Model For Nucleon-nucleon Interaction Research Articles

On the separability of microscopic optical model potentials and emerging bell-shape Perey–Buck nonlocality

After nearly sixty years since its introduction, the phenomenological bell-shape Perey-Buck spatial nonlocality in the optical model potential for nucleon-nucleus scattering has remained unaccounted for from a microscopic standpoint. In this article we provide a quantitative account for such nonlocality considering fully nonlocal optical potentials in momentum space. The framework is based on a momentum-space in-medium folding model, where infinite nuclear matter $g$ matrices in Brueckner-Hartree-Fock approximation are folded to the target one-body mixed density. The study is based on chiral next-to-next-to-next-to-leading order (N3LO) as well as Argonne $v_{18}$ nucleon-nucleon bare interaction models. Applications focus on $^{40}$Ca($p,p$) scattering at beam energies in the range 11-200 MeV, resulting in the identification of a separable structure of the momentum-space optical potential of a form we coin as $JvH$, with a nonlocality form factor as one of its terms. The resulting nonlocaliy form factor features a bell-shape with nonlocality range $\beta$ between 0.86 and 0.89 fm, for both proton and neutron beams at energies below 65 MeV. An analytic toy model is introduced to elucidate the underlying mechanism for the nonlocality in the optical model, providing an estimate of its range based on the Fermi motion of the target nucleons and the long-range part of the $NN$ interaction.

Four-body Faddeev-type calculation of the K̅NNN system

A quasi-bound state in the K̅NNN system caused by strong interactions was studied using dynamically exact four-body Faddeev-type equations. Binding energy and width of the K−ppn state were calculated using three antikaon-nucleon and three nucleon-nucleon interaction models.

12C(e,e'pN) measurements of short range correlations in the tensor-to-scalar interaction transition region

High-momentum configurations of nucleon pairs at short-distance are probed using measurements of the 12C(e,e′p) and 12C(e,e′pN) reactions (where N is either n or p), at high-Q2 and xB>1.1. The data span a missing-momentum range of 300–1000 MeV/c and are predominantly sensitive to the transition region of the strong nuclear interaction from a Tensor to Scalar interaction. The data are well reproduced by theoretical calculations using the Generalized Contact Formalism with both chiral and phenomenological nucleon-nucleon (NN) interaction models. This agreement suggests that the measured high missing-momentum protons up to 1000 MeV/c predominantly belong to short-ranged correlated (SRC) pairs. The measured 12C(e,e′pN) / 12C(e,e′p) and 12C(e,e′pp) / 12C(e,e′pn) cross-section ratios are consistent with a decrease in the fraction of proton-neutron SRC pairs and increase in the fraction of proton-proton SRC pairs with increasing missing momentum. This confirms the transition from an isospin-dependent tensor NN interaction at ∼400 MeV/c to an isospin-independent scalar interaction at high-momentum around ∼800 MeV/c as predicted by theoretical calculation.

On a Quasi-Bound State in the $$\pmb {{ K^- d}}$$ System Caused by Strong Interactions

It was found that $NN$ potential could influence the results of the quasi-bound state search in the $K^- d$ system, where the corresponding pole is situated close to the threshold. Three-body Faddeev-type calculations of the $\bar{K}NN - \pi \Sigma N$ system performed with a new model of nucleon-nucleon interaction predict the existence of the quasi-bound $K^- d$ state caused by strong interactions. Its binding energy is small ($1-2$ MeV), while the width is comparable with the width of the $K^- pp$ quasi-bound state ($40-60$ MeV).

