Siegfried Krewald

Forschungszentrum Jülich

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Forschungszentrum Jülich

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Research Subjects

Nuclear Physics

Research Interests

Siegfried Krewald has a total of 168 co-authors. Here are the top co-authors by number of shared publications:

J. Speth
Forschungszentrum Jülich
36 shared publications
Ulf-Gerrit Meißner
Universität Bonn
33 shared publications
A. Sibirtsev
Universität Bonn
18 shared publications
Christoph Hanhart
Institute for Advanced Simulation, Forschungszentrum Jülich, D-52425 Jülich, Germany
18 shared publications
Johann Haidenbauer
Forschungszentrum Jülich
18 shared publications
K. Nakayama
Department of Physics and Astronomy, University of Athens, Georgia, USA
13 shared publications

Latest Publications

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Cited by 45
- 28 August 2012
- Published by American Physical Society (APS) in Physical Review Letters
Self-Consistent Calculations of the Electric Giant Dipole Resonances in Light and Heavy Nuclei
by N. Lyutorovich, V. I. Tselyaev, J. Speth, S. Krewald, F. Grümmer, P.-G. Reinhard
While bulk properties of stable nuclei are successfully reproduced by mean-field theories employing effective interactions, the dependence of the centroid energy of the electric giant dipole resonance on the nucleon number A is not. This problem is cured by considering many-particle correlations beyond mean-field theory, which we do within the quasiparticle time blocking approximation. The electric giant dipole resonances in O16, Ca40, and Pb208 are calculated using two new Skyrme interactions.
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- 28 August 2012
- Published by American Physical Society (APS) in Physical Review Letters
Self-Consistent Calculations of the Electric Giant Dipole Resonances in Light and Heavy Nuclei
by N. Lyutorovich, V. I. Tselyaev, J. Speth, S. Krewald, F. Grümmer, P.-G. Reinhard
While bulk properties of stable nuclei are successfully reproduced by mean-field theories employing effective interactions, the dependence of the centroid energy of the electric giant dipole resonance on the nucleon number A is not. This problem is cured by considering many-particle correlations beyond mean-field theory, which we do within the quasiparticle time blocking approximation. The electric giant dipole resonances in O16, Ca40, and Pb208 are calculated using two new Skyrme interactions.
Cited by 45
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Cited by 29
- 29 May 2012
- Published by American Physical Society (APS) in Physical Review C
Self-consistent calculations of quadrupole moments of the first 2 $^{+}$ states in Sn and Pb isotopes
by D. Voitenkov, S. Kamerdzhiev, S. Krewald, E. E. Saperstein, S. V. Tolokonnikov
A method of describing static moments of excited states and transitions between excited states is formulated for nonmagic nuclei within the Green's function formalism. Quadrupole moments of the first 2+ states in tin and lead isotope chains are calculated self-consistently using the energy density functional by Fayans et al. [Nucl. Phys. A 676, 49 (2000)]. Reasonable agreement with available experimental data is obtained. Quadrupole moments of unstable nuclei including 100Sn and 132Sn are predicted. A nontrivial dependence of the quadrupole moments on the neutron excess is found which can be traced to the negative proton contributions.
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- 29 May 2012
- Published by American Physical Society (APS) in Physical Review C
Self-consistent calculations of quadrupole moments of the first 2 $^{+}$ states in Sn and Pb isotopes
by D. Voitenkov, S. Kamerdzhiev, S. Krewald, E. E. Saperstein, S. V. Tolokonnikov
A method of describing static moments of excited states and transitions between excited states is formulated for nonmagic nuclei within the Green's function formalism. Quadrupole moments of the first 2+ states in tin and lead isotope chains are calculated self-consistently using the energy density functional by Fayans et al. [Nucl. Phys. A 676, 49 (2000)]. Reasonable agreement with available experimental data is obtained. Quadrupole moments of unstable nuclei including 100Sn and 132Sn are predicted. A nontrivial dependence of the quadrupole moments on the neutron excess is found which can be traced to the negative proton contributions.
