In this paper, we study the relativistic effects in a three-body bound state. For this purpose, the relativistic form of the Faddeev equations is solved in momentum space as a function of the Jacobi momentum vectors without using a partial wave decomposition. The inputs for the three-dimensional Faddeev integral equation are the off-shell boost two-body $t-$matrices, which are calculated directly from the boost two-body interactions by solving the Lippmann-Schwinger equation. The matrix elements of the boost interactions are obtained from the nonrelativistic interactions by solving a nonlinear integral equation using an iterative scheme. The relativistic effects on three-body binding energy are calculated for the Malfliet-Tjon potential. Our calculations show that the relativistic effects lead to a roughly 2\% reduction in the three-body binding energy. The contribution of different Faddeev components in the normalization of the relativistic three-body wave function is studied in detail. The accuracy of our numerical solutions is tested by calculation of the expectation value of the three-body mass operator, which shows an excellent agreement with the relativistic energy eigenvalue.
Relativistic Faddeev equations for three-body scattering at arbitrary energies are solved in first order in the two-body transition operator in terms of momentum vectors without employing a partial wave decomposition. Relativistic invariance is incorporated within the framework of Poincar{é} invariant quantum mechanics. Based on a Malfliet-Tjon type interaction, observables for elastic and breakup scattering are calculated and compared to the nonrelativistic ones.
The Faddeev equations for the three-body bound state are solved directly as thre e-dimensional integral equations without employing partial wave decomposition. Two-body forces of the Malfliet-Tjon type and simple spin independent genuine three-body forces are considered for the calculation of the three-body binding energy.
The Complex Energy Method [Prog. Theor. Phys. {\bf 109}, 869L (2003)] is applied to the 4-body Faddeev-Yakubovsky equations in the 4-nucleon system. We obtain a well converged solution in all energy regions below and above the 4-nucleon break-up threshold.
The paper is devoted to the $\bar{K}NNN$ system, consisting of an antikaon and three nucleons. Four-body Faddeev-type AGS equations are being solved in order to find possible quasi-bound state in the system.
The paper is devoted to the $\bar{K}NNN$ system, which is an exotic system consisting of an antikaon and three nucleons. Four-body Faddeev-type AGS equations, which are being used for evaluation of the possible quasi-bound state in the system are described.
We propose a novel approach to solve the three-nucleon (3N) Faddeev equation which avoids the complicated singularity pattern going with the moving logarithmic singularities of the standard approach. In this new approach the treatment of the 3N Faddeev equation becomes essentially as simple as the treatment of the two-body Lippmann-Schwinger equation. Very good agreement of the new and old approaches in the application to nucleon-deuteron elastic scattering and the breakup reaction is found.
We present a practical method to solve Faddeev three-body equations at energies above three-body breakup threshold as integral equations in coordinate space. This is an extension of previously used method for bound states and scattering states below three-body breakup threshold energy. We show that breakup components in three-body reactions produce long-range effects on Faddeev integral kernels in coordinate space, and propose numerical procedures to treat these effects. Using these techniques, we solve Faddeev equations for neutron-deuteron scattering to compare with benchmark solutions.
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.
The halo nucleus $^{11}$Li is treated as a three-body system consisting of an inert core of $^{9}$Li plus two valence neutrons. The Faddeev equations are solved using separable potentials to describe the two-body interactions, corresponding in the n-$^{9}$Li subsystem to a p$_{1/2}$ resonance plus a virtual s-wave state. The experimental $^{11}$Li energy is taken as input and the $^{9}$Li transverse momentum distribution in $^{11}$Li is studied.
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.
The equations which relate three-body and two-body symmetry violating scattering amplitudes are derived in the first order of symmetry violating interactions. They can be used to obtain three-body symmetry violating scattering amplitudes from two-body symmetry violating scattering amplitudes calculated in low energy effective field theory.
