Influence of target deformation and deuteron breakup in (d,p) transfer reactions

Abstract

Background: The effect of core excitations in transfer reactions of the form A(d, p)B has been reexamined by some recent works, using the Faddeev/AGS reaction formalism. The effect was found to affect significantly the calculated cross sections and to depend strongly and non-linearly on the incident deuteron energy.Purpose: Our goal is to investigate these effects within a coupled-channels formulation of the scattering problem which, in addition of being computationally less demanding than the Faddeev counterpart, may help shed some light into the physical interpretation of the cited effects. Method:We use an extended version of the continuum-discretized coupled-channels (CDCC) method with explicit inclusion of target excitations within a coupled-channels Born approximation (CDCC-BA) formulation of the transfer transition amplitude. We compare the calculated transfer cross sections with those obtained with an analogous calculation omitting the effect of target excitation. We consider also an adiabatic coupled channels (ACC) method. Our working example is the 10 Be(d,p) 11 Be reaction.Results: We find that the two considered methods (CDCC-BA and ACC) reproduce fairly well the reported energy dependence of the core excitation effect. The main deviation from the pure three-body model calculation (i.e., omitting core excitations) is found to mostly originate from the destructive interference of the direct one-step transfer, and the two-step transfer following target excitation. Conclusions:The proposed method, namely, the combination of the CDCC method and the CCBA formalism, provides a useful and accurate tool to analyse transfer reactions including explicitly, when needed, the effect of target excitations and projectile breakup. The method could be useful for other transfer reactions induced by weakly-bound projectiles, including halo nuclei.

Models for nuclear reactions with weakly bound systems

“…It is found that the cross sections are no longer proportional to the spectroscopic factor and the departure from this proportionality increases with increasing incident energies, reaching a maximum at a deuteron energy of E d ≈60 MeV. Similar results and conclusions were achieved in [114] using two alternative methods. One uses an extended ADWA model, with a deformed adiabatic potential.…”

“…To study the scattering of three-body projectiles, such as Borromean nuclei, the Hamiltonian (105) must be generalized in order to take into account the three-body structure of the projectile. For example, for a two-neutron Borromean system with a structure of the form a = b + n + n one may use the Hamiltonian (114) H = H proj ( x, y)…”

Effects of an induced three-body force in the incident channel of ( d,p ) reactions

“…One way to deal with these induced three-body (I3B) terms is to explicitly include excited target states in the reaction model. This has, for example, been done within the CDCC [5,6] and Faddeev [7][8][9] approaches. However, these calculations include explicitly only a fraction of the model space needed to fully account for all the absorption known to be needed in the nucleon optical potentials.…”

Core-excitation effects in three-body breakup reactions studied using the Faddeev formalism

“…Such a behavior is in sharp contrast with transfer reactions [6,7,11,19,20] where dσ/dΩ(0 + ) obtained including the CX cannot be factorized into the SP differential cross section (dσ/dΩ) SP and the associated SF. The size of this CX effect may be characterized by the ratio R = dσ/dΩ(0 + ) SF(0 + ) · (dσ/dΩ) SP (7) or its deviation from unity D = (R − 1) × 100%.…”