The scattering cross sections for6,7Li +nreactions

We investigate the continuum-discretized coupled-channel analysis to the integrated elastic and inelastic scattering cross sections for 6,7 Li + n reactions. We used the Jeukenne- Lejeune-Mahaux effective nucleon-nucleon interaction and optical model potential at incident neutron energies below and above 10 MeV, respectively. The calculated elastic and inelastic scattering cross sections with observed incident energies are almost in good agreement with experimental and evaluated data. cross sections for 6,7 Li at incident neutron energies below 10 MeV by using optical model potential (OMP) (7,8) and above 10 MeV by using JLM. We adjust the normalization constants for the OMP, because the agreement of the calculated cross sections with the data in very low incident energies of the neutron is insufficient without any adjustments. The energy dependent normalization constants, real part λv and imaginary part λw, of the OMP and JLM are determined explicitly from the integrated elastic cross section data, respectively. Comparing the results of calculations with experimental data, we discuss that the present CDCC calculations, which reproduce the experimental data observed in incident energies higher than 10 MeV with the single folding potential of the JLM and in lower energies with introducing the normalization factors for the cluster folding potential of the OMP.

Calculation of multichannel reactions in the four-nucleon system above breakup threshold.

The exact four-body equations of Alt, Grassberger, and Sandhas are solved for neutron-3He and proton-3H scattering in the energy regime above the four-nucleon breakup threshold. Cross sections and spin observables for elastic, transfer, charge-exchange, and breakup reactions are calculated using realistic nucleon-nucleon interaction models, including the one with effective many-nucleon forces due to explicit Δ-isobar excitation. The experimental data are described reasonably well with only few exceptions such as vector analyzing powers.

Nucleon-nucleon interaction: A typical/concise review

Nearly a recent century of work is divided to Nucleon-Nucleon (NN) interaction issue. We review some overall perspectives of NN interaction with a brief discussion about deuteron, general structure and symmetries of NN Lagrangian as well as equations of motion and solutions. Meanwhile, the main NN interaction models, as frameworks to build NN potentials, are reviewed concisely. We try to include and study almost all well-known potentials in a similar way, discuss more on various commonly used plain forms for two-nucleon interaction with an emphasis on the phenomenological and meson-exchange potentials as well as the constituent-quark potentials and new ones based on chiral effective field theory and working in coordinate-space mostly. The potentials are constructed in a way that fit NN scattering data, phase shifts, and are also compared in this way usually. An extra goal of this study is to start comparing various potentials forms in a unified manner. So, we also comment on the advantages and disadvantages of the models and potentials partly with reference to some relevant works and probable future studies.

Final state interaction effects in electrodisintegration of the deuteron in the Bethe-Salpeter approach

The electrodisintegration of the deuteron is considered within a relativistic model of nucleon-nucleon interaction based on the Bethe-Salpeter approach with a separable interaction kernel. The exclusive cross section is calculated within the impulse approximation under various kinematic conditions. Final state interactions between the outgoing nucleons are taken into account. The comparison of nonrelativistic and relativistic calculations is presented. Partial-wave states of the neutron-proton pair with total angular momentum $J=0,1$ are considered.

Cross section of the deuteron–proton breakup as a probe of three-nucleon system dynamics

Modern nucleon-nucleon interaction models can be probed quantitatively in the three-nucleon environment by comparing predictions based on rigorous solutions of the Faddeev equations with the measured observables. Proper description of the experimental data can be achieved only if the dynamical models include subtle effects of suppressed degrees of freedom, effectively introduced by means of genuine three-nucleon forces. A large set of high precision, exclusive cross-section data for the 1H(d,pp)n breakup reaction at 130 MeV, contributes significantly to constrain the physical assumptions underlying the theoretical interaction models. Comparison of nearly 1800 cross section data points with the predictions using nuclear interactions generated in various ways, allowed to establish for the first time a clear evidence of importance of the three-nucleon forces in the breakup process. Moreover, the results, supplemented by a set of cross sections from another dedicated experiment, confirmed predictions of sizable Coulomb force influences in this reaction.