A novel approach to solve the Faddeev equation for three-body scattering at arbitrary energies is proposed. This approach disentangles the complicated singularity structure of the free three-nucleon propagator leading to the moving and logarithmic singularities in standard treatments. The Faddeev equation is formulated in momentum space and directly solved in terms of momentum vectors without employing a partial wave decomposition. In its simplest form the Faddeev equation for identical bosons, which we are using, is an integral equation in five variables, magnitudes of relative momenta and an…
We discuss the appearance of spurious solutions of few-body equations for Faddeev amplitudes. The identification of spurious states, i.e., states that lack the symmetry required for solutions of the Schroedinger equation, as well as the symmetrization of the Faddeev equations is investigated. As an example, systems of three and four electrons, bound in a harmonic-oscillator potential and interacting by the Coulomb potential, are presented.
We study the nucleon solution of the relativistic Faddeev equation as a function of density in the framework of a generalized Nambu-Jona-Lasinio model. We truncate the interacting two-body channels to the scalar diquark channel, the coupling constant of which is treated as a parameter. A 3-momentum cut-off is used to regularize the model. The Faddeev equation is solved numerically using the methods developed by Tjon and others. At zero density the nucleon is bound only for unrealistically large values of the scalar coupling and this binding energy decreases quickly with increasing density.
The set of Faddeev and Lippmann--Schwinger integral equations for three-body systems involving Coulomb interactions deduced from a ``three-potential'' picture are shown to be compact for all energies and a method of solution is given.
A novel approach is developed to find the three-body breakup amplitudes and cross sections within the modified Faddeev equation framework. The method is based on the lattice-like discretization of the three-body continuum with a three-body stationary wave-packet basis in momentum space. The approach makes it possible to simplify drastically all the three- and few-body breakup calculations due to discrete wave-packet representations for the few-body continuum and simultaneous lattice representation for all the scattering operators entering the integral equation kernels. As a result, the few-bod…
FaCE is a self contained programme, with namelist input, that solves the three body Faddeev equations. It enables the inclusion of excitation of one of the three bodies, whilst the other two remain inert. It is particularly useful for obtaining the binding energies and bound state structure compositions of light exotic nuclei treated as three-body systems, given the three effective two body interactions. A large variety of forms for these interactions may be defined, and supersymmetric transformations of these potentials may be calculated whenever two body states need to be removed due to Paul…
The diquark and nucleon are studied in a non-local NJL model. We solve the relativistic Faddeev equation and compare the results with the ordinary NJL model. Although the model is quark confining, it is not diquark confining in the rainbow-ladder approximation. We show that the off-shell contribution to the diquark $T$ matrix is crucial for the structure of the nucleon: without its inclusion the attraction in the scalar channel is too weak to form a three-body bound state.
Algorithm, based on explicit representations for analytic continuation of the T-matrix Faddeev components on unphysical sheets, is worked out for calculations of resonances in the three-body quantum problem. According to the representations, poles of T-matrix, scattering matrix and Green function on unphysical sheets, interpreted as resonances, coincide with those complex energy values where appropriate truncations of the scattering matrix have zero as eigenvalue. Scattering amplitudes on the physical sheet, necessary to construct scattering matrix, are calculated on the basis of the Faddeev d…
We demonstrate the feasibility and efficiency of the Coulomb-Sturmian separable expansion method for generating accurate solutions of the Faddeev equations. Results obtained with this method are reported for several benchmark cases of bosonic and fermionic three-body systems. Correct bound-state results in agreement with the ones established in the literature are achieved for short-range interactions. We outline the formalism for the treatment of three-body Coulomb systems and present a bound-state calculation for a three-boson system interacting via Coulomb plus short-range forces. The corres…
We extend our formulation of relativistic three-nucleon Faddeev equations to include both pairwise interactions and a three-nucleon force. Exact Poincare invariance is realized by adding interactions to the mass Casimir operator (rest Hamiltonian) of the non-interacting system without changing the spin Casimir operator. This is achieved by using interactions defined by rotationally invariant kernels that are functions of internal momentum variables and single-particle spins that undergo identical Wigner rotations. To solve the resulting equations one needs matrix elements of the three-nucleon …
A novel method for calculating resonances in three-body Coulombic systems is presented. The Faddeev-Merkuriev integral equations are solved by applying the Coulomb-Sturmian separable expansion method. To show the power of the method we calculate resonances of the three-$α$ and the $H^-$ systems.
