EURONS Activity N08

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Abstracts of presentations/discussions (a pdf file is available here) 1. Pierre Descouvement (Brussels): Challenges for threebody scattering problems I plan to describe general issues in 3body scattering for nonresonant processes (where the phase shifts are needed) and for resonant processes (where approximate methods are available). I will briefly tackle nonmicroscopic as well as microscopic cluster theories, and show the difficulties associated with a proper treatment of 3body asymptotics. This will be illustrated by some projects going on at the moment: the 5H and 5He(T=3/2) systems, and the 3alpha process. 2. Jeff Tostevin (Surrey): Observing correlations using reactions Intermediate energy direct reactions, involving removal or excitation of single nucleons or pairs of nucleons, can probe nucleon structure at both the weakly and stronglybound Fermi surfaces of unstable nuclei. The contribution will discuss if aspects of nucleon correlations, structure calculations and/or effective interactions might be observable and clarified using such reaction mechanisms. 3. Markus Stauf (Manchester): Coupled cluster method with a hardcore potential for finite nuclei Comparisons are made between the hardcorepotential formulation of the Bochum group and a new symmetric formulation. The calculations are made for the alpha particle. 4. Sofia Quaglioni (LLNL): Extending the ab initio nocore shell model to the continuum via the resonatinggroup method. One of the greatest challenges for nuclear physics today is the development of a quantitative, microscopic theory of lowenergy reactions on light nuclei. We are building such a theory by augmenting the ab initio nocore shell model to include clustering and resonant and nonresonant continuum. For this purpose, we follow an approach in the spirit of the resonating group method. I will present our recent results on nucleon4He scattering. 5. Winfried Leidemann (Trento): Study of reactions with the Lorentz integral transform (LIT) method The LIT approach allows to carry out ab initio calculations of reactions taking into account correctly the manybody continuum. The large range of applications is discussed for nuclei in the mass range from A=27. 6. Marcella Grasso (Orsay): Evolution of proton states in neutronrich Ca and Ar isotopes We analyze the evolution with increasing isospin asymmetry of the proton singleparticle states 2s1/2 and 1d3/2 in Ca and Ar isotopes. It is shown that this evolution is sensitive to the neutron shell structure, the two states becoming more or less close depending on the neutron orbitals which are filled. In the regions where the states get closer some effective interactions lead to an inversion between them. We study in detail the modification of the two singleparticle energies by using the equivalent potential in the Schrödingerlike SkyrmeHartreeFock equations. The role played by central, kinetic, spinorbit and tensor contributions is discussed. Finally, the occurrence of a bubble structure, due to an inversion between the s1/2 and d3/2 states, is investigated in Ar isotopes.
7. Pierre Capel (Brussels): Analysis of 8B breakup experiments with a Dynamical Eikonal Approximation Using the Dynamical Eikonal Approximation [D. Baye et al. Phys. Rev. Lett. 95, 082502 (2005)], we analyse different 8B breakup experiments that have been used as indirect technique to infer 7Be(p,gamma)8B astrophysical S factor. In particular, we analyse the influence of the projectiletarget interaction on several breakup observables. We observe that nuclear interaction can be neglected if data are selected at sufficiently forward angles. However, the influence of the E2 term of the Coulomb potential never seems to be negligible. The accuracy of the extraction of the astrophysical S factor at stellar energies from breakup experiments therefore seems difficult to evaluate.
8. Ron Johnson (Surrey): Transfer Reactions with Deuterons In the late 1960's I developed, with P J R Soper and J D Harvey, a method of calculating (d,p) and (p,d) cross sections which (i) went well beyond the then current DWBA method and included effects due to excitation of the deuteron breakup continuum in a nonperturbative way; (ii) could be easily implemented by a small modification of a DWBA code; (iii) did not involve the concept of a deuteron optical potential with its associated uncertainties; (iv) involved fewer parameters to be determined independently than is needed for a typical DWBA calculation. The method is usually presented as an adiabatic, high energy theory. I will discuss the theoretical challenges involved in extending the range of application of the method to low energies.
9. Marek Ploszajczak (GANIL): Manybody calculations for weaklybound and unbound states The recent progress in a shell model description of weakly bound and unbound manybody states will be presented. In addition to introducing the Shell Model for open quantum systems, I will concentrate on the discussion of threshold anomalies, spectroscopic factors, radial overlap functions, etc.
10. Antonio Sa Fonseca (Lisboa): Threebody approach to direct nuclear reactions Exact threebody equations are used to study direct nuclear reactions involving light bound systems such as deuterons or halo nuclei, where excitation to the continuum plays a important role in the reaction mechanism. We compare results with the standard theoretical approach based on the continuum discretized coupled channel (CDCC) method. Results show that the standard method fails to describe p11Be breakup into p+n+10Be, while it leads to correct results for the breakup of deuterons on 12C. Application to other reactions is shown. Derivation of DWBA from the exact threebody formalism is addressed.
11. Antonio Moro (Sevilla): Extracting spectroscopic information from transfer reactions involving weakly bound nuclei In this talk, I will address the problem of the extraction of spectroscopic information from the analysis of reactions involving loosely bound nuclei. I will discuss the case of transfer to bound states as well as the case of transfer reactions populating continuum states. The first one will be illustrated with the 10Be(d,p)11Be and 11Be(p,d)10Be reactions, while in the latter I will consider the 9Li(d,p)10Li case. Several approaches will be compared and discussed.
