Determination of astrophysical rates for reaction involving light unstable nuclei relevant to nucleosynthesis in novae and super novae

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Experimental results with fast RI beams provided by the RIKEN accelerator facility have been analyzed, and considerations for future studies were made.1) Proton capture reactions in the rp process studied by the Coulomb dissociation methodBased on the experimental results of the Coulomb dissociation experiments with ^<23>Al and ^<27>P beams, astrophysical reaction rates for explosive hydrogen burning processes have been determined. The critical condition in the temperature and density where the proton capture becomes faster than the positron decay was obtained. In comparison with astrophysical models for novae and X-ray bursts, it turned out that positron decays dominate in novae whereas proton capture is important in X-ray bursts.2) Reaction mechanism study on Coulomb dissociationExperiments of ^8B breakup have been performed with liquid hydrogen and helium targets in addition to a lead target, in order to extract the amount of M1, E2 and nuclear excitation components. Their results a … More re necessary to accurately extract the proton capture cross section from Coulomb dissociation. Extracted elastic scattering angular distributions were analyzed with the optical potential model. Especially, the data for the lead target were well reproduced by the potential used in the previous calculation, confirming the earlier analysis. Through discussions with theorists, existing difference between the results from the direct and Coulomb dissociation experiments may be understood by the effect of multi step processes by microscopic reaction calculations.3) Development of the method to extract M1 transition probabilityIn many reactions involved in explosive hydrogen burning, transitions with mixture of M1 and E2 components are important. Possibility of resolving the Ml component from dominant E2 in Coulomb dissociation data with precise angular distribution measurements has been considered. Based on a simulation calculation, its usefulness was examined and a new experiment has been proposed and approved at RIKEN. Less