Reaction channel contributions to the triton + Pb208 optical potential

Abstract

Background: Well-established coupled channel and coupled reaction channel (CRC) processes make contributions to elastic scattering that are not included in standard folding models of the optical model potential (OMP). Such contributions have been established for $^{3}\mathrm{He}$ interacting with $^{208}\mathrm{Pb}$ but the corresponding contributions for $^{3}\mathrm{H}$ are expected to be different, particularly for pickup coupling.Purpose: To establish and characterize the contribution to the interaction potential between $^{3}\mathrm{H}$ and $^{208}\mathrm{Pb}$ that is generated by coupling to proton pickup (outgoing $^{4}\mathrm{He}$) channels; also to study the contribution of collective states and identify effects of dynamical nonlocality due to these couplings.Methods: CRC calculations, including coupling to collective states, will provide the elastic channel $S$-matrix ${S}_{lj}$ resulting from the included processes. Inversion of ${S}_{lj}$ will produce the local potential that yields, in a single channel calculation, the elastic scattering observables from the coupled channel calculation. Subtracting the bare potential from the inverted CRC potential yields a local and $l$-independent representation of the dynamical polarization potential (DPP). From the DPPs due to a range of combinations of channel couplings, the influence of dynamically generated nonlocality can be identified.Results: Coupling to $^{4}\mathrm{He}$ channels makes a smaller contribution to the $^{3}\mathrm{H}$ interaction than it does for incident $^{3}\mathrm{He}$. On the other hand coupling to inelastic channels makes a greater contribution than it does for $^{3}\mathrm{He}$. The nonadditivity of the DPPs implies their dynamical nonlocality.Conclusions: The DPPs established here challenge the notion that folding models, in particular local density models, provide a satisfactory description of elastic scattering of $^{3}\mathrm{H}$ from nuclei. Coupling to proton pickup channels induces dynamical nonlocality in the $^{3}\mathrm{H}$ OMP with implications for direct reactions involving $^{3}\mathrm{H}$. Departures from a smooth radial form for the $^{3}\mathrm{H}$ OMP should be apparent in high quality fits to suitable elastic scattering data. Future theories of the interaction of $^{3}\mathrm{H}$ with nuclei should include some representation of outgoing $^{4}\mathrm{He}$.