Study of the 6He+9Be elastic scattering at low energeies
K. C. C. Pires 1*, R. Lichtenthäler 1, A. Moro 2, M. Rodríguez-Gallardo 2,3, A. Lé́pine-Szily 1, V. Guimarães 1, P. N. de Faria 1, D. R. Mendes Junior 1, A. Barioni 1, M. C. Morais 1, V. Morcelle 1, R. Pampa Condori 1, E. Crema 1, M. Assunção 4, J. M. B. Shorto 5, S. Mukherjee 6
1 Departamento de Física Nuclear, Universidade de São Paulo, C.P. 66318, 05389-970, São Paulo, Brazil.
2 Departamento de FAMN, Facultad de Física, Universidad de Sevilla, Apdo. 1065, E-41080 Sevilla, Spain.
3 Instituto de Estructura de la Materia, CSIC, Serrano 123, E-28006 Madrid, Spain.
4 Departamento de Ciências Exatas e da Terra, Universidade Federal de São Paulo, Campus Diadema, São Paulo, Brazil.
5 Instituto de Pesquisas Energéticas e Nucleares (IPEN-CNEN), Comissão Nacional de Energia Nuclear, São Paulo, Brazil.
6 Physics Department, Faculty of Science, The M.S. University of Baroda, Vadodara, India.
New data of the 6He+9Be elastic scattering at Elab=16.2 MeV and 21.3 MeV have been measured. A very large reaction cross section has been previously observed in the collision of 6He with medium and heavy mass targets , which has been attributed to high 6He breakup probability in the strong Coulomb+nuclear interaction. More recently the importance of neutron transfer reactions between projectile and target has been pointed out [2,3]. The main goal of the present experiment is to investigate the halo nature of the 6He nucleus by its interaction with a light target.
The experiment has been performed at the Pelletron Laboratory of the Institute of Physics of the University of Sao Paulo, Brazil, using the RIBRAS facility . The RIBRAS system consists of two superconducting solenoids used to focus and select the radioactive secondary beam. The 6He secondary beam was produced by the 9Be(7Li,6He) reaction with a 7Li primary beam of 200nA. The detection system consisted of four ∆E-E Silicon telescopes, with 20μm and 1000μm thickness respectively, which allow to separate the 6He particles from the 7Li, 4He, and light particles contaminants.
The 6He+9Be angular distributions have been analyzed with optical model, Coupled Channels (CC) and Continuum Discretized Coupled Channels (CDCC) calculations. The comparison between the experimental data and the CDCC calculations allow us to conclude that the breakup of the projectile via the coupling to the 6He 2+ resonance is very important to reproduce the data. In addition, we studied the effect of excitation of the 9Be target explicitly by a CC calculation, using a collective model to describe the excitation of the first low lying states of 9Be. We found that the coupling to these states significantly affects the elastic scattering. From this analysis it was possible to obtain the total reaction cross section which was compared with other stable light systems. All the calculations were carried out with the computer code FRESCO .
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