Results 1 - 10 of 4682
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[en] The total and differential intensities of the two-neutrino double beta transition in 100Mo are calculated by taking into account experimental data on the charge-exchange reactions on 100Mo. It is shown that excited 1+ states should be considered in addition to the ground state of the intermediate nucleus 100Tc, which leads to the generalization of the SSD mechanism for the two-neutrino process.
[en] We discuss the usefulness of the double charge-exchange reactions (DCX) for the production of the neutron-rich Λ-hypernuclei. We believe the (π-, K+) reaction is one of the most promising DCX reactions, and propose to produce the neutron-rich Λ-hypernuclei, Λ6H and Λ9He, at the J-PARC 50 GeV PS by the reaction (J-PARC E10 experiment). The design of the experiment is presented. (author)
[en] The 19F(7Li,7Be)19O charge-exchange reaction at 52.2MeV incident energy has been studied at the INFN-LNS laboratory in Catania (Italy) using the MAGNEX spectrometer. Thanks to an algebraic ray-reconstruction technique and to a high-performing focal plane detector, high-resolution 19O energy spectra and angular distributions have been extracted. A theoretical analysis of the reaction in the framework of the Charge-Exchange Quasiparticle Random Phase Approximation (CEX-QRPA) has been done. The results of Distorted-Wave Born Approxiation (DWBA) calculations in a double folding scheme have been compared to the experimental angular distribution of the transition to the 19O state at 1.47MeV state and show a remarkable agreement both in magnitude and shape.
[en] We study chiral symmetry constraints on the Meson Exchange Current (MEC) contributions to the pion-nucleus Double Charge Exchange (DCX) scattering at low energies, employing the Wess-Zumino model. This allows us to include ρ and α1 as well as pions in the exchange current. We find: (1) The πN interactions are equivalent to those of Olsson and Turner, and are therefore consistent with our previous DCX work. (2) As in the case of the pion MEC, chiral symmetry leads to the existence of a class of diagrams for the π and/or α1 MEC whose contributions tend to cancel each other and which therefore must be calculated simultaneously. (3) Because of the cancellation the summed effects of the ρ or α1 MEC are much smaller than those of the pion MEC. These results verify in detail the argument given in our earlier paper for the dominance of ion over vector meson MEC in DCX
[en] The proposal for the experimental study of pion--nucleus scattering is considered including the theory, possible experiments, spectrometers, counting rate, other equipment, and the organization and budget. 11 references
[en] An analysis is made of the results of experimental and theoretical studies during the last ten years of a unique process: double charge exchange of pions on nuclei. On the one hand, the commissioning of meson factories and the use of new and more accurate experimental methods have led to the accumulation of rich and reliable material for not only light but also medium and heavy nuclei. On the other hand, the development and application of new microscopic theoretical approaches have led to a deepening of our ideas about the mechanism of these exotic reactions at low, intermediate, and high energies. The currently existing methods of theoretical investigation and all possible reaction mechanisms are considered. Particular attention is devoted to double charge exchange of pions on the lightest nuclei, for the theoretical description of which it is possible to use the well-developed methods for investigating few-particle systems. The experimental investigations of double-isobar analog and nonanalog transitions in the reaction of double charge exchange are systematized
[en] The near thermal charge transfer reaction of Ar+2 with N2 has been studied at total pressures below 10-7 Torr using a stored ion technique. Ar+2 ions produced by electron impact double ionization of Ar gas were selectively stored for times the order of seconds in a split-ring Penning-type ion trap. The decay with time of the initial ion sample number in a mixture of Ar and N2 gases was fit to the sum of two exponentials, corresponding to different reaction rates for the 3P and 1D low-lying Ar+2 levels. The observed Ar+2 number decrease is attributed to the double-charge transfer process Ar+2+N2→Ar+N2+2→Ar+N++N+ in accord with recent flow-tube measurements. A rate constant for the metastable Ar+2 (1D) level reaction with a value k(1D)=1.4 x 10-9 cm3/sec is obtained, using the previously measured rate constant for the Ar+2(3P) state