We report on a new measurement of the 14N(p,γ)15O capture cross section at Ep=140 to 400 keV using the 400 kV LUNA accelerator facility at the Laboratori Nazionali del Gran Sasso (LNGS). The uncertainties have been reduced with respect to previous measurements and their analysis. We have analyzed the data using the R-matrix method and we find that the ground state transition accounts for about 15% of the total S-factor. The main contribution to the S-factor is given by the transition to the 6.79 MeV state. We find a total S(0)=1.7+/-0.2 keVb, in agreement with recent extrapolations. The result has important consequences for the solar neutrino spectrum as well as for the age of globular clusters

Abstract. The astrophysical S(E) factor of14 N(p, γ) 15 O has been measured for effective center-of-mass energies between E ef f = 119 and 367 keV at the LUNA facility using TiN solid targets and Ge detectors. The data are in good agreement with previous and recent work at overlapping energies. R-matrix analysis reveals that due to the complex level structure of 15 O the extrapolated S(0) value is model dependent and calls for additional experimental efforts to reduce the present uncertainty in S(0) to a level of a few percent as required by astrophysical calculations. .KvX -and γ ray spectroscopy -97.10.CvStellar structure and evolution PACS

The nuclear physics input from the 3 He(α, γ) 7 Be cross section is a major uncertainty in the fluxes of 7 Be and 8 B neutrinos from the Sun predicted by solar models and in the 7 Li abundance obtained in big-bang nucleosynthesis calculations. The present work reports on a new precision experiment using the activation technique at energies directly relevant to big-bang nucleosynthesis. Previously such low energies had been reached experimentally only by the prompt-γ technique and with inferior precision. Using a windowless gas target, high beam intensity and low background γ-counting facilities, the 3 He(α, γ) 7 Be cross section has been determined at 127, 148 and 169 keV center-of-mass energy with a total uncertainty of 4 %. The sources of systematic uncertainty are discussed in detail. The present data can be used in big-bang nucleosynthesis calculations and to constrain the extrapolation of the 3 He(α, γ) 7 Be astrophysical S-factor to solar energies. The 3 He(α, γ) 7 Be reaction is a critical link in the 7 Be and 8 B branches of the proton-proton (p-p) chain of solar hydrogen burning [1]. At low energies its cross section σ(E) (E denotes the center of mass energy, E α the 4 He beam energy in the laboratory system) can be parameterized by the astrophysical S-factor S(E) defined as. The 9.4 % uncertainty [3] in the Sfactor extrapolation to the solar Gamow energy (23 keV) contributes 8 % to the uncertainty in the predicted fluxes of solar neutrinos from the decays of 7 Be and 8 B [4]. The interior of the Sun, in turn, can be studied [4,5] by comparing this prediction with the data from neutrino detectors [6,7], which determine the 8 B neutrino flux with a total uncertainty as low as 3.5 % [7].Furthermore, the production of 7 Li in big-bang nucleosynthesis (BBN) is highly sensitive to the 3 He(α, γ) 7 Be cross section in the energy range E ≈ 160-380 keV [8], with an adopted uncertainty of 8 % [9]. Based on the baryon-to-photon ratio from observed anisotropies in the cosmic microwave background [10], network calculations predict primordial 7 Li abundances [11] that are significantly higher than observations [12,13]. A lower 3 He(α,γ)7 Be cross section at relevant energies may explain part of this discrepancy. The3 He(α,γ) 7 Be (Q-value: 1.586 MeV) reaction leads to the emission of prompt γ-rays, and the final 7 Be nucleus decays with a half-life of 53.22 ± 0.06 days, emitting a 478 keV γ-ray in 10.44 ± 0.04 % of the cases [14]. The cross section can be measured by detecting either the induced 7 Be activity (activation method) or the prompt γ-rays from the reaction (prompt-γ method). Previous activation studies [15,16,17,18] cover the energy range E = 420-2000 keV. Prompt γ-ray measurements [15,19,20,21,22,23,24] cover E = 107-2500 keV, although with limited precision at low energies.The global shape of the S-factor curve is well reproduced by theoretical calculations [25,26]. However, the slope has been questioned [26] for E ≤ 300 keV, where there are no high-precision data. Furthermore, a global analysis [3] ind...

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Publisher's Note: Astrophysical S factor of the 3 He(α, γ ) 7 Be reaction measured at low energy via detection of prompt and delayed γ rays [Phys. Rev. C 75, 065803 (2007)]

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Abstract. The transition between the Main Sequence and the Red Giant Branch in low mass stars is powered by the onset of CNO burning, whose bottleneck is 14 N(p, γ) 15 O. The LUNA collaboration has recently improved the low energy measurements of the cross section of this key reaction. We analyse the impact of the revised reaction rate on the estimate of the Globular Cluster ages, as derived from the turnoff luminosity. We found that the age of the oldest Globular Clusters should be increased by about 0.7−1 Gyr with respect to the current estimates.

The electron screening effect in the d(d,p)t reaction has been studied for deuterated metals, insulators, and semiconductors, i.e. 58 samples in total. As compared to measurements performed with a gaseous D 2 target, a large effect has been observed in most metals, while a small (gaseous) effect is found, e.g., for the insulators, semiconductors, and lanthanides. The periodic table provides the ordering of the observed small and large effects in the samples. An explanation of the large effects in metals is possibly provided by the classical plasma screening of Debye applied to the quasi-free metallic electrons. The data also provide information on the solubility of hydrogen in the samples. PACS. 25.10.+s Nuclear reactions involving few-nucleon systems -25.45.-z 2 H-induced reactions -95.30.-k Fundamental aspects of astrophysics