation measurement confirm the persistence of collectivity approaching 100Sn [1]. Inelastic scattering data shed new light on the role of neutron excitations in the collectivity of light Sn isotopes [2], that has been interpreted with help of new QRPA calculations with the Gogny D1S force [3]. Inclusive cross sections for C and H induced knockout come out to be very similar (2.1 and 2.6 mb, respectively) [3], while a stronger population of excited states is observed with an H probe [2]. New transitions have been observed in 102,104Sn. Based on these results, the spectroscopy of 100Sn via H-induced two-neutrons knockout appears to be feasible at RIBF in the near future. [1] P. Doornenbal, S. Takeuchi et al., arxiv.org/abs/1305.2877 (2013) [2] A. Corsi, S. Boissinot, A. Obertelli, P. Doornenbal et al., in preparation (2014) [3] M.Martini, S. Peru, M.Dupuis, Phys.Rev. C 83, 034309 (2011) [4] L. Audirac, A. Obertelli et al., Phys. Rev. C 88, 041602 (2013)

The study of the unbound system 10Li is of great interest since the knowledge of its structure is a crucial ingredient in the description of the two-neutron halo nucleus 11Li. Despite the significant amount of experimental information gathered during the last years, the properties of the 10Li continuum remains unclear, to the extent that even the energy and the spin-parity of the ground state are still controversial. It is widely accepted that it is formed by either a 1p1/2 or 2s1/2 neutron which, coupled to the 3/2- spin of the 9Li core, would produce 1+, 2+ or 1-, 2- states, respectively. However, some calculations suggest that the ground state would correspond to an s-wave [1,2], whereas others conclude that it should be due to a p-wave coupling [3]. Indications of the presence of a low-lying virtual intruder s-state have been also reported [4] and are consistent with the trend of the N = 7 isotones, that should result in a parity inversion in the 10Li case. Nevertheless, due to the limitations of the existing data [5], many of the details predicted by the theory have not been tested. We have investigated the 10Li structure via the 9Li(d,p)10Li transfer reaction in inverse kinematics at TRIUMF. A 100 MeV 9Li beam, produced by the ISAC-II facility, impinged on a CD2 target. The recoiling protons were detected at backward angles by the LEDA array of silicon strip detectors [6], thus allowing the study of the 10Li emitted in the crucial region at forward angles. Protons are detected in coincidence with the 9Li fragments produced from the breakup of the corresponding 10Li. 9Li fragments have been detected and identified by using a ΔE-E telescope of S2 annular DSSD detectors located downstream the target. The 10Li excitation energy spectrum was reconstructed with significant statistics up to 6 MeV, allowing, for the first time, to explore the completely unknown high excitation energy region. The highly segmented detection system allowed to also measure the angular distributions of the observed resonances at forward angles. The comparison with an extended mean-field approach, where the pairing correlations are introduced [7], allows to disentangle the s, p and d orbital contributions in the different portions of the energy spectrum. [1] H.Sagawa, B.A.Brown, H.Esbensen Phys. Lett. B 309 (1993) 1. [2] N.A.F.M.Poppelier, et al., Z.Phys. A 346 (1993)11. [3] H.G.Bohlen, et al., Z.Phys. A 344 (1993) 381. [4] H.B. Jeppesen et al. Phys. Lett. B 642 (2006) 449-454. [5] P. Santi et al. Phys. Rev. C 67 (2003) 024606. [6] T.Davison, et al., Nucl. Instr. And Meth. A 454 (2000) 350. [7] S.E.A. Orrigo and H. Lenske Phys.Lett. B 677 (2009) 214-220.

The investigation of neutron-rich dripline nuclei, including in particular those exhibiting haloes, is a central theme of present day nuclear structure physics. These studies have, however, been limited for the most part to the He, Li and Be isotopes. With the advent of the RIKEN RIBF and intense energetic beams of 48Ca, the way is now open to explore the structure of heavier neutron dripline nuclei. Here we describe investigations of the structure of the two heaviest candidate two-neutron halo systems, 19B and 22C, and the associated unbound sub-systems 18B and 21C, the level schemes of which are critical to the defining the 17B-n and 20C-n interactions for three-body models. In addition to being of direct importance to halo physics, 18,19B and 21,22C span the N=14 and 16 sub-shells closures below doubly magic 22,24O and are thus of considerable interest in terms of shell evolution far from stability. The measurements that will be described were carried out as part of the first phase of experiments employing the SAMURAI spectrometer and the NEBULA neutron array. Following a brief introduction to the setup and the analysis techniques, results for the invariant mass spectroscopy of 18B and 21C will be presented. In particular, those obtained using single and two-proton knockout -C(19C/20N,17B+n) and C(22N/23O,20C+n) - will be compared and contrasted with those derived from neutron knockout from 19B and 22C. The first results for the 17B+n and 20C+n transverse momentum distributions following neutron knockout will also be presented and conclusions drawn regarding the orbital angular momentum of the removed neutron.

Two-neutron halo nuclei have exotic structure in their ground states. Theoretically, their structure and binding mechanisms have been studied based on the core+n+n three-body model. From the three-body model calculation, the dineutron correlation, which is characterized as the spatially-correlated neutron pair, has been suggested in the ground states. In this work, we investigate the dineutron in two-neutron halo nuclei using the neutron-knockout reaction of 6He. We consider the neutron knockout from 6He with high momentum transfer, and discuss the possibility of direct measurement of dineutron in the ground state. In the reaction, the knocked-out neutron with high momentum transfer can be free from the final-state interaction, and hence, is expected to reflect the ground-state structure. However, due to the Borromean nature of 6He, the residual nucleus 5He decays with neutron emission. The emitted neutron mainly comes from the 5He(3/2-) resonance in the final state, and this sequential process might mask the ground-state information. In this contribution, we investigate the effect of the sequential process on the neutron-knockout reaction of 6He. We here calculate the angular correlation between the emitted neutrons, and discuss how to extract the information on the dineutron correlation from the observables.

During the past several tens of years, our knowledges about the features of exotic nuclei have been much enhanced. In 1980s, neutron halo structure of neutron drip-line nucleus, which is one of the most notable abnormal features of exotic nuclei, have been found. In 1990s, the vanishing of the N = 20 magic number for neutrons have been more extensively studied and discussed in so-called "island of inversion" region. In this presentation, precise reaction cross section data which have been recently measured at RIKEN, RI-beam Factory using BigRIPS fragments separator for 20-32Ne and 24-38Mg will be reported. The deformation features of Ne and Mg isotopes in the island of inversion and the possible "deformed halo" structure in 29, 31Ne and 37Mg will be presented from our data and the analysis with the microscopic double-folding model (DFM) and anti-symmetrized molecular dynamics (AMD) calculation.

Recent measurements of low-energy (quasi)elastic-scattering angular distribution of halo nuclei have shown a strong suppression of the Coulomb-nuclear interference peak [1]. Examining the components of the elastic-scattering differential cross sections for 11Be + 64Zn and 6He + 208Pb at energies near the Coulomb barrier [2], this appears to be caused by a dramatic phase-change (destructive) of the reduced Coulomb-nuclear interference term due to continuum couplings. [1] A. Di Pietro et al., Phys. Rev. Lett. 105 (2010) 022701; Phys. Rev. C 85 (2012) 054607. [2] A. Diaz-Torres and A. M. Moro, Phys. Lett. B 733 (2014) 89.