12. Manuela Rodriguez Gallardo (Lisboa): Standard fourbody CDCC calculations The extension of the standard CDCC method to fourbody reactions is presented. The bin procedure is generalized to discretize the continuum of the threebody projectile. The method is applied to reactions induced by the Borromean nucleus 6He.
13. Mahir Hussein (MPI Dresden): AbsorptionFluctuation Theorem for Nuclear Reactions We discuss the connection between absorption, averages and fluctuations in nuclear reactions. The fluctuations in the entrance channel result in the compound nucleus, HauserFeshbach, cross section, the fluctuations in the intermediate channels, result in modifications of multistep reaction cross sections exemplified by the possible excitation of BrinkAxel phonons in, e.g., multiphonon giant resonances. The fluctuations in the final channel result in hybrid cross sections that can be used to describe incomplete fusion reactions. We discuss the latter in detail and comment on the validity of the assumptions used in the development of hybrid reaction theories (Trojan Horse, Surrogate Method). We also discuss the theory of multistep reactions with regards to intermediate state fluctuations and the energy dependence and nonlocality of the intermediate channels optical potentials.
14. Jim
AlKhalili (Surrey): The twopotential approach to oneproton emission
15. Paul Stevenson (Surrey): TimeDependent HartreeFock for structure and reactions The most recent implementations of the TimeDependent HartreeFock (TDHF) allow the simulation of dynamical processes in nuclei using effective interactions of the Skyrme type fitted mostly to ground state properties. We present some results using TDHF for resonances and collisions including arbitrary deformation, and discuss strengths and shortcomings of the approach, and the perspectives for improvement.
16. Hermann Wolter (Munich): The nuclear symmetry energy at low density Information on the lowdensity symmetry energy from analysis of low energy heavy ion reactions.
17. Arnau Rios Huguet (MSU): A timedependent Green's functions approach to nuclear reactions
18. Raquel Crespo (IST, LIsboa): Faddeev multiple scattering calculations for proton elastic and breakup scattering from halo nuclei Full Faddeevtype calculations are performed for 11Be elastic and breakup on proton target at intermediate incident energies. The convergence of the multiple scattering expansion is investigated. For elastic scattering the results are calculated with a Glauber type calculation. For breakup, the results are compared with those of other frameworks like Distorted Wave Impulse Approximation. Both Glauber and DWIA approaches are based on an incomplete and truncated multiple scattering expansion. Preliminary results for the one neutron knockout reaction of p14Be using Faddeev and Glauber are reported.
19. Joaquin Gomez Camacho (Sevilla): Algebraic approach to the scattering with internal degrees of freedom Algebraic methods to describe bound and unbound quantum states will be presented. The onedimensional atommolecule scattering problem will be solved using algebraic methods.
20. Gaute Hagen (Oak Ridge): CoupledCluster Approach to Nuclear Structure The nuclear manybody problem is a challenging undertaking. CoupledCluster theory is a microscopic theory recently revived in the nuclear structure community. It represents an ideal compromise between accuracy on the one hand, and computational cost on the other. Further, it is a size extensive theory, this is an essential property when extending the abinitio program into the medium mass regime of the nuclear chart. Recent developments of CoupledCluster theory with two and threebody Hamiltonians, and its application to medium mass nuclei is discussed. Further, the first abinitio calculations of lifetimes and decay widths of a whole isotopic chain starting from nucleon degrees of freedom and realistic nucleonnucleon forces are presented. It is argued that CoupledCluster theory is an ideal tool in the study of properties of weakly bound and unbound nuclei beyond the lightest, and the role of threenucleon forces in medium mass nuclei.
21. Jimmy Rotureau (Oak Ridge): Density Matrix Renormalization Group Approach for many body open quantum systems We have applied the DMRG method in the context of the Gamow Shell Model (GSM). In this model, which describes the configuration mixing in open quantum manybody system, the completeness relation is resolved in the Berggren ensemble consisting of bound states, resonant states (Gamow states) and complex energy continuum states. The eigenvalue problem is inherently nonhermitian and given by complexsymmetric matrix with complex eigenvalues. Inclusion of resonances and associated continuum states leads to an explosive growth of the size of the multiconfigurational space and the standard diagonalization methods cannot be applied. To deal with this difficulty, we have solved the GSM problem using the DMRG technique in the Jscheme. I will show results we have obtained for the description of weakly bound or unbound states in He isotopes.
22. Haik Simon (GSI): Correlation studies in 3body halo breakup reactions I will present the findings for our new experimental results impinging 8He,11Li,14Be on a liquid hydrogen target with proton recoil detection. The results for a few unbound systems across the neutron dripline, populated with proton knockout reactions will be discussed. If time allows I will also say a few words on the experimental reliability of our two neutron data at very low relative energy  in comparison with recent RIKEN results.
23. Jan Vaagen (Bergen): Lessons from Helsinki There will be a discussion of future plans, proposals and developments subsequent to the September 2007 Joint EURISOLEURONS Helsinki Town meeting and the status of the proposed EU Network (NRA) and Joint Research (JRA) initiatives under the FP7 banner. (updated 20 December) 
Webmaster: J.A. Tostevin, University of Surrey. Queries to j.tostevin@surrey.ac.uk 