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We discuss the most effective energy range for charged particle induced reactions in a plasma environment at a given plasma temperature. The correspondence between the plasma temperature and the most effective energy should be modified from the one given by the Gamow peak energy, in the presence of a significant incident-energy dependence in the astrophysical S-factor as in the case of resonant reactions. The suggested modification of the effective energy range is important not only in thermonuclear reactions at high temperature in the stellar environment, e.g., in advanced burning stages of massive stars and in explosive stellar environment, as it has been already claimed, but also in the application of the nuclear reactions driven by ultra-intense laser pulse irradiations.
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Gamow-Teller (GT) and spin-dipole (SD) strength distributions of four doubly magic nuclei $^{48}$Ca, $^{90}$Zr, $^{132}$Sn and $^{208}$Pb are studied by the self-consistent Hartree-Fock plus random phase approximation (RPA) method. The Skyrme forces SAMi and SAMi-T without/with tensor interactions are adopted in our calculations. The calculated strengths are compared with available experimental data. The RPA results of GT and SD strengths of all four nuclei show fine agreement with observed GT and SD resonances in energy. A small GT peak below the main GT resonance is better described by the Skyrme interaction SAMi-T with the tensor terms. The quenching factors for GT and SD are extracted from the comparisons between RPA results and experimental strengths. It is pointed out that the quenching effect on experimental SD peaks is somewhat modest compared with that on GT peaks in the four nuclei.
Data on the reaction $gamma pto K^+Lambda$ from the CLAS experiments are used to derive the leading multipoles, $E_{0+}$, $M_{1-}$, $E_{1+}$, and $M_{1+}$, from the production threshold to 2180,MeV in 24 slices of the invariant mass. The four multipoles are determined without any constraints. The multipoles are fitted using a multichannel $L+P$ model which allows us to search for singularities and to extract the positions of poles on the complex energy plane in an almost model-independent method. The multipoles are also used as additional constraints in an energy-dependent analysis of a large body of pion and photo-induced reactions within the Bonn-Gatchina (BnGa) partial wave analysis. The study confirms the existence of poles due to nucleon resonances with spin-parity $J^P = 1/2^-; 1/2^+$, and $3/2^+$ in the region at about 1.9,GeV.
The atomic nucleus capability of responding by hydromagnetic vibrations, that has been considered long ago by Hannes Alfven, is re-examined in the context of current development of nuclear physics and pulsar astrophysics.
Constituent quark models provide a reasonable description of the baryon mass spectra. However, even in the light- and strange-flavor sectors several intriguing shortcomings remain. Especially with regard to strong decays of baryon resonances no consistent picture has so far emerged, and the existing experimental data cannot be explained in a satisfactory manner. Recently first covariant calculations with modern constituent quark models have become available for all pi, eta, and K decay modes of the low-lying light and strange baryons. They generally produced a remarkable underestimation of the experimental data for partial decay widths. We summarize the main results and discuss their impact on the classification of baryon resonances into flavor multiplets. These findings are of particular relevance for future efforts in the experimental investigation of baryon resonances.
Solar neutrino capture cross-section by 127I nucleus has been studied with taking into account the influence of the resonance structure of the nuclear strength function S(E). Three types of isobaric resonances: giant Gamow-Teller, analog resonance and low-lying Gamow-Teller pigmy resonances has been investigated on the framework of self-consistent theory of finite Fermi systems. The calculations have been performed considering the resonance structure of the charge-exchange strength function S(E). We analyze the effect of each resonance on the energy dependence of the cross-section. It has been shown that all high-lying resonances should be considered. Neutron emission process for high energy nuclear excitation leads to formation 126Xe isotope. We evaluate contribution from various sources of solar neutrinos to the 126Xe/127Xe isotopes ratio formed by energetic neutrinos. 126Xe/127Xe isotope ratio could be an indicator of high-energy boron neutrinos in the solar spectrum. We also discuss the uncertainties in the often used Fermi-functions calculations.
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