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We investigate 6He scattering on 27Al, 58Ni, 120Sn, and 208Pb in a microscopic version of the Continuum Discretized Coupled Channel (CDCC) method. We essentially focus on energies around the Coulomb barrier. The 6He nucleus is described by an antisymmetric 6-nucleon wave function, defined in the Resonating Group Method. The 6He continuum is simulated by square-integrable positive-energy states. The model does not depend on any adjustable parameter as it is based only on well known nucleon-target potentials. We show that experimental elastic cross sections are fairly well reproduced. The calculation suggests that breakup effects increase for high target masses. For a light system such as 6He+27Al, breakup effects are small, and a single-channel approximation provides fair results. [ABSTRACT FROM AUTHOR]

The 2H(d,p)3H, 2H(d,n)3He, and 2H(d,γ)4He reactions at low energies are studied with realistic nucleon-nucleon interactions in an ab initio approach. The obtained astrophysical S-factors are all in very good agreement with experiment. The most important channels for both transfer and radiative capture are all found to dominate thanks to the tensor force. [ABSTRACT FROM AUTHOR]

The Continuum Discretized Coupled Channel (CDCC) method is extended to a fully microscopic treatment of the projectile, which is described by the Resonating Group Method. We present a first application to 7Li+208Pb elastic and inelastic scattering around the Coulomb barrier. Experimental cross sections are well reproduced by the model. [ABSTRACT FROM AUTHOR]

The RIBRAS facility (Radiactive Ion Beams in Brasil) is installed next to the 8 MV Pelletron Tandem of the Nuclear Physics Laboratory of the Institute of Physics of the University of São Paulo. It consists of two superconducting solenoids with maximum magnetic field of B=6.5T. Light radioactive ion beams are produced through transfer reactions, using solid or gaseous production targets of Be, LiF, 3He etc. The solenoids make a magnetic rigidity selection and the use of the two solenoids with a degrader between them allows the production of quite pure secondary beams. Beams of 6He, 8Li, 7Be, 10Be, 8B, 12B are currently produced and used to study elastic, inelastic, and transfer reactions on a variety of light, medium mass and heavy secondary targets. Some examples of reactions recently studied are presented below. [ABSTRACT FROM AUTHOR]

We present the results of the 8Li(p, α) 5He reaction of astrophysical interest, measured at the RIBRAS system. It was realized in inverse kinematics and using a thick CH2 polyethylene target. Using the thick target method the complete excitation function could be measured between Ecm = 0.2-2.5 MeV, which includes the Gamow peak energy region. The contribution of contaminating 12C(8Li,4He) 16N and 12C(7Li, 4He) 15N reactions is still under analysis. However, if the cross section is expected to be somewhat reduced, the subtraction of the contamination will not change the general feature of the excitation function. [ABSTRACT FROM AUTHOR]

We present the results of the 8Li(p,α)5He transfer reaction, measured at the RIBRAS facility. It was performed in inverse kinematics using a thick CH2 polyethylene target. The complete excitation function was measured between Ecm = 0.4-2.7 MeV, which includes the Gamow peak energy region. The excitation function was reproduced with the R-matrix theory. [ABSTRACT FROM AUTHOR]

The E2 component of the 12C(α, γ)16O cross section is investigated by a microscopic cluster model, and by R-matrix fits. The first approach provides SE2(300 keV)≈50 keV-b for ground-state transitions. In the R-matrix theory, we show that the background term plays a crucial role, and cannot be determined without ambiguity. Only an upper limit on the extrapolated S factor can be obtained [SE2(300 keV)<190 keV-b]. To constrain the R-matrix analysis, we use the GCM Asymptotic Normalization Constant (ANC) of the 21+ level. This procedure strongly reduces the uncertainties on the R-matrix fit, and we end up with a recommended value of SE2(300 keV) =42±2 keV-b. As ANC values derived from indirect methods are not consistent with the 12C(α, γ)16O cascade transitions to the 21+ state, we suggest a remeasurement of this cross section. [ABSTRACT FROM AUTHOR]