We report on an exploratory experiment performed with MINIBALL coupled to T-REX [1-2] at ISOLDE, to investigate neutron rich Sr and Y nuclei around mass A = 100, by cluster transfer reactions of neutron rich 98Rb/98Sr beams on a 7Li target. The aim of the experiment was on one hand to perform a γ-spectroscopy study by transfer reactions of neutron-rich Sr and Y nuclei beyond N=60 populated, so far, only via β-decay and spontaneous fission experiments [3]. On the other hand, we wanted to investigate the reaction mechanism exploiting weakly-bound nuclei in inverse kinematics by using radioactive beams. It has been shown that multi-nucleon transfer reactions represent a powerful tool to study neutron-rich nuclei and, in particular, cluster-transfer reaction can be used to populate exotic nuclei at medium-high spin and excitation energy [4]. 7Li is especially suitable for this purpose, since it has a pronounced cluster structure with an α and t as components. Owing to a separation energy of 2.5 MeV, it easily breaks up and one of the two fragments has a sizeable probability to be captured. In this work, for the first time, the combination of a radioactive beam with cluster transfer reactions is presented. This technique may turn out to be very useful in future and the present test experiment is meant as a first step of a research program aimed at spectroscopy studies of the low-lying structures of neutron-rich nuclei produced employing cluster-transfer reactions. In the experiment, a 98Rb beam, and a strong component of its β-daughter 98Sr, were accelerated at 2.85 MeV/A on a 1.5 mg/cm2 thick LiF target with an average intensity of 2x10^4 pps. The MINIBALL/T-REX [1-2] set-up allowed to detect the complementary charged particle emitted in coincidence with the γ-cascade of the excited system, giving a very clean trigger on the final populated residues. γ -rays have been detected after two or three evaporated neutrons and levels with spin up to 6 ħ have been observed. The reaction mechanism has been investigated by studying the cross section for both t and α transfer. Experimental results have been compared with theoretical calculations, performed by the FRESCO code [5], considering a one-step DWBA transfer of a cluster-like particle, showing that the model can predict with qualitative agreement the dynamics of the reaction and suggesting a proper description of the direct nature of the process. In conclusion, the present study shows that cluster transfer reactions can be consider as a valuable tool to study nuclear structure far from stability, encouraging their future application with new radioactive beam facilities of higher energy and intensity and with different weakly-bound target-nuclei. [1] N. Warr et al., EPJ, A(2013)49. [2] V. Bildstein et al., EPJ, A48(2012)85. [3] F. K. Wohn et al., PRL, 51(1983)873. [4] G. D. Darcoulis et al., JPG: Nucl.Part. Phys.23(1997)1191. [5] I. J. Thompson, Comp. Phys. Rep., 7(1988)167.

Nuclear break-up occurring at few tens of MeV per nucleon is an efficient tool to study clusterization into nuclei. A landscape of information extracted through nuclear break-up will be given. Firstly, pairing correlations can be studied. Pairing plays an important role to understand various aspect of nuclear physics but also nuclear astrophysics. Halo nuclei are the best place to study pairing effect in low-density matter. The case of 6He borromean nucleus was investigated at GANIL with an exclusive measurement in order to disentangle between the di-neutron and cigar configuration [1]. A theoretical reaction model going beyond mean-field was developed to understand the experimental data [2]. It shows very strong di-neutron contribution. Secondly, the alpha clusterization phenomenon was studied at GANIL in 40Ca and 40Ar to compare this effect in symmetric and asymmetric matter. The angular distribution of the emitted alpha particle are compared to Time Dependent Schrödinger Equation calculations to extract spectroscopic factors for the ground state [3]. No effect is observed on alpha clusterization when increasing the isospin asymmetry. According to AMD calculations, clusterization may show up in light nuclei close to the driplines. In the future, studies of isotopic chains up to the dripline are foreseen.

Many theoretical and experimental studies have been devoted to the cluster structure in nuclei in the past decades. But the detailed mechanism of clustering in nuclei is still an open question and is of fundamental importance in nuclear physics. For stable nuclei, the cluster structure is generally developed at excited states close to the corresponding particle decay threshold as illustrated in the Ikeda diagram. Nevertheless, when approaching the neutron drip line some compact cluster cores may be favored in exotic nuclei even in the ground state. Neutron rich Be isotopes are obvious good candidates of clustering studies, for the richness of their cluster structures built on a well established α+α rotor, and the N = 8 shell quenching in 12Be was proposed as a signal of α clustering. We have carried out a new breakup reaction experiment for 12Be at 29 MeV/nucleon at HIRFL-RIBLL in Lanzhou, China. A specially arranged detection system around zero degrees with high detection efficiency for states near the threshold was applied in this experiment. For the first time a strong resonance at around 10.3 MeV with a spin parity of 0+ was identified. And an enhanced monopole matrix element of about 7 fm2 and a large cluster decay width were also determined, in agreement with the GTCM calculation. These results reveal a strong clustering in the near threshold 10.3 MeV resonance in 12Be. Some other resonances were also observed in both 4He +8He and 6He+6He decay channels which are complementary to the previously suggested MR bands.

How important is the three-nucleon force (3NF)? This is one of the fundamental subjects in nuclear physics. This long-standing subject essentially started with the two-pion exchange 3NF proposed by Fujita and Miyazawa. For light nuclei, attractive 3NFs were introduced to reproduce the binding energies. In symmetric nuclear matter, the empirical saturation point could not be reproduced only with two-nucleon force (2NF) and then repulsive 3NFs were introduced. There is thus no doubt that the 3NF plays an important role in nuclear many-body systems. It is hard to define 2NF and 3NF clearly in a phenomenological way. This problem was solved by the chiral effective field theory (Ch-EFT), since it allows us to determine 2NF, 3NF and many-nucleon forces consistently and systematically. Recently, the roles of Ch-EFT 3NF have been analyzed in few-body systems and nuclear matter. In particular, the g-matrix interaction calculated from the Ch-EFT 2NF and 3NF well reproduce the saturation property in symmetric nuclear matter with no adjustable parameter. Microscopic description of nucleon-nucleus and nucleus-nucleus scattering is another important subject in nuclear physics. In particular, it is necessary to construct an accurate microscopic reaction theory for scattering of unstable nuclei, in which any phenomenological approaches based on optical potentials are not available. The scattering can be described by the g-matrix folding model with the local-density approximation. In the framework, the 3NF effects appear through the density dependence of the g-matrix. We aim to construct the microscopic reaction theory including the effects of Ch-EFT 3NF for scattering of stable and unstable nuclei. It is, however, not easy to construct a local form of the g-matrix interaction calculated from the Ch-EFT 2NF and 3NF, since the momentum cut-off is introduced. As an effective way of introducing the Ch-EFT 3NF effects, we modify the density dependence of the Melbourne g-matrix interaction constructed from the Bonn-B 2NF. This procedure is justified by the fact that in nuclear matter the g-matrix interaction calculated from the Bonn-B 2NF is close to that from the Ch-EFT 2NF. The Ch-EFT 3NF changes the folding potential less attractive and more absorptive, and consequently, the Ch-EFT 3NF yields better agreement with measured angular distributions of nucleus-nucleus elastic scattering.

MINOS is a new device composed of a thick hydrogen target and vertex tracker [1]. It has been primarily conceived for the spectroscopy of rare isotopes produced at fragmentation facilities such as the RIKEN Radioactive Isotope Beam Facility. In the near future, MINOS in association with other detectors and spectrometers should contribute to exciting physics programs at the RIBF focusing on nuclei produced by hydrogen-induced secondary knockout reactions. The full detector and its electronics have been finalized and validated at the end of 2013 and is now ready to run. Among foreseen experiments, a scientific program named SEASTAR dedicated to the study of shell evolution and measurement of new 2+ state energies in medium-mass unstable nuclei has been initiated at the RIBF. SEASTAR was initiated to exploit the unique opportunities offered by the RIBF and by use of the association of the high-efficiency DALI2 gamma array [2] and MINOS. The first campaign will be held in May 2014 with the aim to search for 2+ states of 78Ni and neighboring nuclei. A brief presentation of the MINOS detection system and main characteristics regarding (p,2p) reactions from in-beam validation at HIMAC will be made. The presentation will focus on the intended physics program at the RIBF and a report on the first SEASTAR campaign foreseen this spring. [1] A. Obertelli et al., Eur. Phys. J. A 50, 8 (2014). [2] T. Takeuchi et al., submitted to Nucl. Instr. Meth. Res. A (2014).

