arXiv subjects
Publications and source records attributed to A. Deltuva.
The method of screening and renormalization for including the Coulomb interaction in the framework of momentum-space integral equations is applied to the three- and four-body nuclear reactions. The Coulomb effect on the observables and the ability of the present nuclear potential models to describe the experimental data is discussed.
Momentum space three-body Faddeev-like equations are used to calculate elastic, transfer and charge exchange reactions resulting from the scattering of deuterons on 12C and 16O or protons on 13C and 17O; 12C and 16O are treated as inert cores. All possible reactions are calculated in the framework of the same model space. Comparison with previous calculations based on approximate methods used in nuclear reaction theory is discussed.
Full Faddeev-type calculations are performed for one-neutron knockout reaction of $^{14}$Be on proton target at 69 MeV/u incident energy. Inclusive transverse momentum distributions for the outgoing ($^{12}$Be + n) system and semi-inclusive cross sections are presented. A significant proton-core single scattering contribution emerges where the valence neutron has non zero angular momentum relative to the core. This indicates that distorted-wave impulse approximation is inadequate and the complete multiple scattering series must be taken into account for the considered reaction. The magnitude of the semi-inclusive cross section at quasifree scattering conditions is a clear signature of the angular momentum of the valence nucleon.
The method of screening and renormalization is used to include the Coulomb interaction between the charged particles in the description of few-body nuclear reactions. Calculations are done in the framework of Faddeev-type equations in momentum-space. The reliability of the method is demonstrated. The Coulomb effect on observables is discussed.
Two-body scattering is studied by solving the Lippmann-Schwinger equation in momentum space without angular-momentum decomposition for a local spin dependent short range interaction plus Coulomb. The screening and renormalization approach is employed to treat the Coulomb interaction. Benchmark calculations are performed by comparing our procedure with partial-wave calculations in configuration space for p-10Be, p-16O and 12C-10Be elastic scattering, using a simple optical potential model.
Low momentum two-nucleon interactions obtained with the renormalization group method and the similarity renormalization group method are used to study the cutoff dependence of low energy 3N and 4N scattering observables. The residual cutoff dependence arises from omitted short-ranged 3N (and higher) forces that are induced by the renormalization group transformations, and may help to estimate the sensitivity of various 3N and 4N scattering observables to short-ranged many-body forces.
Full Faddeev-type calculations are performed for $^{11}$Be breakup on proton target at 38.4, 100, and 200 MeV/u incident energies. The convergence of the multiple scattering expansion is investigated. The results are compared with those of other frameworks like Distorted Wave Impulse Approximation that are based on an incomplete and truncated multiple scattering expansion.
The four-nucleon bound state and scattering below three-body breakup threshold are described based on the realistic coupled-channel potential CD Bonn + $Δ$ which allows the excitation of a single nucleon to a $Δ$ isobar. The Coulomb repulsion between protons is included. In the four-nucleon system the two-baryon coupled-channel potential yields effective two-, three- and four-nucleon forces, mediated by the $Δ$ isobar and consistent with each other and with the underlying two-nucleon force. The effect of the four-nucleon force on the studied observables is much smaller than the effect of the three-nucleon force. The inclusion of the $Δ$ isobar is unable to resolve the existing discrepancies with the experimental data.
The continuum discretized coupled channels (CDCC) method is compared to the exact solution of the three-body Faddeev equations in momentum space. We present results for: i) elastic and breakup observables of d-12C at E_d=56 MeV, ii) elastic scattering of d-58Ni at E_d=80 MeV, and iii) elastic, breakup and transfer observables for 11Be+p at E_{11Be}/A=38.4 MeV. Our comparative studies show that, in the first two cases, the CDCC method is a good approximation to the full three-body Faddeev solution, but for the 11Be exotic nucleus, depending on the observable or the kinematic regime, it may miss out some of the dynamic three-body effects that appear through the explicit coupling to the transfer channel.