The effect of variations of the fundamental constants on the thermonuclear rate of the triple alpha reaction, 4He(αα, γ)12C, that bridges the gap between 4He and 12C is investigated. We have followed the evolution of 15 and 60 M⊙ zero metallicity stellar models, up to the end of core helium burning. They are assumed to be representative of the first (Population III) stars. The calculated oxygen carbon abundances resulting from helium burning can then be used to constrain the variation of the fundamental constants. [ABSTRACT FROM AUTHOR]

Elastic scattering of light weakly bound nuclei is studied within the Feshbach generalized optical model. The model explicitly takes into account the contribution of the projectile break-up continuum treated within a microscopic few-cluster model. The model is tested on deuteron and 6Li elastic scattering by different targets at intermediate energies. The generalized optical potentials are then calculated for 6He (230 MeV)+12C reaction treating the projectile nucleus either within two-body (α+2n) or three-body (α+n+n) approximations. The obtained differences are analyzed. [ABSTRACT FROM AUTHOR]

This work is devoted to new investigations of the 12Be spectrum with No-core Shell Model (NCSM) calculations and with the Generator Coordinate Method (GCM). The NCSM calculations do not reproduce the breaking of the N = 8 shell closure. The NCSM and the GCM calculations do not support the existence of a band based on the ground state. The GCM calculations lead to a good description of the molecular band of Freer et al. and Saito et al.. The 02+ isomeric state and the 22+ state are also well described by the GCM. New bands of positive and negative parities are proposed. [ABSTRACT FROM AUTHOR]

The reaction 13C(α,n)16O is considered as the main neutron source for s-process in low-mass asymptotic giant branch stars. At low energies of astrophysical interest, the contribution of the subthreshold state 6.356 MeV of 17O to the 13C(α,n)16O cross section should be taken into account. However, the results of previous studies of this contribution lead to different conclusions. Hence, we investigated the effect of this resonance on the astrophysical S-factor through a new precise measurement of the alpha spectroscopic factor, Sα, of the 6.356 MeV state using the transfer reaction 13C(7Li,t)17O at two different incident energies. The measured angular distributions and the obtained spectroscopic factors will be presented as well as their impact on C(α,n)16O cross section and reaction rate. [ABSTRACT FROM AUTHOR]

The low-energy levels of 19Na were studied in the center-of-mass energy (ECM) range from 2.6 to 3.4 MeV, by using the elastic and inelastic scattering methods in inverse kinematics. The 18Ne+p scattering reactions, leading to the ground state and the first excited state of 18Ne, were investigated by using a 66 MeV radioactive 18Ne beam and a polyethylene (CH2)n target. The experimental methods and the set-up are described and preliminary results are presented. [ABSTRACT FROM AUTHOR]

The 14O+p elastic scattering is analyzed in a fully microscopic cluster model. With the Resonating Group Method associated with the microscopic R-matrix theory, phase shifts and cross sections are calculated. Data on 16O+p are used to test the precision of the model. For the 14O+p elastic scattering, an excellent agreement is found with recent experimental data. Resonances properties in 15F are discussed. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

We have investigated the low-energy states of 11N by the elastic scattering method in inverse kinematics using a 10C beam and a (CD2)n target. Recoil protons were detected at 16 laboratory angles θlab = 4.6° – 18.9° in a ΔE - E detector system. Using the R-matrix method to analyse the 10C + p elastic cross sections, we found 11N to be unbound with respect to proton emission by 1.54±0.02 MeV with a decay width of 0.83±0.03. These results are used to calculate the two-proton decay width of the 12O ground state. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Low-lying states of 19Na were investigated using both elastic and inelastic scattering of a 18Ne beam on a (CH2)n target. The experimental method is briefly described. Preliminary results are presented. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

An exclusive study of 17F breakup reactions has been performed at the FRIBs facility of the Laboratori Nazionali del Sud in Catania (Italy). The experiment has been performed with the aim of testing the accuracy of the Coulomb-breakup indirect technique used to infer radiative-capture cross sections at low energies. This technique has been used in the 7Be(p,γ)8B case, but has never been tested. By measuring the breakup of 17F into 16O+p, and comparing the inferred cross section for 16O(p,γ)17F to direct precise measurements, the influence of E2 transitions and higher-order effects, that are predicted to be significant in Coulomb-breakup reactions, can be evaluated. The first results and preliminary model comparison are reported. [ABSTRACT FROM AUTHOR]