The polarization transfer coefficient $K_y^{y'}$ for the $^2$H$(\vec{d}, \vec{p})^3$H reaction at energies $E_{\rm lab.} = 30$, 50, 70, and 90keV is calculated using the four-body Faddeev-Yakubovsky equation. We employ a separable type of the Paris potential. The experimental data [Phys. Rev. {\bf C64}, 047601 (2001)] agrees with our solution at the scattering angle $θ_{\rm c.m.}=0^\circ$, and there is no discrepancy pointed out in that paper. We found that the $K_y^{y'}$ is sensitive to the incident deuteron energy at this angle.
Algorithm, based on explicit representations for analytic continuation of the T-matrix Faddeev components on unphysical sheets, is worked out for calculations of resonances in the three-body quantum problem. According to the representations, poles of the T--matrix, scattering matrix and resolvent on unphysical sheets, interpreted as resonances, coincide with those complex energy values where appropriate truncations of the scattering matrix have zero as eigenvalue. Scattering amplitudes on the physical sheet, necessary to construct scattering matrix, are calculated on the basis of the Faddeev d…
A detailed comparison of Faddeev and variational wave functions for $^3$H, calculated with realistic nuclear forces, has been made to study the form of three-body correlations in few-body nuclei. Three new three-body correlations for use in variational wave functions have been identified, which substantially reduce the difference with the Faddeev wave function. The difference between the variational upper bound and the Faddeev binding energy is reduced by half, to typically $<2\%$. These three-body correlations also produce a significant lowering of the variational binding energy for $^4$He an…
Four-body Faddeev-Yakubovsky calculations for Lambda-Lambda-p-n do not produce a bound state for Lambda-Lambda hydrogen 4, although suitably defined three-body Faddeev calculations for Lambda-Lambda-d produce a 1+ bound state for Lambda-Lambda interactions fitted to the Lambda-Lambda helium 6 emulsion event from KEK E373. This is opposite to the normal situation where a four-body Faddeev-Yakubovsky calculation yields stronger binding than that due to a suitably defined three-body Faddeev calculation. For stranger systems, Faddeev calculations using Lambda-Xi interactions which simulate the Nij…
We solve the Faddeev equations for the two meson-one baryon system $ππN$ and coupled channels using the experimental two-body $t$-matrices for the $πN$ interaction as input and unitary chiral dynamics to describe the interaction between the rest of coupled channels. In addition to the $N^*(1710)$ obtained before with the $ππN$ channel, we obtain, for $J^π=1/2^+$ and total isospin of the three-body system $I=1/2$, a resonance peak whose mass is around 2080 MeV and width of 54 MeV, while for $I=3/2$ we find a peak around 2126 MeV and 42 MeV of width. These two resonances can be identified with t…
Given the phenomenological success of the Nambu-Jona-Lasinio model in describing the meson physics in the low energy limit, it is tempting to find the fully relativistically structured nucleon solution in the same model under the similar approximation employed in the mesonic sector. To achieve this goal we need to solve a relativistic Faddeev equation. The factorizability of the two-body T-matrix reduces the three-body Faddeev equation to a tractable two-body Bethe-Salpeter equation. The reduced equation is then solved numerically. Our result indicates that the nucleon consists of three loosel…
The influence of the partial-wave states with nonzero orbital moment of the nucleon pair on the binding energy of the triton in the relativistic case is considered. The relativistic generalization of the Faddeev equation in the Bethe-Salpeter formalism is applied. Two-nucleon t matrix is obtained from the Bethe-Salpeter equation with separable kernel of nucleon-nucleon interaction of the rank one. The kernel form factors are the relativistic type of the Yamaguchi functions. The following two-nucleon partial-wave states are considered: $^1S_0$, $^3S_1$, $^3D_1$, $^3P_0$, $^1P_1$, $^3P_1$. The s…
