One-neutron knockout from Sc51-55 Schwertel, S.; Maierbeck, P.; Krucken, R. ...
The European physical journal. A, Hadrons and nuclei,
12/2012, Letnik:
48, Številka:
Dec.
Journal Article
Recenzirano
Results are presented from a one-neutron knockout experiment at relativistic energies of approximate to 420 A MeV on Sc51-55 using the GSI Fragment Separator as a two-stage magnetic spectrometer and ...the Miniball array for gamma-ray detection. Inclusive longitudinal momentum distributions and cross-sections were measured enabling the determination of the contributions corresponding to knockout from the nu p(1/2), nu p(3/2), (L = 1) and nu f(7/2), nu f(5/2) (L = 3) neutron orbitals. The observed L = 1 and L = 3 contributions are compared with theoretical cross-sections using eikonal knockout theory and spectroscopic factors from shell model calculations using the GXPF1A interaction. The measured inclusive knockout cross-sections generally follow the trends expected theoretically and given by the spectroscopic strength predicted from the shell model calculations. However, the deduced L = 1 cross-sections are generally 30-40% higher while the L = 3 contributions are about a factor of two smaller than predicted. This points to a promotion of neutrons from the nu f(7/2) to the nu p(3/2) orbital indicating a weakening of the N = 28 shell gap in these nuclei. While this is not predicted for the phenomenological GXPF1A interaction such a weakening is predicted by recent calculations using realistic low-momentum interactions V-lowk obtained by evolving a chiral N3LO nucleon-nucleon potential.
EXL (EXotic nuclei studied in Light-ion induced reactions at the NESR storage ring) is a project within NUSTAR at FAIR. It aims at investigations of light-ion induced direct reactions in inverse ...kinematics with radioactive ions cooled and stored in the future NESR (New Experimental Storage Ring). The existing ESR (Experimental Storage Ring) at GSI, together with its internal gas-jet target, provides a unique opportunity to perform such kind of experiments on a smaller scale at the present time. We have developed a UHV-compatible (Ultra High Vacuum) detector setup mainly based on DSSDs (Double-sided Silicon-Strip Detector) for the target-like recoils 4. 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 super(56)Ni(p,p) super(56)Ni in inverse kinematics in order to measure the differential cross section for elastic proton scattering and deduce the nuclear-matter distribution and radius of super(56)Ni. In the following, the experimental setup is introduced in more detail, and the current status of the ongoing analysis is discussed.
One-neutron knockout reactions in a 9 Be target have been investigated at relativistic energies, near 700 MeV/u, for a set of sd-shell, neutron-rich nuclei. The experiment was performed in the FRS ...spectrometer, at GSI. gamma-ray measurements were carried out by means of the MINIBALL gamma-ray spectrometer and allowed the determination of partial cross-sections and branching ratios corresponding to the final states of the emerging knockout fragments. Experimental results are presented for C-17, N-19, O-21 and F-25 projectiles. The role of excited states of the N - 1 fragments in the composition of the ground state of these neutron-rich projectiles is outlined in this work.
Production cross-sections for some exotic fragments produced in the reaction {sup 40}Ar+Be at 1000 MeV/nucleon have been studied. These data, together with new available data at higher projectile Z, ...and with new data for the same reaction at lower energies, allowed a revision of the semi-empirical EPAX formula. A discussion of some of the improvements introduced in this semi-empirical parameterization will be presented in this contribution.
Excitation spectra of ^{11}C are measured in the ^{12}C(p,d) reaction near the η^{'} emission threshold. A proton beam extracted from the synchrotron SIS-18 at GSI with an incident energy of 2.5 GeV ...impinges on a carbon target. The momenta of deuterons emitted at 0° are precisely measured with the fragment separator (FRS) operated as a spectrometer. In contrast to theoretical predictions on the possible existence of deeply bound η^{'}-mesic states in carbon nuclei, no distinct structures are observed associated with the formation of bound states. The spectra are analyzed to set stringent constraints on the formation cross section and on the hitherto barely known η^{'}-nucleus interaction.
Proton radii of ^{12-19}C densities derived from first accurate charge changing cross section measurements at 900A MeV with a carbon target are reported. A thick neutron surface evolves from ∼0.5 ...fm in ^{15}C to ∼1 fm in ^{19}C. The halo radius in ^{19}C is found to be 6.4±0.7 fm as large as ^{11}Li. Ab initio calculations based on chiral nucleon-nucleon and three-nucleon forces reproduce the radii well.
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