We point out a simple relation between the nuclear vertex constant (NVC) and the overall normalization of the astrophysical S factor. Using predicted values of the NVC for the virtual decay of 'B 'Be + p, we find S|7 (0) = 17.6 eVb for 'Be(p, y)'B reactions, consistent with the low values extrapolated from direct capture measurements by Filippone et al. and by Vaughn et al. New possibilities, using proton transfer reactions, to measure the astrophysical S factor indirectly are proposed. PACS numbers: 25.40.Lw, 25.60.+v, 95.30.CqThe Be(p, y) B reaction at solar energies (E,~0 -20 keV, E, is the center of mass energy) plays an important unique role in the "solar neutrino puzzle" [1,2], since the high energy neutrinos from the subsequent P decay of B provide about 75% of the fiux detectable in the chlorine experiment and they are the only source to which the Kamiokande experiment is sensitive. Because
The disappearance of transverse collective flow for 40 Al collisions is studied with an improved Boltzmann-Uehling-Uhlenbeck equation. For collisions at impact parameters less than 3 fm, the predicted energy of balance, Ebai, is very sensitive to the in-medium nucleon-nucleon cross section, but insensitive to the equation of state. At larger impact-parameter collisions, the sensitivities to both the inmedium nucleon-nucleon cross section and the equation of state at subnuclear density become comparable. Comparisons with experimental data indicate an in-medium nucleon-nucleon cross section in the range of 25-45 mb.PACS numbers: 25.70.Np, 21.65.+f Flow, or the in-plane transverse momentum distribution of emitted particles, can carry important information about the reaction dynamics of nucleus-nucleus collisions and the nuclear equation of state. At incident energies of a few tens of MeV per nucleon, the interaction between nucleons is dominated by the attractive part of the nuclear mean field and the particles are deflected to negative angles [1], At energies of a few hundred MeV to 1 GeV/nucleon, the individual nucleon-nucleon scattering and the repulsive part of the nuclear mean field become important and the particles are emitted to positive angles [2][3][4]. At a certain intermediate incident energy, E^au referred to as the energy of balance [5][6][7], the attractive part and the repulsive part of the interactions are expected to balance each other and the flow crosses zero, changing from a negative sign at low energies to a positive sign at high energies [8,9]. Measurements of flow at different energies could, in principle, provide quantitative information concerning the nuclear equation of state at both low (attractive) and high (repulsive) densities. Significant efforts were made recently to study the equations of state at high densities [2-4, 8, 10-17]. Whether there is any noticeable sensitivity of flow to equations of state at low densities remains unclear.The disappearance of flow and its change to negative angles at a finite incident energy was first predicted by Bonasera and Csernai [8] based on a fluid-dynamical scaling study of LBL Bevalac data, before experimental data were available. This prediction was based on scaling violations due to viscosity [14,18] and due to the phase transition in the nuclear equation of state. The qualitative behavior of the energy dependence of flow was also studied by Bertsch et al. within the context of the Boltzmann-Uehling-Uhlenbeck (BUU) equation [9]. Because of the importance of Coulomb interactions and nuclear surface effects, and the significant dependence of Z?bai upon the masses of projectile and target, it was rather difficult to compare the earlier calculations with available data.To investigate the sensitivities of E^d\ to the equation of state and to the in-medium nucleon-nucleon cross section and to determine whether one can separate these dual dependences, we have performed improved BUU calculations for 40 Ar+ 27 Al collisions. In our improved calcula...
The Rapid Communications section is intended for the accelerated publication of important new results M.anuscripts submitted to this section are given priority in handling in the editorial once and in production AR. apid Communication in Physical Review C may be no longer than ftve printed pages and must be accompanied by an abstract Pag.e proofs are sent to authors.
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