Coupling effects in proton scattering from ⁴⁰Ca

Recent studies showed that neutron pickup makes a substantial contribution to the proton optical model potential (OMP) for light, mostly halo, target nuclei. Here, we extend those studies to a more “normal” target nucleus: 40Ca. We present coupled reaction channel (CRC) calculations with the coupling of 30.3 MeV incident protons to deuterons and up to 12 states of 39Ca. The proton elastic scattering S matrix from the CRC calculation is subject to Slj→V(r)+l·s VSO(r) inversion and the bare potential of the CRC calculation is subtracted, directly yielding a local and L-independent representation of the dynamic polarization potential (DPP). This is appropriate for comparison with phenomenological OMPs and local OMPs derived in local density folding models. The real-central part of the DPP is repulsive and cannot be represented as a uniform normalization of the bare potential, changing the rms radius. A series of model calculations reveal the dependence of the DPP on a range of parameters illuminating (i) departures of nucleon potentials of specific nuclei from global properties, (ii) the generation of repulsion, and (iii) the requirements for all-order CRC and deuteron breakup. Light is thrown on the nonlocality of the underlying DPP

Strong pickup-channel coupling effects in proton scattering: the case of p + Be-10

The dynamic polarization potential (DPP) contribution to the effective proton-nucleus interaction, that is due to the coupling of deuteron channels, is evaluated by applying $S_{lj} \to V(r)$ inversion to the elastic channel $S$-matrix from coupled reaction channel calculations of proton elastic scattering. This was done for protons scattering from $^{10}$Be at 12, 13, 14, 15, and 16 MeV; non-orthogonality corrections were included. We find a consistent pattern of a repulsive real and an absorptive imaginary DPP, with the absorption shifted to a larger radius. This is consistent with what has been found for proton scattering from the neutron skin nucleus $^8$He. The DPP is not of a form that can be represented by a renormalization of the bare potential, and has properties suggesting an underlying non-local process. We conclude that deuteron channels cannot be omitted from a full theoretical description of the proton-nucleus interaction (optical potential).Comment: 14 pages, 4 figures, RevTeX4, accepted by Phys Rev

Breakup coupling effects on near-barrier ⁶Li, ⁷Be and ⁸B + ⁵⁸Ni elastic scattering compared

New data for near-barrier 6Li, 7Be and 8B + 58Ni elastic scattering enable a comparison of breakup coupling effects for these loosely-bound projectiles. Coupled Discretised Continuum Channels (CDCC) calculations suggest that the large total reaction cross sections for 8B + 58Ni are dominated by breakup at near-barrier energies, unlike 6Li and 7Be where breakup makes a small contribution. In spite of this, the CDCC calculations show a small coupling influence due to breakup for 8B, in contrast to the situation for 6Li and 7Be. An examination of the S matrices gives a clue to this counter-intuitive behaviour

Climate Ready Estuaries - COAST in Action: 2012 Projects from Maine and New Hampshire

In summer 2011 the US EPA’s Climate Ready Estuaries program awarded funds to the Casco Bay Estuary Partnership (CBEP) in Portland, Maine, and the Piscataqua Region Estuaries Partnership (PREP) in coastal New Hampshire, to further develop and use COAST (COastal Adaptation to Sea level rise Tool) in their sea level rise adaptation planning processes. The New England Environmental Finance Center worked with municipal staff, elected officials, and other stakeholders to select specific locations, vulnerable assets, and adaptation actions to model using COAST. The EFC then collected the appropriate base data layers, ran the COAST simulations, and provided visual, numeric, and presentation-based products in support of the planning processes underway in both locations. These products helped galvanize support for the adaptation planning efforts. Through facilitated meetings they also led to stakeholders identifying specific action steps and begin to determine how to implement them

Combined Effects of Topdressing, Cultivation, and Carfentrazone-ethyl on Silvery-Thread Moss Infestation

The greatest reduction in silvery-thread moss (STM; Bryum argenteum Hedw.) cover was achieved when cultivation treatments were used in conjunction with carfentrazone

Remarkable independence of dynamical polarization potentials of the underlying potential

