arXiv subjects

W. Gloeckle

Publications and source records attributed to W. Gloeckle.

At least 37 records · Page 2Linked to original sources

arXiv2008

Poincaré Invariant Three-Body Scattering at Intermediate Energies

The relativistic Faddeev equation for three-nucleon scattering is formulated in momentum space and directly solved in terms of momentum vectors without employing a partial wave decomposition. The equation is solved through Padé summation, and the numerical feasibility and stability of the solution is demonstrated. Relativistic invariance is achieved by constructing a dynamical unitary representation of the Poincaré group on the three-nucleon Hilbert space. Based on a Malfliet-Tjon type interaction, observables for elastic and break-up scattering are calculated for projectile energies in the intermediate energy range up to 2 GeV, and compared to their nonrelativistic counterparts. The convergence of the multiple scattering series is investigated as a function of the projectile energy in different scattering observables and configurations. Approximations to the two-body interaction embedded in the three-particle space are compared to the exact treatment.

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arXiv2007

Relativistic Effects in Exclusive pd Breakup Scattering at Intermediate Energies

The relativistic Faddeev equation for three-nucleon scattering is formulated in momentum space and directly solved in terms of momentum vectors without employing a partial wave decomposition. Relativistic invariance is achieved by constructing a dynamical unitary representation of the Poincaré group on the three-nucleon Hilbert space. The exclusive breakup reaction at 508 MeV is calculated based on a Malfliet-Tjon type of two-body interaction and the cross sections are compared to measured cross sections at this energy. We find that the magnitude of the relativistic effects can be quite large and depends on the configurations considered. In spite of the simple nature of the model interaction, the experimental cross sections are in surprisingly good agreement with the predictions of the relativistic calculations. We also find that although for specific configurations the multiple scattering series converges rapidly, this is in general not the case.

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arXiv2007

Realistic two-nucleon potentials for the relativistic two-nucleon Schroedinger equation

The potentials $V (v)$ in the nonrelativistic (relativistic) nucleon-nucleon (NN) Schroedingerequation are related by a quadratic equation. That equation is numerically solved, thus providing phase equivalent v- potentials related for instance to the high precision NN potentials, which are adjusted to NN phase shift and mixing parameters in a nonrelativistic Schroedinger equation. The relativistic NN potentials embedded in a three-nucleon (3N)system for total NN momenta different from zero are also constructed in a numerically precise manner. They enter into the relativistic interacting 3N mass operator, which is needed for relativistic 3N calculations for bound and scattering states.

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arXiv2007

Relativistic Three-Body Scattering in a First Order Faddeev Formulation

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.

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arXiv2007

Three-Nucleon Scattering at Intermediate Energies

By means of a technique, which does not employ partial wave (PW) decompositions, the nucleon-deuteron break-up process is evaluated in the Faddeev scheme, where only the leading order term of the amplitude is considered. This technique is then applied to calculate the semi-exclusive proton-deuteron break-up reaction d(p,n)pp for proton laboratory energies Elab of a few hundred MeV. A comparison with PW calculations is performed at 197 MeV projectile energy. At the same energy rescattering processes, which are not included in the 3D calculations yet, are shown to be still important in the full Faddeev PW calculations, especially for the cross section and the analyzing power Ay. Next, kinematical relativistic effects are investigated for projectile energies up to about 500 MeV. At the higher energies, those relativistic effects start not to be negligible, especially in the peak of the cross section.

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arXiv2007

First Order Relativistic Three-Body Scattering

Relativistic Faddeev equations for three-body scattering at arbitrary energies are formulated in momentum space and in first order in the two-body transition-operator directly solved in terms of momentum vectors without employing a partial wave decomposition. Relativistic invariance is incorporated within the framework of Poincare invariant quantum mechanics, and presented in some detail. Based on a Malfliet-Tjon type interaction, observables for elastic and break-up scattering are calculated up to projectile energies of 1 GeV. The influence of kinematic and dynamic relativistic effects on those observables is systematically studied. Approximations to the two-body interaction embedded in the three-particle space are compared to the exact treatment.