Cited by 29
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Cited by 29
- 23 May 2012
- Published by Springer Nature in The European Physical Journal A
Quadrupole moments of spherical semi-magic nuclei within the self-consistent Theory of Finite Fermi Systems
by S. V. Tolokonnikov, S. Kamerdzhiev, S. Krewald, E. E. Saperstein, D. Voitenkov
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- 23 May 2012
- Published by Springer Nature in The European Physical Journal A
Quadrupole moments of spherical semi-magic nuclei within the self-consistent Theory of Finite Fermi Systems
by S. V. Tolokonnikov, S. Kamerdzhiev, S. Krewald, E. E. Saperstein, D. Voitenkov
Cited by 29
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Cited by 87
- 16 May 2012
- Published by American Physical Society (APS) in Physical Review C
Pion photoproduction in a dynamical coupled-channels model
by F. Huang, M. Döring, H. Haberzettl, J. Haidenbauer, C. Hanhart, S. Krewald, U.-G. Meißner, K. Nakayama
The charged and neutral pion photoproduction reactions are investigated in a dynamical coupled-channels approach based on the formulation of Haberzettl, Huang, and Nakayama [ Phys. Rev. C 83, 065502 (2011)]. The hadronic final-state interaction is provided by the Jülich $π N$ model, which includes the channels $π N$ and $η N$ comprising stable hadrons as well as the effective $π π N$ channels $π Δ$ , $σ N$ , and $ρ N$ . This hadronic model has been quite successful in describing $π N \to π N$ scattering for center-of-mass energies up to $1.9$ GeV. By construction, the full pion photoproduction current satisfies the generalized Ward-Takahashi identity and thus is gauge invariant as a matter of course. The calculated differential cross sections and photon spin asymmetries up to 1.65 GeV center-of-mass energy for the reactions $γ p \to π^{+} n$ , $γ p \to π^{0} p$ , $γ n \to π^{-} p$ , and $γ n \to π^{0} n$ are in good agreement with the experimental data.
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- 16 May 2012
- Published by American Physical Society (APS) in Physical Review C
Pion photoproduction in a dynamical coupled-channels model
by F. Huang, M. Döring, H. Haberzettl, J. Haidenbauer, C. Hanhart, S. Krewald, U.-G. Meißner, K. Nakayama
The charged and neutral pion photoproduction reactions are investigated in a dynamical coupled-channels approach based on the formulation of Haberzettl, Huang, and Nakayama [ Phys. Rev. C 83, 065502 (2011)]. The hadronic final-state interaction is provided by the Jülich $π N$ model, which includes the channels $π N$ and $η N$ comprising stable hadrons as well as the effective $π π N$ channels $π Δ$ , $σ N$ , and $ρ N$ . This hadronic model has been quite successful in describing $π N \to π N$ scattering for center-of-mass energies up to $1.9$ GeV. By construction, the full pion photoproduction current satisfies the generalized Ward-Takahashi identity and thus is gauge invariant as a matter of course. The calculated differential cross sections and photon spin asymmetries up to 1.65 GeV center-of-mass energy for the reactions $γ p \to π^{+} n$ , $γ p \to π^{0} p$ , $γ n \to π^{-} p$ , and $γ n \to π^{0} n$ are in good agreement with the experimental data.
Cited by 87
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Cited by 10
- 1 April 2012
- Published by Elsevier in Progress in Particle and Nuclear Physics
Effective field theory approach to nuclear matter
by S. Krewald, E. Epelbaum, U.-G. Meißner, P. Saviankou
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- 1 April 2012
- Published by Elsevier in Progress in Particle and Nuclear Physics
Effective field theory approach to nuclear matter
by S. Krewald, E. Epelbaum, U.-G. Meißner, P. Saviankou
Cited by 10
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Cited by 50
- 27 December 2011
- Published by American Physical Society (APS) in Physical Review C
Effects of density dependence of the effective pairing interaction on the first $2^{+}$ excitations and quadrupole moments of odd nuclei
by S. V. Tolokonnikov, S. Kamerdzhiev, D. Voitenkov, S. Krewald, E. E. Saperstein
