Comprehensive analysis of large α\alpha yields observed in 6^{6}Li induced reactions

Background: Large $\alpha$ yields have been reported over the years in reactions with $^{6}$Li and $^{7}$Li projectiles. Previous theoretical analyses have shown that the elastic breakup (EBU) mechanism (i.e., projectile breakup leaving the target in its ground state) is able to account only for a small fraction of the total $\alpha$ inclusive breakup cross sections, pointing toward the dominance of non-elastic breakup (NEB) mechanisms. Purpose: We aim to provide a systematic study of the $\alpha$ inclusive cross sections observed in nuclear reactions induced by $^{6}$Li projectiles. In addition to estimating the total $\alpha$ singles cross sections, it is our goal to evaluate angular and energy distributions of these $\alpha$ particles and compare with experimental data, when available. Method: We compute separately the EBU and NEB components of the inclusive breakup cross sections. For the former, we use the continuum-discretized coupled-channels (CDCC) method, which treats this mechanism to all orders. For the NEB part, we employ the the model proposed in the eighties by Ichimura, Austern and Vincent [Phys. Rev. C32, 432 (1982)], within the DWBA approximation. Results: Overall, the sum of the computed EBU and NEB cross sections is found to reproduce very well the measured singles cross sections. In all cases analyzed, we find that the inclusive breakup cross section is largely dominated by the NEB component. Conclusions: The presented method provides a global and systematic description of inclusive breakup reactions induced by $^{6}$Li projectiles. It provides also a natural explanation of the previously observed underestimation of the measured $\alpha$ yields by CDCC calculations. The method used here can be extended to other weakly-bound projectiles, including halo nuclei.Comment: 11 pages, 16 figures, fig. 12 updated; some typos correcte

The puzzle of complete fusion suppression in weakly-bound nuclei: a Trojan Horse effect?

Experimental studies of nuclear collisions involving light weakly-bound nuclei show a systematic suppression of the complete fusion cross section by $\sim$30\% with respect to the expectation for tightly bound nuclei, at energies above the Coulomb barrier. Although it is widely accepted that the phenomenon is related to the weak binding of these nuclei, the origin of this suppression is not fully understood. In here, we present a novel approach that provides the complete fusion for weakly bound nuclei and relates its suppression to the competition between the different mechanisms contributing to the reaction cross section. The method is applied to the $^{6,7}$Li+$^{209}$Bi reactions, where we find that the suppression of complete fusion is mostly caused by the flux associated with non-elastic breakup modes, such as the partial capture of the projectile (incomplete fusion), whereas the elastic breakup mode is found to play a minor role. Finally, we demonstrate that the large $\alpha$ yields observed in these reactions can be naturally explained as a consequence of a {\it Trojan Horse} mechanism.Comment: 6 pages, 4 figures. Accepted for publication in Phys. Rev. Letter

Global weak solutions for Kolmogorov-Vicsek type equations with orientational interactions

We study the global existence and uniqueness of weak solutions to kinetic Kolmogorov-Vicsek models that can be considered a non-local non-linear Fokker-Planck type equation describing the dynamics of individuals with orientational interactions. This model is derived from the discrete Couzin-Vicsek algorithm as mean-field limit \cite{B-C-C,D-M}, which governs the interactions of stochastic agents moving with a velocity of constant magnitude, i.e. the the corresponding velocity space for these type of Kolmogorov-Vicsek models are the unit sphere. Our analysis for $L^p$ estimates and compactness properties take advantage of the orientational interaction property meaning that the velocity space is a compact manifold

Symptom Information in Direct-to-Consumer Antidepressant Advertising and College Students\u27 Perception of the Lifetime Risk Depression

While consumers’ health cognition and behavior are likely formed through multiple influences, the current study focused on the effects of exposure to specific content elements in direct-to-consumer advertising. The study revealed that consumers’ exposure to the American Psychiatric Association’s (APA) diagnostic guideline has potential to reduce their perceived lifetime risk of depression and intention to consult a health professional to discuss the health issue. The study further revealed when an antidepressant ad mentioned a long list of symptoms, exposure to the diagnostic guideline reduced risk perception and consultation intention significantly, whereas in the presence of a short list of symptoms, the APA guideline had minimal impact