Fragmentation reactions induced by stable and unstable medium-mass and heavy projectiles have been systematically investigated at the Fragment Separator at GSI. The large isospin fluctuations characterizing this reaction mechanism explain the possibilities for extending the present limits of the chart of nuclides, in particular in the neutron-rich side. A particularly interesting channel, nucleon knock-out was carefully investigated using beams of stable and unstable tin isotopes between ${}^{110}$Sn and ${}^{132}$Sn. Glauber-type calculations point at the role of core excitations for the understanding the measured nucleon removal cross sections. For the most neutron-rich projectiles these excitations seem to be even beyond the single-particle picture. For the most neutron-deficient projectiles the role of core excitations change from the neutron to the proton sector, in agreement with similar measurements obtained at RIKEN using beams of ${}^{104}$Sn and ${}^{112}$Sn [1] [1] L. Audirac et al., PRC 88, 041602 (2013)

The occurrence of a central density depletion (“bubble”) has been predicted by Mean Field and Relativistic Mean Field calculations in several parts of the chart of nuclides, including in particular superheavy nuclei [1][2]. Such a drop in the central density is very rare and has not yet been observed experimentally. Bubble nuclei could constitute a useful tool to test the spin-orbit interaction, this term being linked with the derivative of the nuclear density. In order to highlight the bubble phenomenon, an experiment was performed at NSCL in September 2012. The 34Si(-1p)33Al reaction was used to determine the proton 2s1/2 occupancy in 34Si. At the same time the 36S(-1p)35P reaction was performed. The results concerning 34Si will then be compared to those obtained for 36S, the occupancies of which are already known from a 36S(d,3He)35P experiment [3]. The S800 spectrometer was used to determine the parallel momentum distribution of the knock-out residues and then determine the orbital quantum number l of the residual nuclei. The high efficiency, high resolution gamma array GRETINA was used to tag the feeding of excited states in the knock-out residues and then determine the proton 2s1/2 occupancy of the incident nuclei. 34Si was chosen as a good candidate for a proton bubble, as the 34Si(d,p)35Si experiment performed at GANIL in 2009 revealed a significant change in the spin-orbit splitting of this nucleus [4], which suggests it has an anomalous density profile. Moreover its proton 2s1/2 occupancy has been predicted to be quite low (S=0.08), which is a key criterion for bubble occurrence, since only l=0 orbitals contribute to the central nuclear density. The 2s1/2 occupancy constitutes then a useful and more direct probe for bubble phenomena. Motivations for studying bubble phenomena will be introduced, and the experimental setup as well as the current state of the analysis will be detailed. [1] M. Grasso, L. Gaudefroy, E. Khan et al., Phys. Rev. C 79 (2009). [2] J. Dechargé, J.-F. Berger, M. Girod, K. Dietrich, Nucl. Phys. A 716 (2003) 55. [3] S. Khan et al., Phys. Lett. B156, 155 (1985). [4] G. Burgunder et al., Phys. Rev. Lett. 112, 042502 (2014).

We hereby address selected experiments at the R3B-LAND setup (at GSI in Darmstadt, Germany), dedicated to investigations of nuclear structure with proton-induced quasi-free scattering reactions in inverse kinematics at relativistic energies. Kinematically complete measurements were undertaken, which allow for analysis of (p,2p) and (p,pn) reactions. Similar technique with an upgraded setup will be used for the future R3B program at FAIR/GSI, for studies of the single-particle structure and the role of N-N correlations in very exotic nuclei. The QFS signature of the studied reactions has been observed by angular correlations of the knocked out nucleon and the recoiled target proton at large scattering angles. Cross sections for knocking out a proton/neutron from corresponding single-particle states have been measured. In combination with a reaction theory, they provide information on the reduction of spectroscopic strength for relevant states. Momentum distributions of the projectile-like reaction fragments are also reconstructed and compared to model calculations. The discussion will include a benchmark case of quasi-free knockout reactions on 12C as well as the neutron-deficient 11C, 10C isotopes. Measurements of nucleon knockout to different final bound states, using in-flight gamma-ray spectroscopy, and the possibility of studying deeper lying states with the invariant mass method will be presented. It will be followed by a discussion of an experiment with the Oxygen isotopic chain (14O to 24O), allowing for systematic studies of the spectroscopic strength within a wide range of isospin asymmetry. Six isotopes have been analyzed so far and the preliminary results will be presented. Additionally, we will report on measurements of the proton- and neutron- spectroscopic strengths in the heavier, unstable 57Ni nucleus. The deduced spectroscopic / reduction factors will be compared to the existing data in literature. The work is supported by the German Federal Ministry for Education and Research (BMBF project 05P12RDFN8), by HIC for FAIR and by GSI-TU Darmstadt Cooperation Contract.

The description of nuclei starting from the constituent nucleons and the realistic interactions among them has been a long-standing goal in nuclear physics. In addition to the complex nature of nuclear forces with two-nucleon, three-nucleon and possibly even four-nucleon components, one faces the quantum-mechanical many-nucleon problem governed by an interplay between bound and continuum states. In recent years, we have made a significant progress in developing ab initio many-body approaches capable of describing both bound and scattering states in light nuclei simultaneously employing two- and three-nucleon forces from chiral effective field theory. We will present calculations of resonances of exotic nuclei 7,9He, 11N, scattering of 10C and 8He on protons, structure of the neutron rich 17C. Further, we will discuss our efforts to describe (d,p) and (d,n) transfer reactions within our ab initio framework.

Nucleosynthesis of light nuclei is an important problem in nuclear astrophysics. The radiative three-body capture processes, such as the triple alpha process, have been described traditionally as two-step sequential reactions. However, it has been shown in the recent years that the direct three-body recombination may play an important role in describing the reaction rates for the entire temperature range relevant in astrophysics. At the helium burning stage of stars, the triple alpha reaction for the formation of 12C is the main nucleosynthesis process overcoming the instability gaps at mass numbers A=5 and A=8. At low temperatures, where sequential models fail, the reaction rate of such process is still an open problem in nuclear astrophysics. This problem also applies to neutron rich environments, where the formation of 6He (alpha + n + n) and 9Be (alpha + alpha + n) has been linked to the nucleosynthesis by rapid neutron capture (r-process) in type II supernovae. Other important processes may occurr in different astrophysical scenarios. In a binary system that consists of two stars, a normal star (main sequence or red giant) and a compact object such as a neutron star, the transfer of H-rich material from the normal star to the neutron star provides an ideal medium for nucleosynteshis through rapid proton capture (rp-process). Among the rp-process appears the formation of 17Ne (15O + p + p). The interest of this reaction arises from the fact that 15O is a waiting point in the CNO cycle, and this rp-process can bridge towards the production of heavier elements. The description of three-body capture reactions requires a complete three-body formulation of the system. The complete computation of this reactions in the whole energy range requires a narrow grid of continuum or scattering states right above the breakup threshold, which is a difficult task. The asymtotic behavior of continuum states for system with several charged particles is not known in general, and very involved procedures are needed to deal with this problem. We show a pseudo-state method, called the analytical transformed harmonic oscillator (THO) method, as a continuum discretization approach to describe the above mentioned three-body capture reactions. The THO basis is generated with an analytical local scale transformation of the harmonic oscillator functions, and the parameters of the transformation govern the density of PS at a given energy, allowing the construction of an optimal basis for each observable of interest. Our method describes both bound and continuum (resonant and non-resonant) states of the system in a full three-body quantum formalism without requiring the previous knowledge of the continuum asymptotic behavior. We have successfully applied the formalism to the nucleus 6He [PRC 88 (2013) 014327]. Calculation on 9Be, 12C and 17Ne are in progress.

The structure of nuclei at and beyond the proton-drip line is very interesting as they show very attractive features such as halo structures, mirror symmetry breaking and narrow resonances in the continuum. In addition, they are important in the understanding of the rapid proton capture nucleosynthethic process (rp process). Knowledge of the nuclear properties in the light proton drip line region are key inputs to network calculations of the rp-path. However, little spectroscopic information is known about the structure of 25P which is proton unbound. Up to now only an upper limit of the lifetime of the unbound ground state has been measured [1]. Here we present the asymptotic normalization coefficients (ANCs) for mirror states in 25P obtained from the neutron transfer reaction 24Ne(d,p)25Ne at 10.6 AMeV [2] and using proton resonance energies obtained from a two-body potential approach. Preliminary results from the analysis shows that the neutron stripping to the states of 25Ne is rather peripheral enabling the prediction of proton widths in 25P using the mirror symmetry. [1] http://www.nndc.bnl.gov; G. Audi et al, Nucl. Phys. A 729, 337 (2003). [2] W.N. Catford et al. Phys. Rev. Lett. 104 19 (2010) .

The structure of 12C, and especially the nature of its excited states above the three-alpha threshold, is still one of the most actively investigated questions in nuclear physics. In this talk we extend our previous studies of the Hoyle state obtained in bound state approximation and focus on the structure of the resonances and the continuum above the three-alpha threshold. Results of the microscopic alpha-cluster model with Volkov and Minnesota forces are compared with results in the fermionic molecular dynamics (FMD) approach, where individual nucleons are considered as degrees freedom. For the FMD calculations an effective realistic interaction derived in the unitary correlation operator method (UCOM) is employed. We describe the continuum by explicitly coupling the internal region with 8Be+alpha channels in the external region, including both the narrow ground state of 8Be and excited 0+, 2+ and 4+ pseudo states obtained by diagonalization in a large box. The 12C resonance parameters and 8Be-alpha scattering phase shifts are obtained with the microscopic R-matrix method. Of particular interest are the properties of the second 0+ state, the famous Hoyle state, and the second 2+ state. Monopole and quadrupole transition strengths are analyzed and compared to experiment.