Excitation energies and transition probabilities of the first 2+ excitations in even tin and lead isotopes as well as the quadrupole moments of odd neighbors of these isotopes are calculated within the self-consistent theory of finite Fermi systems based on the energy density functional by Fayans et al. [Nucl. Phys. A 676, 49 (2000)]. The effect of the density dependence of the effective pairing interaction is analyzed in detail by comparing results obtained with volume and surface pairing. The effect is found to be noticeable. For example, the 2+ energies are systematically higher at 200\char21{}400 keV for the volume paring as compared with the surface-pairing case. However, on the average, both models reasonably agree with the data. Quadrupole moments of odd-neutron nuclei are very sensitive to the single-particle energy of the state $\lambda${} under consideration owing to the Bogolyubov factor (u$\lambda${}2$-${}v$\lambda${}2). A reasonable agreement with experiment for the quadrupole moments has been obtained for the most part of odd nuclei considered. The method used gives a reliable possibility to predict quadrupole moments of unstable odd nuclei, including very neutron rich ones.
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- 27 December 2011
- Published by American Physical Society (APS) in Physical Review C
Effects of density dependence of the effective pairing interaction on the first $2^{+}$ excitations and quadrupole moments of odd nuclei
by S. V. Tolokonnikov, S. Kamerdzhiev, D. Voitenkov, S. Krewald, E. E. Saperstein
Excitation energies and transition probabilities of the first 2+ excitations in even tin and lead isotopes as well as the quadrupole moments of odd neighbors of these isotopes are calculated within the self-consistent theory of finite Fermi systems based on the energy density functional by Fayans et al. [Nucl. Phys. A 676, 49 (2000)]. The effect of the density dependence of the effective pairing interaction is analyzed in detail by comparing results obtained with volume and surface pairing. The effect is found to be noticeable. For example, the 2+ energies are systematically higher at 200\char21{}400 keV for the volume paring as compared with the surface-pairing case. However, on the average, both models reasonably agree with the data. Quadrupole moments of odd-neutron nuclei are very sensitive to the single-particle energy of the state $\lambda${} under consideration owing to the Bogolyubov factor (u$\lambda${}2$-${}v$\lambda${}2). A reasonable agreement with experiment for the quadrupole moments has been obtained for the most part of odd nuclei considered. The method used gives a reliable possibility to predict quadrupole moments of unstable odd nuclei, including very neutron rich ones.
Cited by 50
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- 25 October 2011
- Published by AIP Publishing in AIP Conference Proceedings
Jülich-Georgia meson-baryon model
by M. Döring, C. Hanhart, F. Huang, S. Krewald, K. Nakayama, U.-G. Meißner, David Armstrong, Volker Burkert, Jian-Ping Chen, Will Detmold, et al.
Meson‐baryon scattering and photon‐nucleon reactions are described in a coupled‐channel approach for energies below 2 GeV. Poles and residues of the reaction amplitudes are obtained by analytical continuation. The dependence of the resonance poles on the pion mass is investigated.
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- 25 October 2011
- Published by AIP Publishing in AIP Conference Proceedings
Jülich-Georgia meson-baryon model
by M. Döring, C. Hanhart, F. Huang, S. Krewald, K. Nakayama, U.-G. Meißner, David Armstrong, Volker Burkert, Jian-Ping Chen, Will Detmold, et al.
Meson‐baryon scattering and photon‐nucleon reactions are described in a coupled‐channel approach for energies below 2 GeV. Poles and residues of the reaction amplitudes are obtained by analytical continuation. The dependence of the resonance poles on the pion mass is investigated.
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- 25 October 2011
- Published by AIP Publishing in AIP Conference Proceedings
Pion photoproduction in a dynamical coupled-channel model
by F. Huang, M. Döring, H. Haberzettl, S. Krewald, K. Nakayama, David Armstrong, Volker Burkert, Jian-Ping Chen, Will Detmold, Jo Dudek, et al.
Pion photoproduction reactions are investigated in a dynamical coupled‐channel approach based on the Jülich πN model, which presently includes the hadronic πN and ηN stable channels as well as the πΔ, σN and ρN effective channels. This model has been quite successful in the description of $πN→πN$ scattering for center‐of‐mass energies up to 1.9 GeV. The full pion photoproduction amplitude is constructed to satisfy the generalized Ward‐Takahashi identity and hence, it is fully gauge invariant. The calculated differential cross sections and photon spin asymmetries up to 1.65 GeV center‐of‐mass energy for the reactions ${γp→π}^{+} n,$ ${γp→π}^{0} p$ and ${γn→π}^{-} p$ are in good agreement with the experimental data.
