Bochum 2009 – wissenschaftliches Programm

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HK: Fachverband Hadronen und Kerne

HK 50: Nuclear Astrophysics

HK 50.6: Vortrag

Mittwoch, 18. März 2009, 15:30–15:45, H-ZO 60

Measurement of the total cross section of ³He(α,γ)⁷Be with the recoil separator ERNA — •Antonino Di Leva — Institut für Experimentalphysik III Ruhr-Universität Bochum, Bochum, Germany — INFN Sezione di Napoli, Naples, Italy

The rate of ³He(α,γ)⁷Be plays a key role in the production of ⁷Li during the Big Bang Nucleosynthesis as well as in stellar hydrogen burning, where it has a strong influence on the high energy component of the solar neutrino spectrum.

In the last decades several experiments exploited either the detection of the prompt γ-rays or the off-line determination of the number of ⁷Be atoms collected in the target, in few cases both. The results of such experiments show some inconsistency, which hampers a determination of the ³He(α,γ)⁷Be cross section with the necessary precision and accuracy.

A new approach uses the recoil mass separator ERNA (European Recoil separator for Nuclear Astrophysics) for direct detection of the produced ⁷Be recoils. The total cross section has been measured in the energy region E_cm= 0.7 to 3.2 MeV. This approach is completely independent from previous techniques leading to substantially different systematic dependencies and, thus, independent information. In addition, off-beam activation and coincidence γ-ray measurements were performed at selected energies.

The experiment and its results, as well as the astrophysical consequences, are discussed.