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Register a new userEffects of an induced three-body force in the incident channel of (d,p) reactions
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A widely accepted practice for treating deuteron breakup in $A(d,p)B$ reactions relies on solving a three-body $A+n+p$ Schrodinger equation with pairwise $A$-$n$, $A$-$p$ and $n$-$p$ interactions. However, it was shown in [Phys. Rev. C textbf{89}, 024605 (2014)] that projection of the many-body $A+2$ wave function into the three-body $A+n+p$ channel results in a complicated three-body operator that cannot be reduced to a sum of pairwise potentials. It contains explicit contributions from terms that include interactions between the neutron and proton via excitation of the target $A$. Such terms are normally neglected. We estimate the first order contribution of these induced three-body terms and show that applying the adiabatic approximation to solving the $A+n+p$ model results in a simple modification of the two-body nucleon optical potentials. We illustrate the role of these terms for the case of $^{40}$Ca($d,p$)$^{41}$Ca transfer reactions at incident deuteron energies of 11.8, 20 and 56 MeV, using several parameterisations of nonlocal optical potentials.
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We propose to use proton knockout reactions (p,2p) from a deeply bound orbit as a new probe into three-nucleon-force (3NF) effects. The remarkable advantage of using (p,2p) reaction is that we can choose an appropriate kinematical condition to probe the 3NF effects. We analyze (p,2p) reactions on a 40Ca target within the framework of distorted-wave impulse approximation with a g-matrix interaction based on chiral two- and three-nucleon forces. The chiral 3NF effects significantly change the peak height of the triple differential cross section of (p,2p) reaction. We also clarify the correspondence between the (p,2p) cross sections and the in- medium pp cross sections.
A new measurement of the p-d differential cross section at Ep= 1 MeV has been performed. These new data and older data sets at energies below the deuteron breakup are compared to calculations using the two-nucleon Argonne v18 and the three-nucleon Urbana IX potentials. A quantitative estimate of the capability of these interactions to describe the data is given in terms of a chi^2 analysis. The chi^2 per datum drastically improves when the three-nucleon interaction is included in the Hamiltonian.
With the increasing interest in using (d,p) transfer reactions to extract structure and astrophysical information, it is important to evaluate the accuracy of common approximations in reaction theory. Starting from the zero-range adiabatic wave model, which takes into account deuteron breakup in the transfer process, we evaluate the importance of the finite range of the n-p interaction in calculating the adiabatic deuteron wave (as in Johnson and Tandy) as well as in evaluating the transfer amplitude. Our study covers a wide variety of targets, as well as a large range of beam energies. Whereas at low beam energies finite-range effects are small (below 10%), we find these effects to become important at intermediate energies (20 MeV/u) calling for an exact treatment of finite range in the analysis of (d,p) reactions measured at fragmentation facilities.
We investigate the three-body Coulomb breakup of a two-neutron halo nucleus $^{11}$Li. We use the coupled-channel $^9$Li + $n$ + $n$ three-body model, which includes the coupling between last neutron states and the various $2p$-$2h$ configurations in $^9$Li due to the tensor and pairing correlations. The three-body scattering states of $^{11}$Li are described by using the combined methods of the complex scaling and the Lippmann-Schwinger equation. The calculated breakup cross section successfully reproduces the experiments. The large mixing of the s-state in the halo ground state of $^{11}$Li is shown to play an important role in explanation of shape and strength of the breakup cross section. In addition, we predict the invariant mass spectra for binary subsystems of $^{11}$Li. It is found that the two kinds of virtual s-states of $^9$Li-$n$ and $n$-$n$ systems in the final three-body states of $^{11}$Li largely contribute to make low-lying peaks in the invariant mass spectra. On the other hand, in the present analysis, it is suggested that the contributions of the p-wave resonances of $^{10}$Li is hardly confirmed in the spectra.
A new framework for $A(d,p)B$ reactions is introduced by merging the microscopic approach to computing the properties of the nucleon-target systems and the three-body $n+p+A$ reaction formalism, thus providing a consistent link between the reaction cross sections and the underlying microscopic structure. In this first step toward a full microscopic description, we focus on the inclusion of the neutron-target microscopic properties. The properties of the neutron-target subsystem are encapsulated in the Greens function which is computed with the Coupled Cluster theory using a chiral nucleon-nucleon and three-nucleon interactions. Subsequently, this many-body information is introduced in the few-body Greens Function Transfer approach to $(d,p)$ reactions. Our benchmarks on stable targets $^{40,48}$Ca show an excellent agreement with the data. We then proceed to make specific predictions for $(d,p)$ on neutron rich $^{52,54}$Ca isotopes. These predictions are directly relevant to testing the new magic numbers $N=32,34$ and are expected to be feasible in the first campaign of the projected FRIB facility.
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