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- 25 October 2011
- Published by AIP Publishing in AIP Conference Proceedings
Pion photoproduction in a dynamical coupled-channel model
by F. Huang, M. Döring, H. Haberzettl, S. Krewald, K. Nakayama, David Armstrong, Volker Burkert, Jian-Ping Chen, Will Detmold, Jo Dudek, et al.
Pion photoproduction reactions are investigated in a dynamical coupled‐channel approach based on the Jülich πN model, which presently includes the hadronic πN and ηN stable channels as well as the πΔ, σN and ρN effective channels. This model has been quite successful in the description of $πN→πN$ scattering for center‐of‐mass energies up to 1.9 GeV. The full pion photoproduction amplitude is constructed to satisfy the generalized Ward‐Takahashi identity and hence, it is fully gauge invariant. The calculated differential cross sections and photon spin asymmetries up to 1.65 GeV center‐of‐mass energy for the reactions ${γp→π}^{+} n,$ ${γp→π}^{0} p$ and ${γn→π}^{-} p$ are in good agreement with the experimental data.
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- 18 August 2011
- Published by Pleiades Publishing Ltd in Physics of Atomic Nuclei
Migdal and his theory in Jülich
by J. Speth, F. Grümmer, S. Krewald
We review the application of Migdal’s Theory of Finite Fermi Systems to the structure of deformed nuclei, approaches beyond the conventional linear response, and microscopic calculations of the Migdal-parameters.
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- 18 August 2011
- Published by Pleiades Publishing Ltd in Physics of Atomic Nuclei
Migdal and his theory in Jülich
by J. Speth, F. Grümmer, S. Krewald
We review the application of Migdal’s Theory of Finite Fermi Systems to the structure of deformed nuclei, approaches beyond the conventional linear response, and microscopic calculations of the Migdal-parameters.
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Cited by 67
- 15 July 2011
- Published by American Physical Society (APS) in Physical Review C
Relevance of complex branch points for partial wave analysis
by S. Ceci, M. Döring, C. Hanhart, S. Krewald, U.-G. Meißner, A. Švarc
A central issue in hadron spectroscopy is to deduce—and interpret—resonance parameters, namely, pole positions and residues, from experimental data, for those are the quantities to be compared to lattice QCD or model calculations. However, not every structure in the observables derives from a resonance pole: the origin might as well be branch points, either located on the real axis (when a new channel composed of stable particles opens) or in the complex plane (when at least one of the intermediate particles is unstable). In this paper we demonstrate first the existence of such branch points in the complex plane and then show on the example of the $π N$ $P_{11}$ partial wave that it is not possible to distinguish the structures induced by the latter from a true pole signal based on elastic data alone.
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- 15 July 2011
- Published by American Physical Society (APS) in Physical Review C
Relevance of complex branch points for partial wave analysis
by S. Ceci, M. Döring, C. Hanhart, S. Krewald, U.-G. Meißner, A. Švarc
A central issue in hadron spectroscopy is to deduce—and interpret—resonance parameters, namely, pole positions and residues, from experimental data, for those are the quantities to be compared to lattice QCD or model calculations. However, not every structure in the observables derives from a resonance pole: the origin might as well be branch points, either located on the real axis (when a new channel composed of stable particles opens) or in the complex plane (when at least one of the intermediate particles is unstable). In this paper we demonstrate first the existence of such branch points in the complex plane and then show on the example of the $π N$ $P_{11}$ partial wave that it is not possible to distinguish the structures induced by the latter from a true pole signal based on elastic data alone.
Cited by 67

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