1,136 research outputs found

    The surface diffuseness and the spin-orbital splitting in relativistic continuum Hartree-Bogoliubov theory

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    The Relativistic Continuum Hartree Bogoliubov theory (RCHB), which is the extension of the Relativistic Mean Field and the Bogoliubov transformation in the coordinate representation, has been used to study tin isotopes. The pairing correlation is taken into account by a density-dependent force of zero range. RCHB is used to describe the even-even tin isotopes all the way from the proton drip line to the neutron drip line. The contribution of the continuum which is important for nuclei near the drip-line has been taken into account. The theoretical S2nS_{2n} as well as the neutron, proton, and matter rmsrms radii are presented and compared with the experimental values where they exist. The change of the potential surface with the neutron number has been investigated. The diffuseness of the potentials in tin isotopes is analyzed through the spin-orbital splitting in order to provide new way to understand the halo phenomena in exotic nuclei. The systematic of the isospin and energy dependence of these results are extracted and analyzed.Comment: 11 figure

    Microscopic multicluster description of neutron-halo nuclei with a stochastic variational method

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    To test a multicluster approach for halo nuclei, we give a unified description for the ground states of 6^6He and 8^8He in a model comprising an α\alpha cluster and single-neutron clusters. The intercluster wave function is taken a superposition of terms belonging to different arrangements, each defined by a set of Jacobi coordinates. Each term is then a superposition of products of gaussian functions of the individual Jacobi coordinates with different widths, projected to angular momenta l=0l=0 or 1. To avoid excessively large dimensions and ``overcompleteness", stochastic methods were tested for selecting the gaussians spanning the basis. For 6^6He, we were able to calculate ground-state energies that are virtully exact within the subspace defined by the arrangements and ll values, and we found that preselected random sets of bases (with or without simulated annealing) yield excellent numerical convergence to this ``exact" value with thoroughly truncated bases. For 8^8He good energy convergence was achieved in a state space comprising three arrangements with all l=0l=0, and there are indications showing that the contributions of other subspaces are likely to be small. The 6^6He and 8^8He energies are reproduced by the same effective force very well, and the matter radii obtained are similar to those of other sophisticated calculations.Comment: Latex , 8 figures available on request, ATOMKI-4-1993-

    Exotic nuclei far from the stability line

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    The recent availability of radioactive beams has opened up a new era in nuclear physics. The interactions and structure of exotic nuclei close to the drip lines have been studied extensively world wide, and it has been revealed that unstable nuclei, having weakly bound nucleons, exhibit characteristic features such as a halo structure and a soft dipole excitation. We here review the developments of the physics of unstable nuclei in the past few decades. The topics discussed in this Chapter include the halo and skin structures, the Coulomb breakup, the dineutron correlation, the pair transfer reactions, the two-nucleon radioactivity, the appearance of new magic numbers, and the pygmy dipole resonances.Comment: 43 pages, 30 eps figures. chapter in "100 years of subatomic physics", edited by E.M. Henley and S. Elli

    The proton and neutron distribution in Na isotopes: the development of halo and shell structure

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    The interaction cross sections for ANa+12C^A Na + ^{12}C reaction are calculated using Glauber model. The continuum Hartree-Bogoliubov theory has been generalized to treat the odd particle system and take the continuum into account. The theory reproduces the experimental result quite well. The matter distributions from the proton drip line to the neutron drip line in Na isotopes have been systematically studied and presented. The relation between the shell effects and the halos has been examined. The tail of the matter distribution shows a strong dependence on the shell structure. The neutron N=28 closure shell fails to appear due to the coming down of the 2p3/22p_{3/2} and 2p1/22p_{1/2}. The development of the halo was understood as changes in the occupation in the next shell or the sub-shell close to the continuum limit. The central proton density is found to be decreasing near the neutron drip line, which is due to the proton-neutron interaction. However the diffuseness of the proton density does not change for the whole Na isotopes.Comment: 10 pages, 4 figure

    Conceptual Design Report for the Scientific Program of the Super-FRS Experiment Collaboration

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    This Conceptual Design Report (CDR) presents the plans of the Super-FRS Experiment Collaboration for a variety of experiments, which build on the versatile high-resolution separator and spectrometer performance of the Super-FRS. The characteristic feature of these experiments is the fact that they use the separator as an integral part of the measurement. These experiments build on the experience of the collaboration and their scientific program pursued at the FRS in the last 25 years, but also includes recently developed novel topics.Under these premises, the Super-FRS Experiment Collaboration has identified ten major topics of current interest and with far-reaching scientific potential. In this CDR, the scientific case is briefly recapitulated and the conceptual design of the experiments, the setups and their implementation are described. Much of the needed equipment is already available or, if not, will be realized with new, additional resources and efforts outside the FAIR Cost Books. The related R&D works and some pilot experiments can be carried out at the existing FRS of GSI in FAIR Phase-0. On the midterm, the science program of this collaboration can start at the commissioning phase of the Super-FRS and will continue on the long term with the established full performance. Accordingly, the prototype equipment and other already existing devices can be tested and used at the FRS and can later, when completed or upgraded, be moved to the Super-FRS, see Appendix I. The related developments and organization of the Super-FRS Experiment Collaboration are described in Appendices II and III, respectively; the collaboration partners and institutes are listed in Appendix IV. The Super-FRS Experiment Collaboration is formally and firmly established and is a comprising part of the NUSTAR Collaboration. A large variety of modern nuclear physics experiments with new scientific possibilities and outstanding scientific potential were presented in the scientific program (GSI-Report 2014-4), which was very positively evaluated and approved by the FAIR-ECE in its 4th meeting in June 2014. In its report, the ECE encouraged the collaboration to develop TDRs. The present CDR is the next step on the way to TDRs for the ancillary equipment, that shall be integrated in the Super-FRS