Characterizing the nature of single-particle states outside of double shell closures is essential to a fundamental understanding of nuclear structure. This is especially true for those doubly magic nuclei that lie far from stability and where the shell closures influence nucleo-synthetic pathways. The region around 100Sn is one of the most important due to the proximity of the N=Z=50 magic numbers, the proton-drip line, and the end of the rp-process. However, owing to the low production rates, there is a paucity of spectroscopic information and no firm spin-parity assignment for ground states of odd-A isotopes close to 100Sn. Neutron knockout reaction experiments on beams of 108,106Sn have been performed at the NSCL. By measuring gamma rays and momentum distributions from reaction residues, the spins of the ground and first excited states for 107,105Sn have been established. The results also show a degree of mixing in the ground states of the isotopes 108,106Sn between the d5/2 and g7/2 single particle-states. Momentum distributions, compared to Eikonal-model reaction calculations, and cross sections will be presented.

This talk would present a systematic study of knockout reactions from projectiles with a large difference in separation energies between valence neutrons and protons. We have taken into account kinematical effects on the shapes of the spectra as well as on the cross sections. We will also show how to take into account the no-breakup of the weakly bound particle when the deeply bound particle is knocked out.

The elucidation of the so-called “island of inversion” (Z ~ 10-12, N ~ 20-22) is one of the most important subjects in current nuclear physics. Since nuclei in the region have exotic properties that never appear in stable nuclei, it is important to understand them properly through the microscopic framework with no free parameter. In the previous works [1, 2], interaction cross sections σI measured for 28-32Ne [3] were analyzed by the double folding model with the densities calculated by antisymmetrized molecular dynamics (AMD). This fully microscopic framework, which never assumes structure of the nuclei, reproduces the measured σI with no adjustable parameter, and concludes that 28-32Ne have large deformation and in particular 31Ne is a deformed halo nucleus. In this study, we apply the microscopic framework to 24-40Mg (N = 12-28) and determine the ground-state properties (spin-parity, total binding energy, deformation and radius) from reaction cross sections measured very lately at the Radioactive Ion Beam Factory (RIBF) [4]. The AMD calculations, which predict large deformation for all the Mg isotopes, succeed in reproducing the measured reaction cross sections overall. For 37Mg as a new candidate of deformed halo nucleus, however, the AMD calculation considerably underestimates the data, even though the predicted deformation is fairly large. This result suggests that 37Mg is a deformed halo nucleus and hence the tail correction should be made for the AMD density with the resonating group method. We will discuss the point in the presentation. Furthermore, the AMD calculations predict large deformation for 24-40Mg (N = 12-28). This prediction is supported by the fact that the E(4+)/E(2+) ratios for 34,36,38Mg deduced by in-beam γ-ray spectroscopy are about 3.1 independently of N [5]. These results suggest that not only the N = 20 magicity but also the N = 28 magicity disappears in the region. [1] K. Minomo et al., Phys. Rev. Lett. 108, 052503 (2012). [2] T. Sumi et al., Phys. Rev. C 85, 064613 (2012). [3] M. Takechi et al., Phys. Lett. B 707, 357 (2012). [4] M. Takechi et al., submitted to Phys. Rev. Lett., to be published in EPJ Web of Conferences. [5] P. Doornenbal et al., Phys. Rev. Lett. 111, 212502 (2013).

The R³B reaction setup provides a high-class versatile and flexible tool for all kind of reaction studies. The main features of the setup will be brought in conjunction with the related physics cases. The related technical challenges in detector and accelerator science will be addressed. Cross links to other proposed setups at the future facility will be outlined and the presumed schedule for its realization will be discussed.

Spectroscopic factors (SF) are fundamental quantities in nuclear physics. They have been extensively used in understanding the single particle properties of nuclear structures. In this talk, I will discuss the spectroscopic information extracted for the 4 hole-states (f7/2, p3/2, s1/2 and d3/2) of 45Ar, 47Ca, 49Ti, 51Cr, 53Fe and 55Ni, all with N=27. The H(46Ar,d)45Ar and H(56Ni,d)55Ni reactions were studied in inverse kinematics at the Coupled Cyclotron Facility at Michigan State University with the high resolution silicon array HiRA and the S800 spectrometer. Spectroscopic information of the other nuclei were extracted from the published experiments using normal kinematics of (p,d) transfer reactions. The compiled data shows the evolution of the single-particle states from stability to instability regions. Of especial interest are the deep hole-states of s1/2 and d3/2 below the Fermi Energy. Successful description of these states must include nucleonic orbits in both the sd and pf shells. Thus the present set of data provides a benchmark for large basis calculations that require effective interactions between the sd and pf orbits. Results from using different state-of-the art models to reproduce the excitation energies and spectroscopic factors will be presented.

G.Cardella1, N.Keeley10, L.Acosta2, F.Amorini2, L.Auditore4, I.Berceanu8, M.BChatterjiee9, E.DeFilippo1, L.Francalanza2,3, L.Grassi1,3, E.La Guidara1,7, G.Lanzalone2,5, I.Lombardo2,6, T.Minniti4, E.V.Pagano2,3, M.Papa1, S.Pirrone1, G.Politi1,3, F.Rizzo2,3, E.Rosato6, P.Russotto2,3, A.Trifirò4, M. Trimarchi4, G.Verde1, M.Vigilante6 1 INFN - Sezione di Catania, Via S. Sofia, 95123 Catania, Italy 2 INFN - Laboratori Nazionali del Sud, Via S. Sofia, Catania, Italy 3 Dip. di Fisica e Astronomia, Università di Catania, Via S. Sofia, Catania, Italy 4 INFN Gruppo collegato di Messina & Dip. di Fisica, Università di Messina, Italy 5 Facoltà di Ingegneria e Architettura, Università Kore, Enna, Italy 6 INFN Sezione di Napoli & Dipartimento di Fisica, Università Federico II, Napoli, Italy 7 Centro Siciliano di Fisica Nucleare e Struttura della Materia, Catania, Italy 8 Institute for Physics and Nuclear Engineering, Bucharest, Romania 9 Saha Institute for Nuclear Physics, Kolkata, India 10 National Centre for Nuclear Research, Świerk, Poland Neutron rich exotic beams (6He, 8,9Li, 10,11Be, 13B, 16,17C), produced through the in-flight fragmentation of 18O beams at 55 A•MeV, are available at LNS [1]. Using the CHIMERA detector [2,3], we have begun a campaign to study transfer reactions with proton- and deuteron-rich targets. The kinematical coincidence method was used to extract high resolution angular distributions of binary reactions from the measured light particle energy spectra [4]. A reproduction of the data of the 10Be+p,d9Be+d,t reactions was obtained using CRC calculations and the results compared with a recent analysis of lower energy data [5]. Complementary information from the -ray detected in the CsI stage of the CHIMERA detectors was also used to disentangle the ground state from excited levels in the final stage of the reaction. Perspectives on future measurements with the use of the new FARCOS array [6] and on upgrading the intensity of the fragmentation beam will also be given. References: [1] see http://fribs.lns.infn.it/upgrade-results.html [2] A.Pagano et al, Nucl. Phys. A 734 (2004) 504 [3] A.Pagano, Nuclear Physics News International, 22:1(2012)25. [4] L.Acosta et al, NIM A 715 (2013) 56. [5] N. Keeley, K. W. Kemper and K. Rusek, Phys. Rev. C 86, 014619 (2012). [6] G.Verde et al, Journal of Physics: Conference Series 420 (2013) 012158.

We present spectroscopic information provided in single nucleon transfer reactions on the valence shells of nuclei with very large neutron/proton asymmetry. The cross sections for nucleon removal were compared to shell model predictions. The weak dependence on asymmetry contrasts with results of knock-out experiments at higher incident energy. The neutron deficient 14O has been first investigated. Both the single neutron and proton pick-up cross sections from a deuterium target were measured with the MUST2 array coupled to the magnetic spectrometer VAMOS at GANIL and the 14O SPIRAL beam at 18 MeV/nucleon. 14O with a large neutron/proton asymmetry ΔS = |Sn-Sp | ~ 18 MeV is a good candidate to study the evolution of the cross sections for the transfer of valence nucleons in deeply or weakly bound orbitals. Previous results obtained in direct kinematics with 16O and 18O were included in the data set. Different prescriptions for the form factors (Saxon Woods and ab-initio form factors) have been used and tested. The sensitivity on the final results will be shown.

