616 research outputs found
Proton elastic scattering from tin isotopes at 295 MeV and systematic change of neutron density distributions
Cross sections and analyzing powers for proton elastic scattering from
Sn at 295 MeV have been measured for a momentum
transfer of up to about 3.5 fm to deduce systematic changes of the
neutron density distribution. We tuned the relativistic Love-Franey interaction
to explain the proton elastic scattering of a nucleus whose density
distribution is well known. Then, we applied this interaction to deduce the
neutron density distributions of tin isotopes. The result of our analysis shows
the clear systematic behavior of a gradual increase in the neutron skin
thickness of tin isotopes with mass number.Comment: 24 pages, 12 figures. Accepted for publication in Physical Review
Isotopically-Resolved Neutron Cross Sections as Probe of the Nuclear Optical Potential
Neutron scattering experiments provide direct access to the forces experienced by nucleons in the nuclear environment. Due to the experimental difficulty of cross section measurements with neutrons, isotopically-resolved neutron scattering cross sections are sorely needed as inputs for many nuclear models. This dissertation presents the results from a campaign of isotope-specific neutron total cross section measurements on 16,18O, 58,64Ni, 112,124Sn, and 103Rh from 3-450 MeV and elastic scattering differential cross section measurements on 112,nat,124Sn at 11 and 17 MeV. Equipped with these new data and with computational improvements to the Dispersive Optical Model (DOM), we present DOM treatments of 16,18O, 40,48Ca, 58,64Ni, 112,124Sn, and 208Pb. From these analyses across the nuclear chart, we place additional constraints on the neutron-proton asymmetry-dependence of nuclear properties, extract essential bound-state quantities including spectroscopic factors and neutron skins, and identify experimental data sets most needed for further enhancing our understanding of nuclear structure
Nuclear equation of state from ground and collective excited state properties of nuclei
This contribution reviews the present status on the available constraints to the nuclear equation of state (EoS) around saturation density from nuclear structure calculations on ground and collective excited state properties of atomic nuclei. It concentrates on predictions based on self-consistent mean-field calculations, which can be considered as an approximate realization of an exact energy density functional (EDF). EDFs are derived from effective interactions commonly fitted to nuclear masses, charge radii and, in many cases, also to pseudo-data such as nuclear matter properties. Although in a model dependent way, EDFs constitute nowadays a unique tool to reliably and consistently access bulk ground state and collective excited state properties of atomic nuclei along the nuclear chart as well as the EoS. For comparison, some emphasis is also given to the results obtained with the so called ab initio approaches that aim at describing the nuclear EoS based on interactions fitted to few-body data only. Bridging the existent gap between these two frameworks will be essential since it may allow to improve our understanding on the diverse phenomenology observed in nuclei. Examples on observations from astrophysical objects and processes sensitive to the nuclear EoS are also briefly discussed. As the main conclusion, the isospin dependence of the nuclear EoS around saturation density and, to a lesser extent, the nuclear matter incompressibility remain to be accurately determined. Experimental and theoretical efforts in finding and measuring observables specially sensitive to the EoS properties are of paramount importance, not only for low-energy nuclear physics but also for nuclear astrophysics applications
Electric and magnetic dipole strength in 112,114,116,118,120,124Sn
Inelastic proton scattering experiments were performed at the Research Center
for Nuclear Physics, Osaka, with a 295 MeV beam covering laboratory angles
0{\deg}-6{\deg} and excitation energies 6-22 MeV. Cross sections due to E1 and
M1 excitations were extracted with a multipole decomposition analysis and then
converted to reduced transition probabilities with the "virtual photon method"
for E1 and the "unit cross section method" for M1 excitations, respectively.
Including a theory-aided correction for the high excitation energy region not
covered experimentally, the electric dipole polarizability was determined from
the E1 strength distributions. Total photoabsorption cross sections derived
from the E1 and M1 strength distributions show significant differences compared
to those from previous (,xn) experiments in the energy region of the
isocvector giant dipole resonance (IVGDR). The widths of the IVGDR deduced from
the present data with a Lorentz parameterization show an approximately constant
value of about 4.5 MeV in contrast to the large variations between isotopes
observed in previous work. The IVGDR centroid energies are in good
correspondence to expectations from systematics of their mass dependence.
Furthermore, a study of the dependence of the IVGDR energies on bulk matter
properties is presented. The E1 strengths below neutron threshold show fair
agreement with results from (,') experiments on
112,116,120,124Sn in the energy region between 6 and 7 MeV. At higher
excitation energies large differences are observed pointing to a different
nature of the excited states with small ground state branching ratios. The
isovector spin-M1 strengths exhibit a broad distribution between 6 and 12 MeV
in all studied nuclei.Comment: 32 pages, 23 figures, submitted to Phys. Rev.
Nuclear Astrophysics with Radioactive Beams
The quest to comprehend how nuclear processes influence astrophysical
phenomena is driving experimental and theoretical research programs worldwide.
One of the main goals in nuclear astrophysics is to understand how energy is
generated in stars, how elements are synthesized in stellar events and what the
nature of neutron stars is. New experimental capabilities, the availability of
radioactive beams and increased computational power paired with new
astronomical observations have advanced the present knowledge. This review
summarizes the progress in the field of nuclear astrophysics with a focus on
the role of indirect methods and reactions involving beams of rare isotopes.Comment: 121 pages, 27 figures, 510 references, to appear in Physics Reports.
Minor typos and references fixe
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