# THEORETICAL INVESTIGATIONS OF THE $^{12}$C($\alpha$,$\gamma$)$^{16}$O E2 CROSS SECTION

Abstract : The E2 component of the 12C(α,γ)16O cross section is investigated in three ways: by a microscopic cluster model, by R-matrix fits and by a combination of both. The microscopic calculation leads to an estimate of the S-factor at a typical energy of 300 keV of SE2(300 keV)≈ 50 keV-b for ground-state transitions. Cascade transitions to the and excited states of 16O are also studied. Then the S-factor is analyzed in the phenomenological R-matrix theory. We show that the background term plays a crucial role, and cannot be determined without ambiguity. Consequently only an upper limit on the extrapolated S-factor can be obtained [SE2(300 keV)< 190 keV-b]. Finally, we use the microscopic Asymptotic Normalization Constant (ANC) of the level, well known to be a cluster state to constrain the R-matrix analysis. This procedure strongly reduces the uncertainties on the R-matrix fits, and we end up with a recommended value of SE2(300 keV) = 42 ± 2 keV-b.
Document type :
Conference papers

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Submitted on : Thursday, January 15, 2009 - 2:43:15 PM
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### Citation

M. Dufour, P. Descouvemont. THEORETICAL INVESTIGATIONS OF THE $^{12}$C($\alpha$,$\gamma$)$^{16}$O E2 CROSS SECTION. First Workshop on State of the Art in Nuclear Cluster Physics, May 2008, Strasbourg, France. pp.2176 - 2181, ⟨10.1142/S0218301308011306⟩. ⟨in2p3-00353364⟩

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