In two (d,3He) transfer reactions with MUST2 at Ganil and the split-pole at Orsay, we have determined the position of the proton-hole states in the neutron-rich 71Cu and 69Cu isotopes (Z = 29, N = 42 and 40). We have found that in 71Cu the hole strength of the f7/2 orbital lies at higher excitation energies than expected. From β-decay, the f5/2 excited particle state in these isotopes was known to come down rapidly in energy when passing N = 40 [1] and even become the ground state in 75Cu (N = 46) [2]. This sudden energy shift has been explained in a number of theoretical works [3,4,5]. The prediction for the f7/2 spin-orbit partner was that it would lower in energy as well through a related effect. The present result, however, indicates a decorrelated behaviour between the spin- orbit partners. We remeasured the single-particle strength in 69Cu in the corresponding (d,3He) reaction in order to extend the existing data [6] and in particular to make sure that there is a consistent analysis of spectroscopic factors between both isotopes. Taking together the results from both reactions, we find that additional mechanisms may have to be included to understand the nuclear structure of the neutron-rich copper isotopes and constrain the weakening of the Z = 28 shell gap towards doubly magic 78Ni. [1] S. Franchoo et al., Phys. Rev. Lett. 81, 3100 (1998) [2] K. Flanagan et al., Phys. Rev. Lett. 103, 142501 (2009) [3] K. Sieja and F. Nowacki, Phys. Rev. C 81, 061303(R) (2010) [4] N. Smirnova et al., Phys. Rev. C 69, 044306 (2004) [5] T. Otsuka et al., Phys. Rev. Lett. 97, 162501 (2006) [6] B. Zeidman and J.A. Nolen, Phys. Rev. C 18, 2122 (1978)

The Modular Neutron Array (MoNA) in conjunction with the large-gap Sweeper magnet at the NSCL is an effective setup to explore neutron-unbound states. The recent addition of the Large-area multi-Institutional Scintillator Array (LISA) increased the efficiency and acceptance for the neutron detection. Neutron-unbound nuclei beyond the dripline as well as neutron unbound excited states of bound nuclei have been populated using primarily proton removal reactions. The (d,p) reaction in inverse kinematics with a secondary 14Be beam on a CD2 target was used for the first time to measure 15Be. Results of other recent experiment including 10He, 10,12,13,Li, 12,13Be, and 19,21C will be presented.

Unbound nuclei, at the border between bound nuclear systems and the continuum, offer a unique way to increase understanding of the nuclear interaction. Radioactive ion beams at high energies provide the possibility to create and study unbound nuclei using e.g. knock-out reactions. These reactions imply little interaction with the spectator part of the nucleus and are thus a versatile tool for spectroscopy. The present work is based on an experiment performed in 2010 using the LAND/R3B setup at GSI. Secondary beams with an energy around 450 AMeV in the Z = 4 to Z = 10 region were employed. This multipurpose experiment aimed not only at the study of unbound nuclei using proton knock-out reactions but also on single-particle spectroscopic factors, the shell structure of neutron rich nuclei and (n,gamma)-rates of astrophysical relevance in this region of the nuclear chart. The LAND/R3B setup allows for event-by-event detection in complete kinematics having an almost 4 acceptance due to the relativistic forward-focusing of the reaction-products. It is therefore ideal for studying unbound nuclei using proton knock-out reactions. In particular the unbound nuclei 16B and 13Be, produced by proton knock-out from 17C and 14B respectively, are the subject of this work. The relative energy of the bound core + neutron systems is studied as well as their gamma-spectra,yielding information about the orbital momenta of the unbound systems.

Interpretation of the properties of unbound nuclei is one of the most important subjects in nuclear physics. In this paper we focus on 21C formed by the transfer reaction 20C(d,p)21C. In this reaction 21C (the n+20C system in fact) with various energy states, which can be the d3/2 resonance or nonresonant continuum states, are populated by the neutron transfer to 20C. We describe the coupling between those states by using the continuum-discretized coupled-channels method (CDCC). CDCC is a powerful reaction model which can treat explicitly the coupling between bound states and continuum states including resonances. It is well known that the transition matrix of a transfer process populating an unbound nucleus diverges. In this study, we circumvent this problem by choosing carefully the transition interaction for the transfer reaction. The purpose of this study is to investigate how the coupling between resonant and nonresonant states is strong, and see its effects on the transfer cross section. This cross section brings the energy spectrum of the n-20C system, which will reveal the "figure" of 21C formed by the 20C(d,p) reaction.

Tetra-neutron systems in nuclei have attracted considerable attention since candidates of bound tetra-neutron system were reported[1]. While later theoretical paper using ab- initio calculations[2] suggest that bound tetra-neutron cannot exist, the possibility of the tetra-neutron system forming a resonance state is still an open and fascinating question. We performed missing-mass spectroscopy of the 4n system via the exothermic double- charge exchange reaction 4He(8He,8Be)4n. The experiment was carried out at the RI Beam Factory (RIBF) at RIKEN using the SHARAQ spectrometer and liquid He target system. The secondary beam, 8He at 190A MeV, had a large internal energy, it was possible to produce the 4n system in small momentum transfers of less than 20 MeV/c. To obtain the missing-mass spectrum, we measured momentum of the 8He beam with the High-Resolution Beamline and momentum of two alpha particles which were the decay products of the 8Be projectile, with the SHARAQ spectrometer. In the present analysis, a method for treating multi-hits in Multi-Wire Drift Chambers (MWDCs) under high beam rate condition (2 MHz) was developed for good statistics. At focal plane Cathode Readout Drift Chamber (CRDC), 8Be can identified by measuring the invariant mass of the coincident two-alpha particle with a good signal-to-noise ratio. We can be identified about a hundred candidate events for 4n system. We will show the preliminary result of missing-msss spectrum and evaluation of the cross section.

The symmetry energy term of the nuclear equation-of-state, describing fundamental phenomena both in nuclear physics and in astrophysics, is the focus of huge theoretical and experimental efforts. The electric dipole response of nuclei as a function of the neutron-to-proton-asymmetry is driven by the symmetry energy and in particular by its density dependence. Studies of the Pygmy Dipole Resonance (PDR) in exotic nuclei have been used to constrain the symmetry energy or the neutron skin thickness. The electric dipole polarizability αD, being very sensitive to the low-lying dipole strength, is correlated to the neutron skin thickness in a robust and less model-dependent manner [1]. Recently, for the stable nucleus, 208Pb the neutron skin thickness was extracted from the measured αD [2]. Here, a first experimental determination of the electric dipole polarizability αD in an unstable nucleus, namely 68Ni, and the derivation of its neutron-skin thickness will be reported [3]. Coulomb excitation in inverse kinematics at the R3B-LAND setup at GSI allows for the investigation of the dipole strength distribution in the neutron-rich 68Ni with excitation energies spanning the pygmy (PDR) and giant dipole resonance (GDR). The results comprise the resonance parameters for the observed PDR at 9.55(17) MeV and the GDR at 17.1(2) MeV. In combination with the results from Wieland et al. [4] an unexpectedly large direct photon-decay branching ratio of 7(2)% is observed for the PDR. The measured αD of 3.40(23) fm3 is compared to relativistic RPA calculations [5] yielding a neutron-skin thickness of 0.17(2) fm for 68Ni. [1] P.-G. Reinhard and W. Nazarewicz, Phys. Rev. C 81, 051303 (2010). [2] A. Tamii et al., Phys. Rev. Lett. 107, 062502 (2011). [3] D. Rossi et al., Phys. Rev. Lett. 111, 242503 (2013). [4] O. Wieland et al., Phys. Rev. Lett. 102, 092502 (2009). [5] J. Piekarewicz, Phys. Rev. C 83, 034319 (2011).

