Köln 2004 – scientific programme

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HK: Physik der Hadronen und Kerne

HK 48: Nuclear and Particle Astrophysics IV

HK 48.6: Talk

Thursday, March 11, 2004, 17:45–18:00, F

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, which gave strong hints or reported about neutrino oscillations.
Indeed, the estimate of the oscillation parameters relies on the solar neutrino spectrum which is calculated by solar models: the relative rate of ³He(α,γ)⁷Be with respect to the rate of ³He(³He,2p)⁴He determines the high energy component of the solar neutrino spectrum, that is mostly produced by the decay of ⁷Be and ⁸B.

Previous measurements of the cross section for the ³He(α,γ)⁷Be reaction have been performed detecting the capture gamma rays or, alternatively, 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 of the techniques, or, possibly, a non radiative component in the cross section.

A novel approach to study this reaction relies on 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 its feasibility are discussed.