    Coulomb versus nuclear break-up of 11Be halo nucleus in a non perturbative framework

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    The 11Be break-up is calculated using a non perturbative time-dependent quantum calculation. The evolution of the neutron halo wave function shows an emission of neutron at large angles for grazing impact parameters and at forward angles for large impact parameters. The neutron angular distribution is deduced for the different targets and compared to experimental data. We emphasize the diversity of diffraction mechanisms, in particular we discuss the interplay of the nuclear effects such as the towing mode and the Coulomb break-up. A good agreement is found with experimental data.Comment: 9 figures, this paper was accepter in Nuclear Physics A on sept, 200

    IKEDA, the partner for exploring the nuclear highland far from the valley of stability

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    I have been collaborating with Ikeda since 1980’s when I started the experiment with radioactive nuclear beams. He has been interested in explaining the halo structure and binding energy of 11Li from the very beginning. From these studies, new basic concepts have been introduced, one of such important ideas is the soft resonance and cluster structure of halo nuclei. He also introduced the importance of the tensor forces on the halo formation, in particular for the correlation of two halo neutrons though s- and p- wave mixing. As an experimentalist, I have been trying to provide data to help him to develop these ideas. Here, I present the recent progresses in experimental studies. One is the first measurement of the two-neutron transfer reaction of 11Li to study the correlation between two halo neutrons. The other is a new on going experiment to obtain the direct evidence of the tensor forces in nuclei

    Signatures of synchrotron emission and of electron acceleration in the X-ray spectra of Mrk 421

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    BL Lac objects undergo strong flux variations involving considerable changes in their spectral shapes. We specifically investigate the X-ray spectral evolution of Mrk 421 over a time span of about nine years. We aim at statistically describing and physically understanding the large spectral changes in X rays observed in Mrk 421 over this time span. We perform a homogeneous spectral analysis of a wide data set including archived observations with ASCA, BeppoSax, RXTE, as well as published and unpublished XMM-Newton data. The presence of uncertainties is taken into account in our correlation analysis. The significance of the correlations found and possible spurious effects are studied with Monte Carlo simulations. We find that the Mrk421 spectral energy distribution (SED) has a lower peak at energies that vary in the range, 0.1-10 keV while its X-ray spectrum is definitely curved. Parameterizing the X-ray spectra with a log-parabolic model, we find a positive correlation between the position and the height of the SED peak. In addition, we find a negative trend of the spectral curvature parameter vs. the SED peak energy. We show that these relations between the spectral parameters are consistent with statistical or stochastic acceleration of the emitting particles, and provide insight into the physical processes occurring in BL Lac nuclei.Comment: 11 pages, 5 fiures, Accepted for publication in A&

    Structure Functions of Unstable Lithium Isotopes

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    We study both the spin-average and spin-dependent structure functions of the lithium isotopes, 6−11^{6-11}Li, which could be measured at RIKEN and other nuclear facilities in the future. It is found that the light-cone momentum distribution of the valence neutron in the halo of 11^{11}Li is very sharp and symmetric around y = 1, because of the weak binding. The EMC ratios for Li isotopes are then calculated. We study the possibility of extracting the neutron structure function from data for the nuclear structure functions of the Li isotopes. Next we calculate the spin-dependent structure functions of 7,9,11^{7,9,11}Li isotopes, which have spin of 3/2. The effect of the nuclear binding and Fermi motion on the multipole spin structure function,  13/2g1^{3/2}_{~1}g_1, is about 10% in the region x < 0.7, but it becomes quite important at large x. The spin structure function of  33/2g1^{3/2}_{~3}g_1 is also investigated. Finally, we discuss the modification of the Gottfried and Bjorken integrals in a nuclear medium and point out several candidates for a pair of mirror nuclei to study the flavor-nonsinglet quark distributions in nuclei.Comment: 23 pages + 7 tables + 15 figure

    Toward precision mass measurements of neutron-rich nuclei relevant to rr-process nucleosynthesis

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    The open question of where, when, and how the heavy elements beyond iron enrich our Universe has triggered a new era in nuclear physics studies.\ Of all the relevant nuclear physics inputs, the mass of very neutron-rich nuclides is a key quantity for revealing the origin of heavy elements beyond iron.\ Although the precise determination of this property is a great challenge, enormous progress has been made in recent decades, and it has contributed significantly to both nuclear structure and astrophysical nucleosynthesis studies.\ In this review, we first survey our present knowledge of the nuclear mass surface, emphasizing the importance of nuclear mass precision in rr-process calculations.\ We then discuss recent progress in various methods of nuclear mass measurement with a few selected examples.\ For each method, we focus on recent breakthroughs and discuss possible ways of improving the weighing of rr-process nuclides.Comment: 10 figures, review articles in Frontiers of Physic
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