Through the studies of the structure and spectroscopy of the neutron-rich nuclei along extended isotopic chain towards the drip-line, we can develop our understanding of the evolution of the nuclear structure with the isospin degree of freedom and of the modeling of the nuclear correlations. Experimentally the neutron drip-line is known up to the oxygen chain, with 24O being the last bound isotope. Drip-line nuclei combine several aspects which correspond to new phenomena, as compared to the stable isotopes, like low particle threshold energies, very diffuse nuclear surfaces, resonant states, new shell gap effects associated to local magic numbers [1-3]. Today, there exists no unified theoretical framework able to describe consistently the structure properties of these nuclei. They are weakly-bound with few, or no bound excited states, and the coupling to the continuum is playing a significant role since the scattering states are much closer to the continuum states than in stable nuclei. All these aspects are stringent tests for the microscopic structure calculations, and the drip-line nuclei appear as benchmarks for the nuclear models including the effects of the 3-nucleon forces [4-6]. In the region of the neutron-rich nuclei around 24O, the new N=16 shell closure has been discussed [2,3] and theoretically interpreted as due to the enhancement between 2s1/2 and 1d3/2 shells [3]. The properties of the 24O nucleus have been intensively studied. 24O having no bound excited state, its spectroscopy was measured using invariant mass method at MSU [7] and recently at RIKEN [8]. They have both discussed new excited states; the 2+ deformation was studied in Ref. [8], confirming the picture of the N=16 doubly-magic nucleus. In the same period, we used another technique to investigate the structure and the spectroscopy of 24O via proton elastic and inelastic scattering (p,p’) and the missing mass method. The experiment was performed at RIKEN in the BigRIPS line, using a high intensity beam of 24O (mean intensity 1700/s) produced at RIBF at 263 MeV/n, and the state-of-the-art charged particle detector MUST2 [9]. The (p,p’) excitation energy spectrum of 24O was deduced but the 2+ state above the Sn (4.19 MeV) could not be observed due to the very low statistics for the inelastic events. However, new states above S2n (6.9 MeV) are indicated, with the possible E1 transition strength located around 9 MeV. In this talk we will discuss the characteristics of these states and compare them to various microscopic calculations, with large scale Shell Model [10] or within QRPA [11]. For the proton elastic scattering of the 21-24O isotopes, we have obtained enough statistics; the angular distributions will be presented. These results constitute a unique benchmark to explore the characteristics of the proton-nucleus interaction potential around 260 MeV/n. We will discuss the validity of the microscopic reaction framework based on the G-matrix density-dependent potentials [12] and of the structure inputs [11]. [1] T. Motobayashi et al., Phys. Lett. B 346, 9 (1995). [2] A. Ozawa et al., Phys. Rev. Lett. 84, 24 (2000). [3] T. Otsuka et al., Phys. Rev. Lett. 87, 082502 (2001). [4] T. Otsuka et al., ibid 105, 032501 (2010). [5] J. D. Holt, J. Menendez, A. Schwenk, arXiv:1108.2680, Eur. Phys. J. A 49, 39 (2013). [6] G. Hagen et al., Phys. Rev. C 80, 021306(R) (2009); G. Hagen et al., PRL 108, 242501 (2012). [7] C. R. Hoffman et al., Phys. Lett. B 672, 17 (2009). [8] K. Tshoo et al., Phys. Rev. Lett. 109, 022501 (2012). [9] E. C. Pollacco et al., Eur. Phys. J. A 25, s01, 287 (2005). [10] H. Sagawa and T. Suzuki, Phys. Rev. C 59, 3116 ( 1999). [11] M. Martini, S. Péru and M Dupuis, Phys. Rev. C 83, 034309 (2011). [12] M. Dupuis et al. Phys. Rev. C 73, 014605 (2006).

EXL (EXotic nuclei studied in Light-ion induced reactions at the NESR storage ring) is a project within NUSTAR [1] at FAIR [2]. It aims for the investigation of light-ion induced direct reactions in inverse kinematics with radioactive ions cooled and stored in the future NESR (New Experimental Storage Ring). A universal detector system will be built around an internal target of the NESR in order to detect the target-like recoils. One of the key interests of EXL is the investigation of reactions at very low momentum transfers where, for example, the nuclear matter distribution, giant monopole resonances (GMR) or Gamow-Teller transitions can be studied [3]. The existing ESR (Experimental Storage Ring) at GSI, together with its internal gas-jet target, provides a unique opportunity to perform this kind of experiments on a smaller scale already today. In the last years we have developed a UHV compatible detector setup based on DSSDs (Double-sided Silicon-Strip Detector) as well as lithium-drifted silicon pad detectors for the target-like recoils [4] and an in-ring detection system for the projectile like heavy ions. With this setup we were able to successfully investigate reactions with a stored radioactive beam for the first time ever. As a part of the first EXL campaign we investigated the reaction 56Ni(p,p)56Ni by measuring the differential cross section for elastic proton scattering and for determining the nuclear matter distribution of 56Ni. This contribution will present the current status of the project and preliminary results. This work was supported by BMBF (06DA9040I and 05P12RDFN8), the European Commission within the Seventh Framework Programme through IA-ENSAR (contract no. RII3-CT-2010-262010), HIC for FAIR and TU Darmstadt-GSI cooperation contract. [1] http://www.fair-center.eu/for-users/experiments/nustar.html [2] http://www.fair-center.eu [3] H.H. Gutbrod et al. (Eds.), FAIR Baseline Technical Report, ISBN-3-9811298-0-6, Nov. 2006 [4] B. Streicher et al, Nucl. Instr. And Meth. A 654 (2011) 604

Single nucleon knockout and quasi-free scattering reactions are valuable tools to study single-particle properties of nuclei [1]. Particularly, it has been argued, that they can be used to study spectroscopic factors on an absolute scale [2]. Quenching of these spectroscopic factors as compared to shell-model predictions has been observed in nuclear knockout reactions [3]. While for stable isotopes these findings are in agreement with results obtained in quasi-free electron scattering [1,4], a surprisingly large dependency of this quenching on the neutron-proton asymmetry has been observed, motivating further studies using quasi-free proton scattering. Quasi-free scattering from the neutron-deficient carbon isotopes 10C and 11C has been studied in inverse kinematics during experiment S393 at GSI. A 40Ar beam, accelerated to 490AMeV by the SIS18 heavy ion synchrotron, was incident on a production target at the entrance of the fragment separator FRS, and the resulting cocktail beam including 10C and 11C was then transported to the R3B-LAND setup. Here, the incoming beam as well as all reaction products were detected in a kinematically complete measurement. Results for the cross sections and associated spectroscopic factors as well as the momentum distributions of reaction products for the reactions 11C(p,2p), 11C(p,pn) and 10C(p,pn) will be shown and compared to results obtained for knockout reactions as well as calculations with distorted wave impulse approximation. Furthermore, excitation spectra of the reaction products will be discussed. [1] G. Jacob and Th. A. J. Maris Rev. Mod. Phys. 38 (1966) 121 [2] B. A. Brown et al., Phys. Rev. C 65 (2002) 061601 [3] A. Gade et al., Phys. Rev. C 77 (2008) 044306 [4] G. J. Kramer, H. P. Blok, and L. Lapikas, Nucl. Phys. A 679 (2001) 267 Supported by the State of Hesse (LOEWE Centre HIC for FAIR), and through the GSI-TU Darmstadt cooperation agreement.

Quasi-free knock-out reactions are a direct tool to study the occupancy and the location of valance and deeply bound single particle states. Recent experiments have showed a reduction of spectroscopic strengths of about 60-70% for stable nuclei. When going to driplines this tendency is changing , loosely bound nucleons have spectroscopic strengths close unity while deeply bound nucleons have a large reduction of the spectroscopic strength. We want to make a systematic study of spectroscopic factors of the Oxygen isotopic chain using quasi-free (p,2p) and (p,pn) knock-out reactions in inverse kinematics. This will allow us a qualitative and quantitative understanding of spectroscopic factors in a large variation of isospin asymmetry. For this we performed an experiment at the R3B/LAND setup at the GSI Facility in 2010 with a secondary beam from 14^O to 24^O at the energies around 400-500 MeV/u. Six isotopes have been analyzed so far and the preliminary results will be presented. The results include the partial cross sections, gamma ray spectra of the residual fragments in coincidence, and their spectroscopic strengths. This work is supported by HIC for FAIR and BMBF project 05P12RDFN8.

Coulomb breakup of nuclei away from the valley of stability have been one of the most successful probes to unravel their structure. However, it is only recently that one is venturing into medium mass nuclei like 23O [1] and 31Ne. This is a very new and exciting development which has expanded the field of light exotic nuclei to the deformed medium mass region. In this contribution we report a very recent extension of theory of Coulomb breakup within the post-form finite range distorted wave Born approximation to include deformation of the projectile [2]. The electromagnetic interaction between the fragments and the target nucleus is included to all orders and the breakup contributions from the entire non-resonant continuum corresponding to all the multipoles and the relative orbital angular momenta between the fragments are taken into account. Only the full ground state wave function of the projectile, of any orbital angular momentum configuration, enters in this theory as input, thereby making it free from the uncertainties associated with the multipole strength distributions that may exist in many of the other theories. We shall identify reaction observables, which are 'prone' to deformation effects of the projectile by studying the breakup of 31Ne on Pb and Au at 234 MeV/u, and compare our results with the available data. New results on the breakup of 37Mg - a possible halo candidate- will also be presented. Finally we shall outline our efforts in the construction of a breakup theory, under the post-form reaction theory formalism, where one includes the continuum to all orders. We shall also consider including relativistic effects, which are bound to appear for incident beam energies ranging from 200-1000 MeV/u - a range very relevant for GSI, RIKEN and other facilities. References [1] R. Chatterjee, R. Shyam, K. Tsushima, A. W. Thomas, Nucl. Phys. A (vol. 913), 116 (2013). [2] Shubhchintak and R. Chatterjee, Nucl. Phys. A (vol 922), 99 (2014).