Precision studies of few-nucleon system dynamics

Modern nucleon-nucleon interaction models can be probed quantitatively in the three-nucleon (3N) environment by comparing predictions based on rigorous solutions of the Faddeev equations with the measured observables. Proper description of the experimental data can be achieved only if the models are supplemented with additional dynamical ingredients: subtle traces of suppressed degrees of freedom, e_ectively introduced by means of genuine three-nucleon forces and e_ects of the Coulomb force. As an example of precision studies of 3N system dynamics, new generation measurements of the 1H(∼d,pp)n breakup reaction at 130 MeV are considered. Large sets of high accuracy, exclusive cross-section and analyzing power data acquired in these projects contribute significantly to constrain the physical assumptions underlying the theoretical interaction models. Comparisons of the cross-section data with the predictions using nuclear interactions generated in various ways, allowed to establish importance of including both, the 3N and the Coulomb forces to strongly improve description of the whole data set. Discrepancies observed in reproducing the analyzing power data hint at still persisting incompleteness of modeling the 3N system interaction dynamics.

Quasifree scattering of electrons on light nuclei and some properties of nuclear interaction

The status of experimental and theoretical studies of the position of the quasifree cross-section maximum in the A(e, e′) reaction is discussed. The dependence of the shift of the maximum relative to the elastic eN-scattering on the kinematic conditions of measurements is considered. The possibilities of using the data for the selection of realistic models of nucleon-nucleon interaction and dynamic short-range correlations in nuclei, as well as for determining the parameters of the nucleon-nucleus potential and the nucleon effective mass, are analyzed.

Studies of the three-nucleon system dynamics: Cross sections of the deuteron-proton breakup at 130 MeV

The three-nucleon system is the simplest non-trivial testing ground in which the quality of modern nucleon-nucleon interaction models, as well as additional dynamical ingredients referred to as three-nucleon forces, can be probed quantitatively by means of a rigorous technique of solving the Faddeev equations. A large set of high precision, exclusive cross-section data for the (1)H((d) over right arrow, pp)n breakup reaction at 130 MeV was obtained at KVI, Groningen. It allowed to establish for the first time a clear evidence of the three-nucleon force contributions to the cross sections of the breakup process and to confirm recent predictions of sizable influences of the Coulomb force in this reaction.

Is a physically observable tetraneutron resonance compatible with realistic nuclear interactions?

The possible existence of four-neutron resonances close to the physical energy region is explored. Faddeev-Yakubovsky equations have been solved in configuration space using realistic nucleon-nucleon interaction models. Complex scaling and analytical continuation in the coupling constant methods were used to follow the resonance pole trajectories, which emerge out of artificially bound tetraneutron states. The final pole positions for four-neutron states lie in the third energy quadrant with negative real energy parts and should thus not be physically observable.

Nuclei of Double-Charm Hyperons

The ground states of double-charm hyperons form a spin 1/2 isospin 1/2 multiplet analogous to that of nucleons. Their main strong interaction may be inferred directly from the corresponding nucleon-nucleon interaction by multiplication of the interaction components by the appropriate fractional difference between interaction strengths for pairs of light flavor quarks and pairs of triplets, e.g. nucleons, of light flavor quarks. By construction of the interaction between the recently discovered double-charm hyperons by this method from several realistic nucleon-nucleon interaction models it is shown that double-charm hyperons are likely to form bound (or possibly meta-stable) states akin to the deuteron in the spin triplet state. Double beauty baryons would form corresponding deeply bound states. Nucleons and double charm (beauty) hyperons will also form bound states. The existence of hypernuclei with double-charm and double-beauty hyperons, which are stable against the strong decay, is very likely.

Three-neutron resonance trajectories for realistic interaction models

Three-neutron resonances are investigated using realistic nucleon-nucleon interaction models. The resonance pole trajectories are explored by first adding an additional interaction to artificially bind the three-neutron system and then gradually removing it. The pole positions for the three-neutron states up to $J=5/2$ are localized in the third energy quadrant---$\mathrm{Im}\phantom{\rule{0.2em}{0ex}}(E)\ensuremath{\leqslant}0,\phantom{\rule{0.3em}{0ex}}\mathrm{Re}\phantom{\rule{0.2em}{0ex}}(E)\ensuremath{\leqslant}0$---well before the additional interaction is removed. Our study shows that realistic nucleon-nucleon interaction models exclude any possible experimental signature of three-neutron resonances.