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arXiv2006

Three-Body Elastic and Inelastic Scattering at Intermediate Energies

The Faddeev equation for three-body scattering at arbitrary energies is formulated in momentum space and directly solved in terms of momentum vectors without employing a partial wave decomposition. For identical bosons this results in a three-dimensional integral equation in five variables, magnitudes of relative momenta and angles. The cross sections for both elastic and breakup processes in the intermediate energy range up to about 1 GeV are calculated based on a Malfliet-Tjon type potential, and the convergence of the multiple scattering series is investigated.

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arXiv2006

Polarization observables in exclusive kaon photoproduction on the deuteron

Single and double polarization observables for kaon photoproduction on the deuteron are studied theoretically with modern hyperon-nucleon forces. The kinematical region of the kaon scattered forward with large momentum is thoroughly investigated where either the quasifree scattering leading to the kaon and hyperon or the final-state interaction between hyperon and nucleon are expected. The quasifree scatterings show characteristic peaks in the inclusive cross sections. The final-state interaction effects are significant, especially around the Lambda-N and Sigma-N thresholds. The double polarization C_z is found to be sensitive to the final-state interaction effects. Precise data would help to clarify the property of the Lambda-N--Sigma-N interaction and also help to extract the information on the elementary amplitude from the quasifree scattering region.

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arXiv2006

K0 photoproduction on the deuteron and the extraction of the elementary amplitude

The photoproduction of K0 on the deuteron has been investigated with the inclusion of YN and KN final-state interaction (FSI), as well as the pion-mediated process gamma d --> pi NN --> KYN. The YN rescattering effects for the inclusive cross section are found to be large in the threshold regions. Polarization observables show sizable FSI effects at larger kaon and hyperon angles. It is shown that the extraction of the elementary gamma N --> KY amplitude is possible in the quasi-free scattering region where FSI effects are negligible. Furthermore, the cross sections in this region are large, indicating that measurements in this kinematical region are favored.

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arXiv2006

Nucleon-deuteron capture with chiral potentials

Present day chiral nucleon-nucleon potentials up to N3LO and three nucleon forces at N2LO are used to analyze nucleon-deuteron radiative capture at deuteron lab energies below E_d= 100 MeV. The differential cross section and the deuteron analyzing powers A_y(d) and A_{yy} are presented and compared to data. The theoretical predictions are obtained in the momentum-space Faddeev approach using the nuclear electromagnetic current operator with exchange currents introduced via the Siegert theorem. The chiral forces provide the same quality of data description as a combination of the two-nucleon AV18 and the three-nucleon Urbana IX interactions. However, the different parametrizations of the chiral potentials lead to broad bands of predictions.

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arXiv2006

A first estimation of chiral four-nucleon force effects in 4He

We estimate four-nucleon force effects between different 4He wave functions by calculating the expectation values of four-nucleon potentials which were recently derived within the framework of chiral effective field theory. We find that the four-nucleon force is attractive for the wave functions with a totally symmetric momentum part. The additional binding energy provided by the long-ranged part of the four-nucleon force is of the order of a few hundred keV.

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arXiv2006

Lorentz boosted nucleon-nucleon potential applied to the 3He(e,e'p)pn and 3He(e,e'n)pp processes

We formulate an approximate relativistic framework for an analysis of the 3He(e,e'p)pn and 3He(e,e'n)pp reactions with polarized electrons and 3He in the initial state. Restricting the rescattering series to one term linear in the two-nucleon t-matrix we incorporate various relativistic features when calculating a nuclear current matrix element. These relativistic ingredients encompass the relativistic 3He wave function based on the concept of the Lorentz boosted nucleon-nucleon potential together with the boosted 2N t-matrix, relativistic kinematics and relativistic single-nucleon current operator. This allows us to estimate the magnitude of relativistic effects not included in the standard nonrelativistic approach.

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arXiv2005

Three-atom scattering via the Faddeev scheme in configuration space

Faddeev equations in configuration space and integral form for three-atom scattering processes are formulated allowing for additive and nonadditive forces. The explicit partial wave decomposition is displayed. This formulation appears to be a valuable alternative to current approaches based on hyperspherical harmonic expansion methods of the Schrödinger equation.