Four-body equations in momentum space are solved for neutron-$\He$, proton-$\Hh$, and deuteron-deuteron scattering; all three reactions are coupled. The Coulomb interaction between the protons is included using the screening and renormalization approach as it was recently done for proton-deuteron and proton-$\He$ scattering. Realistic interactions are used between nucleon pairs. For the first time fully converged results for the observables pertaining to the six different elastic and transfer reactions are obtained and compared with experimental data.
The four-body equations of Alt, Grassberger and Sandhas are solved, for the first time, for proton-${}^3\mathrm{He}$ scattering including the Coulomb interaction between the three protons using the method of screening and renormalization as it was done recently for proton-deuteron scattering. Various realistic two-nucleon potentials are used. Large Coulomb effects are seen on all observables. Comparison with data at different energies shows large deviations in the proton analyzing power but quite reasonable agreement in other observables. The effect of nucleon-nucleon magnetic moment interaction and correlations between $\pd$ and $\pHe$ analyzing powers are studied.
High precision vector and tensor analyzing powers of elastic deuteron-proton d+p scattering have been measured at intermediate energies to investigate effects of three-nucleon forces (3NF). Angular distribution in the range of 70-120 degree in the center-of mass frame for incident-deuteron energies of 130 and 180 MeV were obtained using the RIKEN facility. The beam polarization was unambiguously determined by measuring the 12C(d,alpha)10B(2+) reaction at 0 degree. Results of the measurements are compared with state-of-the-art three-nucleon calculations. The present modeling of nucleon-nucleon forces and its extension to the three-nucleon system is not sufficient to describe the high precision data consistently and requires, therefore, further investigation.
The four-body equations of Alt, Grassberger and Sandhas are solved for $\nH$ scattering at energies below three-body breakup threshold using various realistic interactions including one derived from chiral perturbation theory. After partial wave decomposition the equations are three-variable integral equations that are solved numerically without any approximations beyond the usual discretization of continuum variables on a finite momentum mesh. Large number of two-, three- and four-nucleon partial waves are considered until the convergence of the observables is obtained. The total $\nH$ cross section data in the resonance region is not described by the calculations which confirms previous findings by other groups. Nevertheless the numbers we get are slightly higher and closer to the data than previously found and depend on the choice of the two-nucleon potential. Correlations between the $A_y$ deficiency in $\nd$ elastic scattering and the total $\nH$ cross section are studied.
The Coulomb interaction between the two protons is included in the calculation of three-nucleon hadronic and electromagnetic reactions using screening and renormalization approach. Calculations are done using integral equations in momentum space. The reliability of the method is demonstrated. The Coulomb effect on observables is discussed.
The $α$-proton Coulomb interaction is included in the description of $α$-deuteron scattering using the screening and renormalization approach in the framework of momentum-space three-particle equations. The technical reliability of the method is demonstrated. Large Coulomb-force effects are found.
The AGS equations are solved for $n{}^3\mathrm{H}$ and $p{}^3\mathrm{He}$ scattering including the Coulomb interaction. Comparison with previous work confirms the accuracy of the calculation and helps clarify a number of issues related to the $n{}^3\mathrm{H}$ total cross section at the peak of the resonance region, as well as an $A_y$ deficiency in $p{}^3\mathrm{He}$. Calculations are fully converged in terms of $NN$ partial waves and involve no uncontrolled approximations.
High precision cross-section data of the deuteron-proton breakup reaction at 130 MeV deuteron energy are compared with the theoretical predictions obtained with a coupled-channel extension of the CD Bonn potential with virtual Delta-isobar excitation, without and with inclusion of the long-range Coulomb force. The Coulomb effect is studied on the basis of the cross-section data set, extended in this work to about 1500 data points by including breakup geometries characterized by small polar angles of the two protons. The experimental data clearly prefer predictions obtained with the Coulomb interaction included. The strongest effects are observed in regions in which the relative energy of the two protons is the smallest.
The Coulomb interaction between the protons is included in the description of proton-deuteron scattering using the screening and renormalization approach in the framework of momentum-space integral equations. Two new calculational schemes are presented that confirm the reliability of the perturbative approach for treating the screened Coulomb interaction in high partial waves, used by us in earlier works.