# Increase in |S L | induced by channel coupling: The case of deuteron breakup

Abstract: For deuteron scattering from ${}^{58}$Ni at laboratory energies of 56, 79, and 120 MeV, we study the dynamic polarization potentials (DPPs) induced by $S$-wave and $D$-wave breakup (BU), separately and together, in order to gain insight into the nature of the DPP as well as a counterintuitive property: the existence of $L$ values for which the BU coupling increases $|{S}_{L}|$, a `wrong-way' effect. The effect is associated with the existence of emissive regions in the imaginary DPP, suggesting a connection with the nonlocal nature of the DPP. The same relationship was previously found for ${}^{6}$Li scattering, indicating a generic effect bearing on the dynamics of nuclear reactions.

## Summary (1 min read)

### Introduction

- Increase in |SL| induced by channel coupling: the case of deuteron scattering.
- The effect is associated with the existence of emissive regions in the imaginary DPP, suggesting a connection with the nonlocal nature of the DPP.

### II. CDCC CALCULATIONS

- Continuum discretized coupled channels (CDCC) calculations were carried out, with the standard formalism using the code FRESCO [8], in order to study the contribution of deuteron breakup (BU) to the effective deuteron-nucleus interaction.
- Calculations included coupling to the S-wave continuum (SBU), the D-wave continuum (DBU), and both continua (SDBU) since the authors had observed different degrees of WW for the SBU and SDBU cases.
- The measured experimental data were fitted in a grid search by the elastic scattering angular distributions for SDBU calculations.
- The last two columns of this table give the volume integrals of the resulting deuteronnucleus folded potential, the ‘bare potential’ for that energy.

### IV. CALCULATION OF DPP

- For each energy, the bare potential is subtracted from the potential found by inverting [10,11] the elastic channel S matrix, SL, from the CDCC calculations.
- The SBU column presents the results for the case with S-wave breakup channels only, the DBU column is for D-wave breakup, and the SDBU column is for both S-wave and D-wave continua included and coupled together.
- The sum has some significance for JR and JI, but the authors include the sums for RR and RI as well, and comment on the results.
- Concerning the real DPP, the authors note that for SBU it is mostly attractive, with only weak surface repulsion, whereas for DBU it is much more repulsive in the surface.
- The authors postulate a connection between this emissiveness and the tendency for a WW effect that is most pronounced at the lowest energy.

### V. GENERIC EFFECT: COMPARISON WITH 6Li ON 12C

- The above calculations were prompted by the results of Ref. [1] where a relationship between WW effects and emissive regions appeared in the DPP due to breakup of 6Li on 12C.
- The authors intend to carry out ψ-potential studies [15,16] of these and similar cases to investigate the spatial distribution of absorption and emission within the target nucleus.
- This might throw light on the causation of WW and its relationship to Austern’s account [7] of nonlocality in nuclear interactions, a fundamental aspect nuclear interaction dynamics.

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