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We present results for spectroscopic factors of the outermost shells in 40 Ca and 208 Pb, which have been derived from the comparison between the available quasielastic (e, e ′ p) data from NIKHEF-K and the corresponding calculated cross-sections obtained within a fully relativistic formalism. We include exactly the effect of Coulomb distortion on the electron wave functions and discuss its role in the extraction of the spectroscopic factors from experiment.Without any adjustable parameter, we find spectroscopic factors of about 70%, consistent with theoretical predictions. We compare our results with previous relativistic and nonrelativistic analyses of (e, e ′ p) data. In addition to Coulomb distortion effects we discuss different choices of the nucleon current operator and also analyze the effects due to the relativistic treatment of the outgoing-distorted and bound nucleon wave functions.

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We investigate the role of relativistic and nonrelativistic optical potentials used in the analysis of (e, e ′ p) data. We find that the relativistic calculations produce smaller (e, e ′ p) cross sections even in the case in which both relativistic and nonrelativistic optical potentials fit equally well the elastic proton-nucleus scattering data. Compared to the nonrelativistic impulse approximation, this effect is due to a depletion in the nuclear interior of the relativistic nucleon current, which should be taken into account in the nonrelativistic treatment by a proper redefinition of the effective current operator. 25.30.Fj, 24.10.Jv, 21.10.Jx

We assume an environment of neutrons and α-particles of given density and temperature where nuclear syntheses into 6 He, 9 Be and 12 C are possible. We investigate the resulting relative abundance as a function of density and temperature. When the relative abundance of α-particles Yα is between 0.4 and 0.9, or larger than 0.9, the largest production is 9 Be or 12 C, respectively. When Yα < 0.4 6 He is mostly frequently produced for temperatures above about 2 GK whereas the 9 Be production dominates at smaller temperatures.

We investigate the low-temperature reaction rates for radiative capture processes of three particles. We compare direct and sequential capture mechanisms and rates using realistic phenomenological parametrizations of the corresponding photodissociation cross sections. Energy conservation prohibits sequential capture for energies smaller than that of the intermediate two-body structure. A finite width or a finite temperature allows this capture mechanism. We study generic effects of positions and widths of two-and three-body resonances for very low temperatures. We focus on nuclear reactions relevant for astrophysics, and we illustrate with realistic estimates for the α-α-α and α-α-n radiative capture processes. The direct capture mechanism leads to reaction rates which for temperatures smaller than 0.1 GK can be several orders of magnitude larger than those of the NACRE compilation. PACS. 21.45.-v Few-body systems -25.40.Lw Radiative capture -26.20.-f Hydrostatic stellar nucleosynthesis

The hyperspherical adiabatic expansion is combined with complex scaling and used to calculate low-lying nuclear resonances of 12 C in the 3α-model. We use Ali-Bodmer potentials and compare results for other potentials α − α with similar 8 Be-properties. A three-body potential is used to adjust the 12 Cresonance positions to desired values extending the applicability of the method to many-body systems decaying into three α-particles. For natural choices of three-body potentials we find 14 resonances below the proton separation threshold, i.e. two 0 + , three 2 + , two 4 + , one of each of 1 ± , 2 − , 3 ± , 4 − , and 6 + . The partial wave decomposition of each resonance is calculated as function of hyperradius. Strong variation is found from small to large distance. Connection to previous experimental and theoretical results are discussed and agreements as well as disagreements are emphasized.PACS. 21.45.+v Few-body systems -21.60.Gx Cluster models -25.70.Ef Resonances -27.20.+n. 6 <= A <= 19