The dynamical polarization potential (DPP) generated by the coupling of specific reaction channels to the elastic channel can be determined by inverting the elastic channel S matrix from a coupled reaction channel (CRC) calculation. The “bare” potential of the CRC calculation is then subtracted from the inverted potential to yield a local representation of the DPP. Here we study the extent to which the DPP calculated in this way depends upon the bare potential. We find that the DPP caused by coupling to pickup channels, for 30.3 MeV protons scattering from 40Ca, turns out to be qualitatively and almost quantitatively unaffected by substantial changes in the bare potential. This puts the properties of DPPs established in this way on a firmer foundation

Pickup coupling contribution to the optical model potential for 30.3 MeV protons and neutrons on⁴⁰Ca

We study the dynamic polarization potentials (DPPs) for 30.3 MeV protons and neutrons scattering from40Ca that are generated by the coupling to deuteron channels. In this way we resolve unexpected differences from the general properties of such DPPs found in similar cases for lighter targets. It turns out that the contribution of particular states to the real part can change considerably with Q value, coming close to changing sign. One consequence is the surprising result presented in Mackintosh and Keeley [Phys. Rev. C 97, 069901(E) (2018)], which is investigated here. The Q-value dependence of the DPPs also contributes to a substantial difference between the optical model potential for protons and neutrons, there being substantially different Q values for 40Ca (n, d) and 40Ca (p, d) pickup reactions. The DPP calculations also enable a study of the dynamical nonlocality (distinct from exchange nonlocality) arising from pickup coupling. The characteristic properties of the DPPs for both protons and neutrons arising from nucleon pickup are also presented for incident nucleons at 25, 35, 40, and 45 MeV. All these properties vary with energy in a consistent way, including a change in the rms radius of the real potential, which, together with the general undularity of the DPP, shows that the pickup contributions cannot be represented by renormalizing a folding model potential

Dynamic polarization potential and dynamical nonlocality in nuclear potentials: nucleon-nucleus potential

Background: Of the two sources of nonlocality in nucleon-nucleus and nucleus-nucleus interactions, knock-on exchange and dynamically generated, almost all papers referring to nonlocality mention only the first. Purpose: Our purpose is threefold: to demonstrate a method for including dynamical nonlocality, for which a simple prescription (like the Perey factor for exchange nonlocality) is unknown, within distorted wave Born approximation (DWBA) calculations; to identify signatures of dynamic nonlocality and illuminate the extent to which the presence of such nonlocality can influence the extraction of spectroscopic information from direct reactions, and more generally, to increase our understanding of nucleus-nucleus interactions. Methods: After reviewing existing indications of dynamically induced nonlocality, DWBA transfer calculations are presented which compare results involving dynamically nonlocal potentials with those involving their local equivalents. The dynamical nonlocal potentials are generated in situ by the presence of channel coupling and the local equivalents are generated by inversion of the corresponding coupled channel elastic S matrix. This method obviates the need for solving integro-differential equations for including nonlocal potentials in DWBA. Results: The coupling of nucleons to collective states of the target nucleus induces dynamical nonlocality in the nucleon-nucleus interaction that has a significant effect on (p,d) reactions at energies relevant to spectroscopic studies. Conclusions: A method for studying the contribution of dynamically induced nonlocality in nuclear interactions has been demonstrated. Dynamically induced nonlocality should not be overlooked in the analysis of direct reactions. The method can also be applied to dynamic nonlocality due to projectile excitation

Cluster Model for Near-barrier Fusion Induced by Weakly Bound and Halo Nuclei

The influence on the fusion process of coupling transfer/breakup channels is investigated for the medium weight $^{6,7}$Li+$^{59}$Co systems in the vicinity of the Coulomb barrier. Coupling effects are discussed within a comparison of predictions of the Continuum Discretized Coupled-Channels model. Applications to $^{6}$He+$^{59}$Co induced by the borromean halo nucleus $^{6}$He are also proposed.Comment: 5 pages, 3 figures, FINUSTAR2 Conference, Aghios Nikolaus, Crete, Greece. 10-14 September 200