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arXiv2005

Resolving the Discrepancy of 135 MeV pd Elastic Scattering Cross Sections and Relativistic Effects

Three precise measurements for elastic pd scattering at 135 MeV/A have been performed with the three different experimental setups. The cross sections are described well by the theoretical predictions based on modern nucleon-nucleon forces combined with three nucleon forces. Relativistic Faddeev calculations show that relativistic effects are restricted to backward angles. This result supports the two measurements recently reported by RIKEN and contradicts the KVI data.

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arXiv2005

Three-Body Scattering at Intermediate Energies

The Faddeev equation for three-body scattering at arbitrary energies 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 a three-dimensional integral equation in five variables, magnitudes of relative momenta and angles. This equation is solved through Pade summation. Based on a Malfliet-Tjon-type potential, the numerical feasibility and stability of the algorithm for solving the Faddeev equation is demonstrated. Special attention is given to the selection of independent variables and the treatment of three-body break-up singularities with a spline based method. The elastic differential cross section, semi-exclusive d(N,N') cross sections and total cross sections of both elastic and breakup processes in the intermediate energy range up to about 1 GeV are calculated and the convergence of the multiple scattering series is investigated in every case. In general a truncation in the first or second order in the two-body t-matrix is quite insufficient.

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arXiv2005

Measurement of the asymmetries in 3He(e,e'p)d and 3He(e,e'p)np

The electron-target-asymmetries A_parallel and A_perpendicular with target spin parallel and perpendicular to the momentum transfer q were measured for both the two-- and three-body breakup of 3He in the 3He(e,e'p)-reaction. Polarized electrons were scattered off polarized 3He in the quasielastic regime in parallel kinematics with the scattered electron and the knocked-out proton detected using the Three-Spectrometer-Facility at MAMI. The results are compared to Faddeev calculations which take into account Final State Interactions as well as Meson Exchange Currents. The experiment confirms the prediction of a large effect of Final State Interactions in the asymmetry of the three-body breakup and of an almost negligible one for the two-body breakup.

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arXiv2005

Systematic study of three-nucleon force effects in the cross section of the deuteron-proton breakup at 130 MeV

High precision cross-section data of the deuteron-proton breakup reaction at 130 MeV are presented for 72 kinematically complete configurations. The data cover a large region of the available phase space, divided into a systematic grid of kinematical variables. They are compared with theoretical predictions, in which the full dynamics of the three-nucleon (3N) system is obtained in three different ways: realistic nucleon-nucleon (NN) potentials are combined with model 3N forces (3NF's) or with an effective 3NF resulting from explicit treatment of the Delta-isobar excitation. Alternatively, the chiral perturbation theory approach is used at the next-to-next-to-leading order with all relevant NN and 3N contributions taken into account. The generated dynamics is then applied to calculate cross-section values by rigorous solution of the 3N Faddeev equations. The comparison of the calculated cross sections with the experimental data shows a clear prefernce for the predictions in which the 3NF's are included. The majority of the experimental data points is well reproduced by the theoretical predictions. The remaining discrepancies are investigated by inspecting cross sections integrated over certain kinematical variables. The procedure of global comparisons leads to establishing regularities in disagreements between the experimental data and the theoretically predicted values of the cross sections. They indicate deficiencies still present in the assumed models of the 3N system dynamics.

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arXiv2005

Proton polarizations in polarized 3He studied with the \vec{3He} (\vec{e},e' p)d and \vec{3He} (\vec{e},e' p)pn processes

We study within the Faddeev framework the \vec{3He} (\vec{e},e' p)d as well as the \vec{3He} (\vec{e},e' p)pn and \vec{3He} (\vec{e},e' n)pp reactions in order to extract information on the proton and neutron polarization in polarized 3He. We achieve clear analytical insight for simplified dynamical assumptions and define conditions for experimental access to important 3He properties. In addition we point to the possibility to measure the electromagnetic proton form factors in the process \vec{3He} (\vec{e},e' p)d which would test the dynamical picture and put limits on medium corrections of the form factors.

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