Low-energy muon-transfer cross sections and rates in collisions of muonic atoms with hydrogen isotopes are calculated using a six-state close-coupling approximation to coordinate-space Faddeev-Hahn-type equations. In the muonic case satisfactory results are obtained for all hydrogen isotopes and the experimentaly observed strong isotopic dependence of transfer rates is also reproduced. A comparison with results of other theoretical and available experimental works is presented. The present model also leads to good transfer cross sections in the well-understood problem of antihydrogen formation…
Evidence for particle stability of Lambda-Lambda hydrogen-4 (4LLH) has been suggested by the BNL-AGS E906 experiment. We report on Faddeev-Yakubovsky calculations for the four-body Lambda-Lambda-p-n system using Lambda-N interactions which reproduce the observed binding energy of Lambda hydrogen-3 (3LH) within a Faddeev calculation for the Lambda-p-n subsystem. No 4LLH bound state is found over a wide range of Lambda-Lambda interaction strengths, although the Faddeev equations for a three-body Lambda-Lambda-d model of 4LLH admit a 1+ bound state for as weak a Lambda-Lambda interaction strength…
A relativistic Faddeev model for the baryon octet is extended to treat the baryon decuplet. We find that after determining the model parameters in the mesonic sector the masses of both nucleon and delta deviate by less than 5\% from the experimental data and show only a very weak dependence on the constituent quark mass.
\noindent{\bf Background:} Deuteron-induced nuclear reactions are an essential tool for probing the structure of nuclei as well as astrophysical information such as $(n,γ)$ cross sections. The deuteron-nucleus system is typically described within a Faddeev three-body model consisting of a neutron ($n$), a proton ($p$), and the target nucleus ($A$) interacting through pairwise phenomenological potentials. While Faddeev techniques enable the exact description of the three-body dynamics, their predictive power is limited in part by the omission of irreducible neutron-proton-nucleus three-body for…
The formal scattering theory is developed for the three-particle differential Faddeev equations. The theory is realised along the same line as in the standard two-body case. The solution of the scattering problem is expressed in terms of the matrix T-operator constructed from the matrix resolvent of the differential Faddeev equations. The relationships of the matrix T-operator with elements of transition operators and Faddeev T-matrix components have been established.
We implement complex scaling of Faddeev equations using hyper-spheric coordinates and adiabatic expansion. Complex scaling of coordinates allows convenient calculations of three-body resonances. We derive the necessary equations and investigate the adiabatic spectrum at large distances. We illustrate the viability of the implementation by calculations of several three-body resonances: a $0^+$ resonance in a model benchmark system of three identical bosons; the $2^+$ resonance in the $^6$He nucleus within the $α+n+n$ model; and the two $0^+$ resonances in $^{12}$C within the three-$α$ model.
A recently developed three-dimensional approach (without partial-wave decomposition) is considered to investigate solutions of Faddeev-Yakubovsky integral equations in momentum space for three- and four-body bound states, with the inclusion of three-body forces. In the calculations of the binding energies, spin-dependent nucleon-nucleon (NN) potential models (named, S$_{3}$, MT-I/III, YS-type and P$_{5.5}$GL) are considered along with the scalar two-meson exchange three-body potential. Good agreement of the presently reported results with the ones obtained by other techniques are obtained, dem…
Three-body Faddeev equations are considered as a spectral problem for nonsymmetrical matrix operator. Invariant subspaces related to physical and spurious solutions to Faddeev equations and its adjoint are described. Respective eigenvectors corresponding to invariant subspaces are constructed for Faddeev operator and its adjoint. Extensions of the formalism on CCA equations are discussed.
