The S-factor at solar energies: The prompt γ experiment at LUNA

Abstract

The 3 He(α,γ) 7 Be process is a key reaction in both Big-Bang nucleosynthesis and p-p chain of Hydrogen Burning in Stars. A new measurement of the 3 He(α,γ) 7 Be cross section has been performed at the INFN Gran Sasso underground laboratory by both the activation and the prompt γ detection methods. The present work reports full details of the prompt γ detection experiment, focusing on the determi-nation of the systematic uncertainty. The final data, including activation measurements at LUNA, are compared with the results of the last generation experiments and two different theoretical models are used to obtain the S-factor at solar energies.

Nuclear Astrophysics in underground laboratories: the LUNA experiment

“…Finally, an updated reaction rate has been obtained, which is significantly higher than the one given in the most recent compilation of reaction rates [48]. As a consequence, new values for the ejected mass of 22 Ne and 23 Na in thermally pulsing AGB stars have been obtained with much reduced uncertainties [51].…”

“…In particular, the 3 He(α,γ) 7 Be reaction reaction controls the 7 Be and 8 B neutrinos and it is also fundamental for the production of 7 Li during the Big Bang Nucleosynthesis (BBN). The 3 He(α,γ) 7 Be reaction was studied at the LUNA2 accelerator by using both the gamma prompt detection [19,20] and the activation techniques [21,22] finding a perfect agreement within the two methods. This result was important not only to reduce the systematics, but also to solve the discrepancy previously shown in experiments based on the two different techniques.…”

“…In particular, the uncertainty on the 22 Ne(p,γ) 23 Na dominates the uncertainty of the entire cycle. As a matter of fact this reaction has several resonances below 400 keV and many of them were only given as upper limits based on indirect measurements.…”

Stellar Evolution and Modelling Stars

“…We note in passing that the cross sections of two important astrophysical factors (S 34 and S 1,14 ) have been updated by [41,42], and is highly recommended that the chosen set of thermonuclear reactions includes these latest values. Energy losses via neutrino emission (Eq.…”

Three-cluster model of radiative capture reactions in seven-nucleon systems. Effects of cluster polarization

“…The aim of the present work is to study how strongly the cluster polarization affects the cross sections or astrophysical S factor of the capture reactions 3 He(α, γ) 7 Be, 3 H(α, γ) 7 Li, 6 Li(p, γ) 7 Be, and 6 Li(n, γ) 7 Li in 7 Be and 7 Li nuclei. This investigation is stimulated by two circumstances.…”