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Z. Papp

Publications and source records attributed to Z. Papp.

At least 37 records · Page 2Linked to original sources
arXiv2004

$e^+ + H$ direct annihilation above the positronium formation threshold

A long-standing problem with the solution of the Schrödinger equation has been its inability to account for the electron-positron annihilation in positron hydrogen scattering above the positronium formation threshold. This letter shows that this problem has been resolved by the use of the modified Faddeev equations. A number of $e^- e^+$ annihilation cross sections in the energy gap between $Ps(1s)$ and $H(n=2)$ thresholds are reported for both the positron plus hydrogen incoming channel as well as the proton plus positronium incoming channel. However the indirect annihilation cross sections after formation of the positronium themselves are well known, they will not be included in this report.

physics.atm-clus↗
arXiv2004

Accumulation of three-body resonances above two-body thresholds

We calculate resonances in three-body systems with attractive Coulomb potentials by solving the homogeneous Faddeev-Merkuriev integral equations for complex energies. The equations are solved by using the Coulomb-Sturmian separable expansion approach. This approach provides an exact treatment of the threshold behavior of the three-body Coulombic systems. We considered the negative positronium ion and, besides locating all the previously know $S$-wave resonances, we found a whole bunch of new resonances accumulated just slightly above the two-body thresholds. The way they accumulate indicates that probably there are infinitely many resonances just above the two-body thresholds, and this might be a general property of three-body systems with attractive Coulomb potentials.

physics.atom-ph↗
arXiv2003

Three-body confinement force in a realistic constituent quark model

We show that in realistic constituent quark models based on a two-body confinement interaction color states appear in the middle of the experimentally known spectrum. To avoid this situation we implement a three-body confinement interaction, introduced on an algebraic basis, into a semirelativistic version of the Goldstone-boson-exchange constituent quark model and by solving the Faddeev equations we show that this interaction can increase the gap between singlet and colour states, such as the latter can be ignored and the known baryons can be described as $q^3$ systems. We analyze the effect of a $Δ$- and a Y-shape three-body interaction.

hep-ph↗
arXiv2002

Faddeev-Merkuriev equations for resonances in three-body Coulombic systems

We reconsider the homogeneous Faddeev-Merkuriev integral equations for three-body Coulombic systems with attractive Coulomb interactions and point out that the resonant solutions are contaminated with spurious resonances. The spurious solutions are related to the splitting of the attractive Coulomb potential into short- and long-range parts, which is inherent in the approach, but arbitrary to some extent. By varying the parameters of the splitting the spurious solutions can easily be ruled out. We solve the integral equations by using the Coulomb-Sturmian separable expansion approach. This solution method provides an exact description of the threshold phenomena. We have found several new S-wave resonances in the e- e+ e- system in the vicinity of thresholds.

physics.atom-ph↗
arXiv2001

Multichannel $e^{\pm}$ scattering on excited Ps states

Scattering and reaction cross sections of $e^{\pm}-Ps$ system are calculated for total angular momentum L=0, 1 and 2 and energies between the Ps(n=2)-Ps(n=3) threshold. We solved a set of Faddeev-Merkuriev and Lippmann-Schwinger integral equations by applying the Coulomb-Sturmian separable expansion technique. We found that the excited positronium states play dominating roles in scattering processes.

physics.atom-ph↗
arXiv2001

Three-potential formalism for the three-body scattering problem with attractive Coulomb interactions

A three-body scattering process in the presence of Coulomb interaction can be decomposed formally into a two-body single channel, a two-body multichannel and a genuine three-body scattering. The corresponding integral equations are coupled Lippmann-Schwinger and Faddeev-Merkuriev integral equations. We solve them by applying the Coulomb-Sturmian separable expansion method. We present elastic scattering and reaction cross sections of the $e^++H$ system both below and above the $H(n=2)$ threshold. We found excellent agreements with previous calculations in most cases.

physics.atom-ph↗
arXiv2001

On the Coulomb Sturmian matrix elements of relativistic Coulomb Green's operators

The Hamiltonian of the radial Coulomb Klein-Gordon and second order Dirac equations are shown to possess an infinite symmetric tridiagonal matrix structure on the relativistic Coulomb Sturmian basis. This allows us to give an analytic representation for the corresponding Coulomb Green's operators in terms of continued fractions. The poles of the Green's matrix reproduce the exact relativistic hydrogen spectrum.

quant-ph↗
arXiv2000

Faddeev approach to confined three-quark problems

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.

nucl-th↗
arXiv1999

Continued fraction representation of the Coulomb Green's operator and unified description of bound, resonant and scattering states

If a quantum mechanical Hamiltonian has an infinite symmetric tridiagonal (Jacobi) matrix form in some discrete Hilbert-space basis representation, then its Green's operator can be constructed in terms of a continued fraction. As an illustrative example we discuss the Coulomb Green's operator in Coulomb-Sturmian basis representation. Based on this representation, a quantum mechanical approximation method for solving Lippmann-Schwinger integral equations can be established, which is equally applicable for bound-, resonant- and scattering-state problems with free and Coulombic asymptotics as well. The performance of this technique is illustrated with a detailed investigation of a nuclear potential describing the interaction of two $α$ particles.

nucl-th↗
arXiv1999

Integral equations for three-body Coulombic resonances

We propose a novel method for calculating resonances in three-body Coulombic systems. The method is based on the solution of the set of Faddeev and Lippmann-Schwinger integral equations, which are designed for solving the three-body Coulomb problem. The resonances of the three-body system are defined as the complex-energy solutions of the homogeneous Faddeev integral equations. We show how the kernels of the integral equations should be continued analytically in order that we get resonances. As a numerical illustration a toy model for the three-$α$ system is solved.

nucl-th↗
arXiv1999

The three-body Coulomb scattering problem in discrete Hilbert-space basis representation

For solving the $2\to 2,3$ three-body Coulomb scattering problem the Faddeev-Merkuriev integral equations in discrete Hilbert-space basis representation are considered. It is shown that as far as scattering amplitudes are considered the error caused by truncating the basis can be made arbitrarily small. By this truncation also the Coulomb Green's operator is confined onto the two-body sector of the three-body configuration space and in leading order can be constructed with the help of convolution integrals of two-body Green's operators. For performing the convolution integral an integration contour is proposed that is valid for all energies, including bound-state as well as scattering energies below and above the three-body breakup threshold.

nucl-th↗
arXiv1998

On the treatment of confinement in three-quark calculations

The treatment of confining interactions in non-relativistic three-quark systems is revised. Usually in the Faddeev equations the Faddeev components are coupled by the total potential. In the new treatment the Faddeev components are coupled only by the non-confining short-range part of the potential, allowing thus its channel-by-channel investigation. The convergence in angular momentum channels is much faster.

hep-ph↗
arXiv1998

Unified treatment of the Coulomb and harmonic oscillator potentials in $D$ dimensions

Quantum mechanical models and practical calculations often rely on some exactly solvable models like the Coulomb and the harmonic oscillator potentials. The $D$ dimensional generalized Coulomb potential contains these potentials as limiting cases, thus it establishes a continuous link between the Coulomb and harmonic oscillator potentials in various dimensions. We present results which are necessary for the utilization of this potential as a model and practical reference problem for quantum mechanical calculations. We define a Hilbert space basis, the generalized Coulomb-Sturmian basis, and calculate the Green's operator on this basis and also present an SU(1,1) algebra associated with it. We formulate the problem for the one-dimensional case too, and point out that the complications arising due to the singularity of the one-dimensional Coulomb problem can be avoided with the use of the generalized Coulomb potential.

quant-ph↗