Berlin 2005 – wissenschaftliches Programm

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HK: Physik der Hadronen und Kerne

HK 22: Postersitzung

HK 22.96: Poster

Montag, 7. März 2005, 16:30–18:00, TU MA141

Measurement of the ³He(α,γ)⁷Be cross section with ERNA — •Antonino Di Leva — Institut für Experimentalphysik III, Ruhr-Universität Bochum

The ³He(α,γ)⁷Be reaction plays an important role in the interpretation of the results of the solar neutrino experiments, since the estimate of the oscillation parameters relies on the solar neutrino spectrum, calculated by solar models. The high energy component in this spectrum is mainly produced by the decay of ⁷Be and ⁸B.

However uncertainty in the ³He(α,γ)⁷Be cross section is also one of the largest contributions to the uncertainty on primordial ⁷Li abundance in Big Bang Nucleosynthesis calculations. The latter can constrain the universe initial baryon density and the number of light neutrino flavors.

Measurements of the ³He(α,γ)⁷Be cross section have been performed detecting the capture gamma rays or measuring the activity of the synthesized ⁷Be. While the results of the two different approaches agree on the energy dependence of the astrophysical S factor, they disagree in the extrapolated S₃₄(0) value at a 3σ level, that suggests the presence of systematic errors in one or both techniques, or a non radiative component in the cross section.

A novel approach uses the European Recoil separator for Nuclear Astrophysics (ERNA), that can provide the simultaneous detection of both the capture gamma rays and the ⁷Be ions produced in the reaction. In this talk the experiment and results of preliminary measurements are discussed.

Supported by DFG(Ro 429/35-3), BMBF(05CL1PC1/1) and INFN