Testing nonlocal nucleon-nucleon interactions in four-nucleon systems

The Faddeev-Yakubovski equations are solved in configuration space for the $% \alpha$-particle and n-$^3$H continuum states. We test the ability of nonlocal nucleon-nucleon interaction models to describe 3N and 4N systems.

High-precision proton-proton bremsstrahlung measurements at190MeV

Two high-accuracy measurements of cross sections and analyzing powers for the proton-proton bremsstrahlung reaction have been performed at $190\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}$ beam energy. These measurements provide not only the most accurate exclusive cross-section and analyzing-power data to date, but also a wide phase-space coverage. Thus, an accurate test of nucleon-nucleon interaction models is made feasible. The experimental setup and the analysis procedure are discussed in detail. Microscopic calculations and calculations based on the soft-photon theorem show deficiencies in explaining the bulk of the data.

Counter terms for low momentum nucleon–nucleon interactions

There is much current interest in treating low energy nuclear physics using the renormalization group (RG) and effective field theory (EFT). Inspired by this RG-EFT approach, we study a low-momentum nucleon–nucleon (NN) interaction, V low- k , obtained by integrating out the fast modes down to the scale Λ∼2 fm −1. Since NN experiments can only determine the effective interaction in this low momentum region, our chief purpose is to find such an interaction for complex nuclei whose typical momenta lie below this scale. In this paper we find that V low- k can be highly satisfactorily accounted for by the counter terms corresponding to a short range effective interaction. The coefficients C n of the power series expansion ∑ C n q n for the counter terms have been accurately determined, and results derived from several meson-exchange NN interaction models are compared. The counter terms are found to be important only for the S, P and D partial waves. Scaling behavior of the counter terms is studied. Finally we discuss the use of these methods for computing shell model matrix elements.

Correlation between the properties of the deuteron and the low-energy triplet parameters of neutron-proton scattering

The correlation relationship between the deuteron asymptotic normalization constant, $A_{S}$, and the triplet np scattering length, $a_{t}$, is investigated. It is found that 99.7% of the asymptotic constant $A_{S}$ is determined by the scattering length $a_{t}$. It is shown that the linear correlation relationship between the quantities $A_{S}^{-2}$ and $1/a_{t}$ provides a good test of correctness of various models of nucleon-nucleon interaction. It is revealed that, for the normalization constant $A_{S}$ and for the root-mean-square deuteron radius $r_{d}$, the results obtained with the experimental value recommended at present for the triplet scattering length $a_{t}$ are exaggerated with respect to their experimental counterparts. By using the latest experimental phase shifts of Arndt et al., we obtain, for the low-energy scattering parameters ($a_{t}$, $r_{t}$, $P_{t}$) and for the deuteron characteristics ($A_{S}$, $r_{d}$), results that comply well with experimental data.

Triton binding energy calculated from theSU6quark-model nucleon-nucleon interaction

Properties of the three-nucleon bound state are examined in the Faddeev formalism, in which the quark-model nucleon-nucleon interaction is explicitly incorporated to calculate the off-shell T matrix. The most recent version, fss2, of the Kyoto-Niigata quark-model potential yields the ground-state energy ${E(}^{3}\mathrm{H})=\ensuremath{-}8.514 \mathrm{MeV}$ in the 34 channel calculation, when the $\mathrm{np}$ interaction is used for the nucleon-nucleon interaction. The charge root mean square radii of the ${}^{3}\mathrm{H}$ and ${}^{3}\mathrm{He}$ are 1.72 fm and 1.90 fm, respectively, including the finite size correction of the nucleons. These values are the closest to the experiments among many results obtained by detailed Faddeev calculations employing modern realistic nucleon-nucleon interaction models.