Obtaining cross sections for nuclear reactions at intermediate energies based on the Glauber formulation has a long tradition. Only recently the energy regime of a few hundred MeV has become accessible to ab-initio Faddeev calculations of three-body scattering. In order to go to higher energies, the Faddeev equation for three-body scattering is formulated and directly solved without employing a partial wave decomposition. In the simplest form the Faddeev equation for interacting scalar particles is a three-dimensional integral equation in five variables, from which the total cross section, the…
Using separable $\bar{K}N-πΣ$ potentials in the Faddeev equations, we calculated the binding energies and widths of the $K^{-}pp$, $K^{-}ppn$ and $K^{-}ppp$ quasi-bound states on the basis of three- and four-body Alt-Grassberger-Sandhas equations in the momentum representation. One- and two-pole version of $\bar{K}N-πΣ$ interaction are considered and the dependence of the resulting few-body energy on the two-body $\bar{K}N-πΣ$ potential was investigated. The $s$-wave [3+1] and [2+2] sub-amplitudes are obtained by using the Hilbert-Schmidt expansion procedure for the integral kernels. As a resu…
A partial-wave decomposition of the Faddeev amplitude of a Poincare-invariant three-fermion bound state is presented. Some implications for the properties of the nucleon as relativistic three-quark bound state are discussed. E.g. it is demonstrated that the nucleon is not spherically symmetric.
The core excitation, being an important reaction mechanism, so far is not properly included in most calculations of three-body nuclear reactions. We aim to include the excitation of the core nucleus using an exact Faddeev-type framework for nuclear reactions in the three-body (core + neutron + proton) system. We employ Alt, Grassberger, and Sandhas (AGS) integral equations for the three-particle transition operators and solve them in the momentum-space framework. The Coulomb interaction is included via the method of screening and renormalization. We calculate elastic, inelastic, and transfer r…
A method is presented that allows to solve the Faddeev integral equations of the semirelativistic constituent quark model. In such a model the quark-quark interaction is modeled by a infinitely rising confining potential and the kinetic energy is taken in a relativistic form. We solve the integral equations in Coulomb-Sturmian basis. This basis facilitate an exact treatment of the confining potentials.
The first ever numerical solution of five-body Faddeev-Yakubovsky equations is presented in this work. Modern realistic Nucleon-Nucleon Hamiltonians have been tested when describing low energy elastic neutron scattering on $^4$He nucleus. Obtained results have been compared with those available in the literature and based on solution of the Schrödinger equation.
Exact Faddeev-type three-body equations are applied to the study of the proton transfer reactions $(d,n)$ in the system consisting of a nuclear core and two nucleons. The integral equations for the three-body transition operators are solved in the momentum-space framework including the Coulomb interaction via the screening and renormalization method. For a weakly bound final nucleus the calculation of the $(d,n)$ reaction is more demanding in terms of the screening radius as compared to the $(d,p)$ reaction. Well converged differential cross section results are obtained for $^{7}{Be}(d,n)^{8}{…
By solving the Faddeev equations we calculate the mass of the strange baryons in the framework of a relativistic constituent quark model. The Goldstone-boson-exchange quark-quark interaction is derived from $SU(3)_F$ symmetry, which is explicitly broken as the strange quark is much heavier. This broken symmetry can nicely be accounted for in the Faddeev framework.
We use equations for Faddeev amplitudes to solve the shell-model problem for four nucleons in the model space that includes up to 14 hbar Omega harmonic-oscillator excitations above the unperturbed ground state. Two- and three-body effective interactions derived from the Reid93 and Argonne V8' nucleon-nucleon potentials are used in the calculations. Binding energies, excitations energies, point-nucleon radii and electromagnetic and strangeness charge form factors for 4He are studied. The structure of the Faddeev-like equations is discussed and a formula for matrix elements of the permutation o…
Coupled-channel three-body calculations of an $I=1/2$, $J^π=0^-$ $\bar{K}NN$ quasi-bound state in the $\bar{K}NN - πΣN$ system were performed and the dependence of the resulting three-body energy on the two-body $\bar{K}N - πΣ$ interaction was investigated. Earlier results of binding energy $B_{K^-pp} \sim 50 -70$ MeV and width $Γ_{K^-pp} \sim 100$ MeV are confirmed [N.V. Shevchenko {\it et al.}, Phys. Rev. Lett. {\bf 98}, 082301 (2007)]. It is shown that a suitably constructed energy-independent complex $\bar{K}N$ potential gives a considerably shallower and narrower three-body quasi-bound st…
We propose a method that allows for the efficient solution of the three-body Faddeev equations in the presence of infinitely rising confinement interactions. Such a method is useful in calculations of nonrelativistic and especially semirelativistic constituent quark models. The convergence of the partial wave series is accelerated and possible spurious contributions in the Faddeev components are avoided. We demonstrate how the method works with the example of the Goldstone-boson-exchange chiral quark model for baryons.
