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Peripheral elastic and inelastic scattering of 17,18O on light targets at 12 MeV/nucleon

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 Added by Valentin Balanica
 Publication date 2014
  fields
and research's language is English




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A study of interaction of neutron rich oxygen isotopes $^{17,18}$O with light targets has been undertaken in order to determine the optical potentials needed for the transfer reaction $^{13}$C($^{17}$O,$^{18}$O)$^{12}$C. Optical potentials in both incoming and outgoing channels have been determined in a single experiment. This transfer reaction was used to infer the direct capture rate to the $^{17}$F(p,$gamma$)$^{18}$Ne which is essential to estimate the production of $^{18}$F at stellar energies in ONe novae. The success of the asymptotic normalization coefficient (ANC) as indirect method for astrophysics is guaranteed if the reaction mechanism is peripheral and the DWBA cross section calculations are warranted and stable against OMP used. We demonstrate the stability of the ANC method and OMP results using good quality elastic and inelastic scattering data with stable beams before extending the procedures to rare ion beams. The peripherality of our reaction is inferred from a semiclassical decomposition of the total scattering amplitude into barrier and internal barrier components. Comparison between elastic scattering of $^{17}$O, $^{18}$O and $^{16}$O projectiles is made.



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Background: Double charge exchange (DCE) nuclear reactions have recently attracted much interest as tools to provide experimentally driven information about nuclear matrix elements of interest in the context of neutrinoless double-beta decay. In this framework, a good description of the reaction mechanism and a complete knowledge of the initial and final-state interactions are mandatory. Presently, not enough is known about the details of the optical potentials and nuclear response to isospin operators for many of the projectile-target systems proposed for future DCE studies. Among these, the 20Ne + 76Ge DCE reaction is particularly relevant due to its connection with 76Ge double-beta decay. Purpose: We intend to characterize the initial-state interaction for the 20Ne + 76Ge reactions at 306 MeV bombarding energy and determine the optical potential and the role of the couplings between elastic channel and inelastic transitions to the first low-lying excited states. Methods: We determine the experimental elastic and inelastic scattering cross-section angular distributions, compare the theoretical predictions by adopting different models of optical potentials with the experimental data, and evaluate the coupling effect through the comparison of the distorted-wave Born approximation calculations with the coupled channels ones. Results: Optical models fail to describe the elastic angular distribution above the grazing angle (9.4{deg}). A correction in the geometry to effectively account for deformation of the involved nuclear systems improves the agreement up to about 14{deg}. Coupled channels effects are crucial to obtain good agreement at large angles in the elastic scattering cross section.
During therapeutic treatments using ions such as carbon, nuclear interactions between the incident ions and nuclei present in organic tissues may occur, leading to the attenuation of the incident beam intensity and to the production of secondary light charged particles. As the biological dose deposited in the tumor and the surrounding healthy tissues depends on the beam composition, an accurate knowledge of the fragmentation processes is thus essential. In particular, the nuclear interaction models have to be validated using experimental double differential cross sections which are still very scarce. An experiment was realized in 2011 at GANIL to obtain these cross sections for a 95 MeV/nucleon carbon beam on different thin targets for angles raging from 4 to 43{deg} . In order to complete these data, a new experiment was performed on September 2013 at GANIL to measure the fragmentation cross section at zero degree for a 95 MeV/nucleon carbon beam on thin targets. In this work, the experimental setup will be described, the analysis method detailed and the results presented.
The vector analyzing power has been measured for the elastic scattering of neutron-rich 6He from polarized protons at 71 MeV/nucleon making use of a newly constructed solid polarized proton target operated in a low magnetic field and at high temperature. Two approaches based on local one-body potentials were applied to investigate the spin-orbit interaction between a proton and a 6He nucleus. An optical model analysis revealed that the spin-orbit potential for 6He is characterized by a shallow and long-ranged shape compared with the global systematics of stable nuclei. A semimicroscopic analysis with a alpha+n+n cluster folding model suggests that the interaction between a proton and the alpha core is essentially important in describing the p+6He elastic scattering. The data are also compared with fully microscopic analyses using non-local optical potentials based on nucleon-nucleon g-matrices.
Multifragment events resulting from peripheral Au + Au collisions at 35 MeV/nucleon are analysed in terms of critical behavior. The analysis of most of criticality signals proposed so far (conditional moments of charge distributions, Campi scatter plot, fluctuations of the size of the largest fragment, intermittency analysis) is consistent with the occurrence of a critical behavior of the system.
Pion-nucleus elastic scattering at energies above the Delta(1232) resonance is studied using both pi+ and pi- beams on 12C, 40Ca, 90Zr, and 208Pb. The present data provide an opportunity to study the interaction of pions with nuclei at energies where second-order corrections to impulse approximation calculations should be small. The results are compared with other data sets at similar energies, and with four different first-order impulse approximation calculations. Significant disagreement exists between the calculations and the data from this experiment.
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