Time-dependent density functional theory can be viewed as an exact reformulation of time-dependent quantum mechanical problem, where the fundamental variable is no longer the many-body wave-function but the density. For systems like atomic nuclei and quantum atomic gases this approach has to be extended in order to deal with superfluid fermionic systems. Within the framework of the unrestricted time-dependent density functional theory, we present for the first time an analysis of the relativistic Coulomb excitation of the heavy deformed open shell nucleus 238U. The approach is based on Superfluid Local Density Approximation (SLDA) formulated on a spatial lattice that can take into account coupling to the continuum, enabling self-consistent studies of superfluid dynamics of any nuclear shape. We have computed the energy deposited in the target nucleus as a function of the impact parameter, finding it to be signicantly larger than the estimate using the Goldhaber-Teller model. The isovector giant dipole resonance, the dipole pygmy resonance and giant quadrupole modes were excited during the process. The one body dissipation of collective dipole modes is shown to lead a damping width of about 0.4 MeV and the number of pre-equilibrium neutrons emitted has been quantified.

The nuclei far from beta-stability often exhibit exotic properties, such as shell-gap quenching and large nuclear deformation. An appearance of anomalous parity intruder states at a low excitation energy region, for example, will provide a clue to identify the phenomena. The present study focuses on low-lying negative parity states in 17C above the neutron decay threshold. In the neighboring 16C nucleus, the lowest-lying negative parity state was detected at a relatively high excitation energy of Ex = 5.45(1) MeV (Y. Satou et al., Phys. Lett. B 728, 462 (2014)). In 17C, on the other hand, the lowest-lying negative parity state is expected to be located at a much lower excitation energy region. A shell-model calculation suggests the presence of the first 1/2- state at Ex = 0.783 MeV (E. C. Simpson et al., Phys. Rev. C 79, 024616 (2009)). Ueno et al. have observed a lowest-lying negative parity state at Ex = 2.71(2) MeV by the beta-delayed neutron measurement of 17B (H. Ueno et al., Phys. Rev. C 87, 034316 (2013)). Raimann et al. have suggested an unbound state at Ex = 1.18(1) MeV with indefinite spin-parity from the beta-decay study (G. Raimann et al., Phys. Rev. C 53, 453 (1996)). To clarify the situation and further to add spectroscopic information, the measurement was performed for the 12C(18C,17C*) one-neutron knockout reaction channel at 250 MeV/nucleon using the SAMURAI spectrometer at RIKEN-RIBF, during the first physics runs of the apparatus. The nucleon knockout reaction utilizing the secondary beams in inverse kinematics has become recognized as a powerful tool for spectroscopy of the nuclei far from beta-stability. In the presentation we will discuss the details of the measurement and analysis, by focusing on an attempt to extract the orbital angular momenta of the low-lying states in 17C from the parallel momentum distributions of the knockout residues.

How to extract an electric dipole (E1) breakup cross section \sigma (E1) from one-neutron removal cross sections measured at 250MeV/nucleon by using 12C and 208Pb targets, \sigma_{-1n}^{C} and \sigma_{-1n}^{Pb}, respectively, is discussed. It is shown that within about 5% error, \sigma (E1) can be obtained by subtracting \Gamma \sigma_{-1n}^{C} from \sigma_{-1n}^{Pb}, as assumed in preceding studies. However, for the reaction of weakly-bound projectiles, the scaling factor \Gamma is found to be about two times as large as that usually adopted. As a result, we obtain 13--20% smaller \sigma (E1) of ^{31}Ne at 250MeV/nucleon than extracted in a previous analysis of experimental data. By compiling the values of \Gamma obtained for several projectiles, \Gamma=(2.30+/-0.41)\exp(-S_n)+(2.43+/-0.21) is obtained, where S_n is the neutron separation energy. The target mass number dependence of the nuclear parts of the one-neutron removal cross section and the elastic breakup cross section is also investigated.

Most theoretical calculations of direct reactions involving halo nuclei rely on a model of inert core + valence nucleons. However, the internal degrees of freedom of the core may play an important role in the reactions. For inelastic and transfer reactions this has been demonstrated recently in [1] using the framework of exact Faddeev-type equations. This study is being extended to breakup reactions in the intermediate-energy regime where recent measurements at GSI were performed. In addition to core excitation already included in [1] also the knockout of the nucleons from the core is studied. First results will be presented. [1] A. Deltuva, Phys. Rev. C 88, 011601(R) (2013).

Deuteron-induced reactions are being used to produce medical radioisotopes [1] and as surrogates to other reactions (see review [2] and references therein), among their recent applications. Although they have been studied for decades [3-6], the complexity of these reactions continues to make their theoretical description challenging. The direct reaction mechanism is a major contributor to the reaction cross section due to the low binding energy of the deuteron. Competition between elastic breakup, absorption of only a neutron or a proton (stripping and inelastic breakup) and absorption of the deuteron must be taken into account to determine the formation or not of a compound nucleus and its subsequent decay. The inelastic breakup reactions – those in which either only a neutron or a proton is absorbed – are particularly complex, as they form compound nuclei with a wide range of excitation energies and angular momenta. We present the results of a theoretical study of elastic and inelastic deuteron breakup for a large selection of targets at incident deuteron energies below 100 MeV. We use the zero-range post-form DWBA approximation to calculate the elastic breakup cross section [3,4] and its extension to absorption channels to calculate the inelastic breakup cross sections [5,6]. We discuss the regularities and ambiguities in our results, as well as the irregularities in the inelastic breakup energy and angular momentum distributions that complicate their substitution by a smooth distribution obtained from systematics. References [1] E.Betak et al, Technical Reports Series 473, "Nuclear Data for the Production of Therapeutic Radionuclides", IAEA, Vienna, Austria, 2011, ISBN 978-92-0-115010-3. [2] J.E. Escher, J.T. Burke, F.S. Dietrich, N.D. Scielzo, I.J. Thompson, and W.Younes, Rev. Mod. Phys. 84, 353 (2012). [3] G. Baur and D. Trautmann, Phys. Rep. 25, 293 (1976). [4] G. Baur, F. Rösel, D. Trautmann and R. Shyam, Phys. Rep. 111, 333 (1984). [5] A. Kasano and M. Ichimura, Phys. Lett. B115, 81 (1982). [6] N. Austern, Y. Iseri, M. Kamimura, M. Kawai, G. Rawitscher and M. Yahiro, Phys. Rep. 154, 125 (1987).

The structure of nuclei in the Z ~ 40, N ~ 60 mass region is perhaps best characterized by the sudden onset of deformation seen in the transition from N=58-60 [1]. This sudden onset of deformation can lead to both spherical and deformed gaps near the Fermi energy level for the same combination of nucleon numbers. The distance of the gaps allows a nucleus to have a coexistence of shapes, as has been observed in 96Sr. Work to better understand the competition and stabilization of different shapes in these nuclei is of substantial interest both experimentally and theoretically. To help drive the ongoing theoretical discussion of both mean field [2,3] and shell model [4] calculations, measurements of the occupations of shape-driving orbitals in this mass region is critical. The present experiment probes this shape transition region by using a one-neutron transfer reaction with a high mass radioactive beam in inverse kinematics. The d(94Sr,p)95Sr reaction was performed using the TIGRESS gamma-ray spectrometer [5] in conjunction with the SHARC charge particle detector [6]. The ${}^{94}$Sr beam was produced by impinging a 500 MeV proton beam on an ISAC UCx target; the extracted beam was than charge breed using an ECR to 15+ before being accelerated to 5.47 MeV/u and delivered to the experimental station. This is the first high mass (A>30) accelerated radioactive beam experiment at the TRIUMF ISAC-II facility. The combination of detected gamma-rays as-well-as light charge-particles are being used to extract energy levels, cross-sections, and proton angular distributions of low-lying states. Analysis of Doppler-corrected gamma-ray transitions show evidence for direct population of at least four excited states populated in 95Sr. Results will be presented and discussed in the context of the evolution of single-particle structure and compared to modern shell model calculations. [1] K. Heyde and J.~L. Wood, Rev. Mod. Phys.{\bf{83}}, 1467, (2011). [2] R.~Rodriguez-Guzman, $etal.$, Phys. Lett. B {\bf{691}}, 202 (2010). [3] H.~Mei $etal.$, Phys. Rev. C {\bf{85}}, 034321 (2012). [4] K.~Sieja $etal.$, Phys. Rev. C {\bf{79}}, 064310 (2009). [5] G.~Hackman and C. E. Svensson, Hyper. Int. {\bf{225}}, 241 (2014). [6] C.~A.~Diget $etal$ 2011 J. Inst., $\mathbf{6}$, P02005, (2011).