The work is devoted to comparison of two different approaches to calculation of three-body resonances on the basis of the Faddeev differential equations. The first one is the well known complex scaling approach. The second method is based on an immediate calculation of the zeros of the scattering matrix continued to the physical sheet.
A modified version of the Faddeev three-body equation to accommodate the Coulomb interaction, which was used in the study of three-nucleon bound states, is applied to the proton-deuteron scattering problem at energies below the three-body breakup threshold. A formal derivation of the equation in a time-independent scattering theory is given. Numerical results for phase shift parameters are presented to be compared with those of another methods and results of the phase shift analysis. Differential cross sections and nucleon analyzing powers are calculated with the effects of three-nucleon force…
In this paper, I prove that the sub-Coulomb $A(d,p)B$ reaction amplitude, which is a solution of the three-body Faddeev equations in the Alt-Grassberger-Sandhas (AGS) form, is peripheral if a peripheral is the corresponding DWBA amplitude. Hence the Faddeev's reaction amplitude for the sub-Coulomb $A(d,p)B$ reactions can also be parametrized in terms of the ANC of the $(n\,A)$ bound state. First, I consider the original AGS equations with separable potentials and prove that such equations are peripheral at sub-Coulomb energies. After that, the two-particle AGS equations are derived for the gen…
Background: The numerical solution of few-body scattering problems with realistic interactions is a difficult problem that normally must be solved on powerful supercomputers, taking a lot of computer time. This strongly limits the possibility of accurate treatments for many important few-particle problems in different branches of quantum physics. Purpose: To develop a new general highly effective approach for the practical solution of few-body scattering equations that can be implemented on a graphics processing unit. Methods: The general approach is realized in three steps: (i) the reformulat…
A chirally-motivated coupled-channel $\bar{K}N$ potential, reproducing all low-energy experimental data on $K^- p$ scattering and kaonic hydrogen and suitable for using in accurate few-body calculations, was constructed. The potential was used for calculations of low-energy amplitudes of the elastic $K^- d$ scattering using Faddeev-type AGS equations with coupled $\bar{K}NN$ and $πΣN$ channels. A complex $K^- - d$ potential reproducing the three-body $K^- d$ amplitudes was constructed and used for calculation of $1s$ level shift and width of kaonic deuterium. The predicted shift $ΔE_{1s}^{K^- …
The scattering length for the eta-meson collision with deuteron is calculated on the basis of rigorous few-body equations (AGS) for various eta-N input. The results obtained strongly support the existence of a resonance or quasi-bound state close to the eta-d threshold.
Effective lambda-proton and lambda-neutron potentials, restored from theoretical scattering phases through Gel'fand-Levitan-Marchenko theory, are tested on a lambda hypertriton through three-body calculations. The lambda hypertriton is treated as a three-body system consisting of lambda-proton, lambda-neutron and proton-neutron subsystems. Binding energy and root-mean-square radius are computed for the ground state of lambda hypertriton ($J^π=1/2^+$). In coordinate space, the dynamics of the system is described using a set of coupled hyperradial equations obtained from the Differential Faddeev…
We have introduced a spin-isospin dependent three-dimensional approach for formulation of the three-nucleon scattering. Faddeev equation is expressed in terms of vector Jacobi momenta and spin-isospin quantum numbers of each nucleon. Our formalism is based on connecting the transition amplitude $T$ to momentum-helicity representations of the two-body $t$-matrix and the deuteron wave function. Finally the expressions for nucleon-deuteron elastic scattering and full breakup process amplitudes are presented.
