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Register a new userCovariant relativistic separable kernel approach for electrodisintegration of the deuteron at high momentum transfer
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The paper considers the electrodisintegration of the deuteron for kinematic conditions of the JLab experiment E-94-019. The calculations have been performed within the covariant Bethe-Salpeter approach with a separable kernel of nucleon-nucleon interactions. The results have been obtained using the relativistic plane wave impulse approximation and compared with experimental data and other models. The influence of nucleon electromagnetic form factors has been investigated.
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Two different methods of the covariant relativistic separable kernel construction in the Bethe-Salpeter approach are considered. One of them leads in the center-of-mass system of two particles to the quasipotential equation. The constructed 4-dimensional covariant functions are used to reproduce neutron-proton phase shifts for total angular momenta $J=0,1$. Obtained results are compared with other model calculations.
The electrodisintegration of the deuteron in the frame of the Bethe-Salpeter approach with a separable kernel of the nucleon-nucleon interaction is considered. This conception keeps the covariance of a description of the process. A comparison of relativistic and nonrelativistic calculations is presented. The factorization of the cross section of the reaction in the impulse approximation is obtained by analytical calculations. It is shown that the photon-neutron interaction plays an important role.
{bf Background} Deuteron induced reactions are widely used to probe nuclear structure and astrophysical information. Those (d,p) reactions may be viewed as three-body reactions and described with Faddeev techniques. {bf Purpose} Faddeev-AGS equations in momentum space have a long tradition of utilizing separable interactions in order to arrive at sets of coupled integral equations in one variable. However, it needs to be demonstrated that observables calculated based on separable interactions agree exactly with those based on nonseparable forces. {bf Methods} Momentum space AGS equations are solved with separable and nonseparable forces as coupled integral equations. {bf Results} Deuteron-alpha scattering is calculated via momentum space AGS equations using the CD-Bonn neutron-proton force and a Woods-Saxon type neutron(proton)-$^4$He force, for which the Pauli-forbidden S-wave bound state is projected out. Elastic as well as breakup observables are calculated and compared to results in which the interactions in the two-body sub-systems are represented by separable interactions derived in the Ernst-Shakin-Thaler (EST) framework. {bf Conclusions} We find that the calculations based on the separable representation of the interactions and the original interactions give results that are in excellent agreement. Specifically, integrated cross sections and angular distributions for elastic scattering agree within $approx$ 1%, which is well below typical experimental errors. In addition, the five-fold differential cross sections corresponding to breakup of the deuteron agree extremely well.
Within a covariant Bethe-Salpeter approach, the relativistic complex separable neutron-proton interaction kernel is proposed. The uncoupled partial-wave states with the total angular momentum $J$=0,1 are considered. The multirank separable potentials elaborated earlier are real-valued and, therefore, enable to describe the elastic part (phase shifts, low-energy parameters, etc.) of the scattering only. The description of the inelasticity parameter comes out of the imaginary part introduced into them. To obtain parameters of the complex potentials the elastic neutron-proton scattering experimental data up to 3 GeV are used. A signal of dybaryon resonances in the $^3P_0^+$ partial-wave state is discussed.
An approach aimed to extend the applicability range of non-relativistic microscopic calculations of electronuclear response functions is reviewed. In the quasielastic peak region the calculations agree with experiment at momentum transfers up to about 0.4 GeV/c while at higher momentum transfers, in the region about 0.4 - 1 GeV/c, a disagreement is seen. In view of this, to calculate the response functions a reference frame was introduced where dynamics relativistic corrections are small, and the results pertaining to it were transformed exactly to the laboratory reference frame. This proved to remove the major part of the disagreement with experiment. All leading order relativistic corrections to the transition charge operator and to the one--body part of the transition current operator were taken into account in the calculations. Furthermore, a particular model to determine the kinematics inputs of the non-relativistic calculations was suggested. This model provides the correct relativistic relationship between the reaction final-state energy and the momenta of the knocked-out nucleon and the residual system. The above mentioned choice of a reference frame in conjunction with this model has led to an even better agreement with experiment.
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