Two-proton radioactivity and three-body decay. V. Improved momentum distributions

Nowadays quantum-mechanical theory allows one to reliably calculate the processes of 2p radioactivity (true three-body decays) and the corresponding energy and angular correlations up to distances of the order of 1000 fm. However, the precision of modern experiments has now become sufficient to indicate some deficiency of the predicted theoretical distributions. In this paper we discuss the extrapolation along the classical trajectories as a method to improve the convergence of the theoretical energy and angular correlations at very large distances (of the order of atomic distances), where only the long-range Coulomb forces are still operating. The precision of this approach is demonstrated using the "exactly" solvable semianalytical models with simplified three-body Hamiltonians. It is also demonstrated that for heavy 2p emitters, the 2p decay momentum distributions can be sensitive to the effect of the screening by atomic electrons. We compare theoretical results with available experimental data.Comment: 13 pages, 18 figure

Transport Model Simulations of Projectile Fragmentation Reactions at 140 MeV/nucleon

The collisions in four different reaction systems using $^{40,48}$Ca and $^{58,64}$Ni isotope beams and a Be target have been simulated using the Heavy Ion Phase Space Exploration and the Antisymmetrized Molecular Dynamics models. The present study mainly focuses on the model predictions for the excitation energies of the hot fragments and the cross sections of the final fragments produced in these reactions. The effects of various factors influencing the final fragment cross sections, such as the choice of the statistical decay code and its parameters have been explored. The predicted fragment cross sections are compared to the projectile fragmentation cross sections measured with the A1900 mass separator. At $E/A=140$ MeV, reaction dynamics can significantly modify the detection efficiencies for the fragments and make them different from the efficiencies applied to the measured data reported in the previous work. The effects of efficiency corrections on the validation of event generator codes are discussed in the context of the two models.Comment: 28 pages, 13 figure

One-nucleon transfer reactions and the optical potential

We provide a summary of new developments in the area of direct reaction theory with a particular focus on one-nucleon transfer reactions. We provide a status of the methods available for describing (d,p) reactions. We discuss the effects of nonlocality in the optical potential in transfer reactions. The results of a purely phenomenological potential and the optical potential obtained from the dispersive optical model are compared; both point toward the importance of including nonlocality in transfer reactions explicitly. Given the large ambiguities associated with optical potentials, we discuss some new developments toward the quantification of this uncertainty. We conclude with some general comments and a brief account of new advances that are in the pipeline.Comment: 7 pages, 5 figures, proceedings for the 14th International Conference on Nuclear Reaction Mechanisms, Varenna, June 201

Non-conformance with regulatory codes in the non-profit sector: accountability and the discursive coupling of means and ends

The concept of means-ends decoupling has recently been suggested as one consequence of the problems organizations face in trying to comply with institutional rules in contexts of institutional complexity. Such decoupling is characterised by the adoption, implementation and scrutiny of particular codes of practice which tend not to deliver the outcomes they were developed to produce. Recent scholarship focusing on this issue has suggested that such decoupling is a consequence of the “trade-off” organizations need to make between compliance and goal achievement most especially when the latter is difficult to evaluate. While recent scholarship has suggested that this tension might be mitigated by the activities of developers of compliance rules, in this paper, we explore how actors internal to an organization, in this case, two charitable organizations mitigate this tension via non-conformance with particular codes. We focus on how the process of accounting for non-conformance results in the discursive coupling of means and ends as actors creatively develop vocabularies of motive which respond to anticipated social criticism