The recent improvements in the experimental sensitivity have opened new avenues to study very neutron-rich isotopes of Carbon and Oxygen, allowing for an improved understanding of the structure of them. The present work aims at exploration of neutron- unbound states of 19C via a one neutron knockout reaction. A study of 19C utilizing in-beam γ-ray spectroscopy measurement reported that the 3/2+1 and 5/2+1 states are bound. On the other hand, in a study of inclusive one-neutron knockout cross section, argued that the experimental inclusive knockout cross section from 20C to 19C did not support the existence of the 5/2+1 state below the threshold. In this work, the invariant mass measurement in inverse kinematics was carried out in order to clarify the issue of bound/unbound nature of the 5/2+1 state. The experi- ment was performed at the RIBF facility in RIKEN. A 20C secondary beam produced by BigRIPS with an energy of 280 MeV/nucleon impinged on a carbon target placed before the SAMURAI spectrometer. By taking full advantage of the analyzer system comprised of a large-acceptance super-conducting dipole magnet, associated tracking de- tectors, and a large volume neutron detector system, an invariant mass spectrum for the system of 18C+n was reconstructed. Details of the measurement and analysis along with new results on the low-lying states of 19C will be presented.

Elastic angular distributions of the 6He+120Sn and 6He+58Ni scatterings have been measured at energies slightly above the Coulomb barrier. Three and four-body continuum discretized coupled channels calculations have been performed. For the 6He+58Ni system, the three-body CDCC calculation underestimates the experimental cross sections in the intermediate angles region and the four-body calculation reproduces very well the data in the whole angular range of the measurements. In these CDCC calculations we folded realistic optical potentials of the n+target and alpha+target sub-systems, to bild the total 6He+target potential. No parameter adjustment has been performed and the results can be considered as predictions. Total reaction cross-sections have been obtained from the CDCC results and are compared with the cross sections for several stable systems. The total reaction cross section of the exotic system 6He+target are systematically larger than the weakly bound stable systems, such as 6Li+target. A large yield of alpha particles has been observed in the spectra of the 6He+120Sn collision, with velocities around the velocity of the projectile and, this alpha particle yield seems to account for the observed enhancement in the total reaction cross section.

Spin asymmetry in direct reactions is rich source of information on nuclear structure, reaction mechanism, and spin-dependent interactions. From more than half century ago, a number of scattering experiments using polarized light ions have been performed at facilities all over the world. Application of such powerful methods to the field of unstable nuclei should enable us to reveal new aspects of atomic nuclei. With such a motivation, we have constructed a solid polarized proton target for radioactive-ion beam experiments under inverse kinematics [1]. The target can be operated in a low magnetic field of 0.1 T, which allows detection of recoil protons with good angular and energy resolutions. The target has been applied to several RI-beam experiments at intermediate energies of several tens to a few hundred MeV/nucleon [2]. One of the future directions of such polarization study is to apply the target to low- energy beam experiments at several to a few tens of MeV/nucleon. Combination of low-energy RI-beam and polarized proton target will open up new possibilities of the spin-asymmetry measurement for low-energy reactions such as resonant scattering and transfer reaction. We could also polarize the RIs embedded in the target, or polarize slow neutrons by using the difference between spin parallel and antiparallel p–n cross sections. Among them, a special focus will be put on the possibility of the resonant proton scattering, which is a powerful spectroscopic tool for extracting single-particle information of exotic nuclei. Spin asymmetry in resonant scattering will be useful in determining the spin-parity of the resonance states without model dependence. The spin asymmetry will also be effective in identifying broad resonances which overlap with each other. This would be particularly important in the spectroscopy of nuclei near/beyond the dripline, where the resonance width is extremely large [3]. In this presentation, we will discuss the physics opportunities expected in the low- energy beam experiment with polarized protons. We will also introduce an experimental plan of 9C+¥vec{p} resonant scattering to probe 10N levels (mirror nucleus of 10Li), which provide important information on n-9Li potential for constructing the three-body model of 11Li (9Li+n+n). [1] T. Wakui, Proceedings of XIth Int. Workshop on Polarized Ion Sources and Polarized Gas Targets 2005, World Scientific, Singapore (2007). [2] T. Uesaka, S. Sakaguchi et al., Phys. Rev. C 82, 021602(R) (2010); S. Sakaguchi et al., Phys. Rev. C 84, 024604 (2011); S. Sakaguchi et al., Phys. Rev. C 87, 021601(R) (2013). [3] T. Teranishi et al., AIP Conf. Proc. 1525, 552 (2013).

Evolution of collectivity in the vicinity of N=Z has attracted a lot of attention due to the large variety of nuclear shapes manifested in the ground and excited states. Above the doubly magic nucleus 56Ni, collectivity in the 2+->0+ transition gradually increases up to 72Kr along N=Z, which is followed by the rapid enhancement of collectivity toward 76Sr[1] and 80Zn with a significant intrusion of the deformation driving g9/2 orbital[2]. Recent lifetime measurement at NSCL quantified B(E2) for the first 2+ state in 76Sr and confirms the large collectivity corresponding to beta=0.45[1]. Additional interest focuses on the pronounced shape coexistence in the A~70 and N~Z region, where prolate and oblate configurations can coexist in a single nucleus or even mix in a single eigenstate. Here we present recent lifetime measurements[3] of the 2+ and 4+ states in the self-conjugate nucleus 72Kr at N=Z. The occurrence of the oblate ground state in 72Kr[4] has provided unique opportunities to investigate the oblate-prolate shape phase transition along the Kr isotopic chain. In this work, we examined a possible rapid shape transition among the yrast states in 72Kr at low spin. The experiment was performed at NSCL using a combination of state-of-the-art instruments including the next-generation gamma-ray tracking array GRETINA[5]. A novel application of the recoil-distance method based on the use of multi-layer foils was demonstrated by taking advantage of excellent position and energy resolution of GRETINA. The present approach significantly extends the sensitive range of lifetimes that can be covered with a single setup and thus enables us to study several states simultaneously. In this talk, we will present the excellent performance of GRETINA in the lifetime measurement and discuss our new results in comparison with a variety of theoretical calculations, which points to the possible rapid shape evolution in the yrast states of 72Kr. Perspectives for direct reaction studies on 72Kr will also be discussed. REFERENCES [1] A.Lemsson et al., Phys. Rev. C 85, 041303(R) (2012). [2] K.Langanke et al., Nucl. Phys. A 728, 109 (2003). [3] H.Iwasaki et al., accepted in Phys. Rev. Lett. [4] E.Bouchez et al., Phys. Rev. Lett. 90, 082502 (2003). [5] S.Paschalis et al., Nucl. Instrum. Meth. A 709, 44 (2013).

Removal reactions have played a key role in investigating properties of valence nucleons in weakly-bound nuclei such as one- and two-neutron halo nuclei. Spectroscopic factors and orbital angular momenta of valence nucleons in incident nuclei can be deduced from the removal cross sections. To understand such properties of halo nuclei, an accurate analysis for neutron removal reactions is highly desired. The eikonal reaction theory (ERT) proposed lately is a method of calculating one- and two-neutron removal reactions at intermediate incident energies in which Coulomb breakup is treated accurately with the continuum discretized coupled-channels method (CDCC). In the presentation, we analyze neutron removal reactions for 6He scattering on 12C and 208Pb at 240 MeV/nucleon and also 28Si at 56 MeV/nucleon. The ERT results are successful in reproducing experimental data. In particular, the ERT results for the heavy target in which Coulomb breakup is important yield much better agreement with the experimental data than the Glauber model results. Furthermore, we will discuss neutron removal cross sections for Be- and C-isotopes.