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Wolfram Weise

Publications and source records attributed to Wolfram Weise.

At least 91 records · Page 5Linked to original sources
arXiv2008

Variational calculation of the ppK^- system based on chiral SU(3) dynamics

The ppK^- system, as a prototype for possible quasibound Kbar nuclei,is investigated using a variational approach. Several versions of energy dependent effective KbarN interactions derived from chiral SU(3) dynamics are employed as input, together with a realistic NN potential (Av18). Taking into account theoretical uncertainties in the extrapolations below the KbarN threshold, we find that the antikaonic dibaryon ppK^- is NOT deeply bound. With the driving s-wave KbarN interaction the resulting total binding energy is B(ppK^-) = 20 $\pm$ 3 MeV and the mesonic decay width involving KbarN -> πY is expected to be in the range 40 - 70 MeV. Properties of this quasibound ppK^- system (such as density distributions of nucleons and antikaon) are discussed. The Λ(1405), as an I=0 quasi-bound state of Kbar and a nucleon, appears to survive in the ppK^- cluster. Estimates are given for the influence of p-wave KbarN interactions and for the width from two-nucleon absorption (KbarNN -> YN) processes. With inclusionof these effects and dispersive corrections from absorption, the ppK^- binding energy is expected to be in the range 20 - 40 MeV, while the total decay width can reach 100 MeV but with large theoretical uncertainties.

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arXiv2008

Effective Kbar N interaction with strong pi Sigma dynamics constrained by chiral SU(3) symmetry

We derive a single-channel effective Kbar N interaction from chiral SU(3) coupled-channel dynamics, emphasizing the important role of the pi Sigma channel and the structure of the Lambda(1405) resonance. The chiral low energy theorem requires strongly attractive interaction not only in the Kbar N channel but also in the pi Sigma channel. As a consequence of the strong pi Sigma dynamics, the equivalent potential in single Kbar N channel turns out to be less attractive than the one used in a purely phenomenological approach.

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arXiv2008

Effective Kbar N interaction based on chiral SU(3) dynamics

The effective Kbar N interaction based on chiral SU(3) coupled-channel dynamics is derived and its extrapolation below the Kbar N threshold is studied in detail. Starting from the coupled-channel scattering equations, we eliminate the channels other than Kbar N and obtain an effective interaction in the single Kbar N channel. An equivalent local potential in coordinate space is constructed such as to reproduce the full scattering amplitude of the chiral SU(3) coupled-channel framework. We discuss several realistic chiral SU(3)-based models in comparison to reach conclusions about the uncertainties involved. It turns out that, in the region relevant to the discussion of deeply bound Kbar-nuclear few-body systems, the resulting energy-dependent, equivalent local potential is substantially less attractive than the one suggested in previous purely phenomenological treatments.

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arXiv2008

Lambda(1405) in chiral SU(3) dynamics

We discuss several aspects of the Lambda(1405) resonance in relation to the recent theoretical developments in chiral dynamics. We derive an effective single-channel KbarK N interaction based on chiral SU(3) coupled-channel approach, emphasizing the important role of the pi Sigma channel and the structure of the Lambda(1405) in Kbar N phenomenology. In order to clarify the structure of the resonance, we study the behavior with the number of colors (Nc) of the poles associated with the Lambda(1405), and argue the physical meaning of the renormalization procedure.

hep-ph↗
arXiv2008

$K^-pp$ system with chiral SU(3) effective interaction

The $K^-pp$ system is investigated using a variational approach with realistic two-body interactions: the Argonne v18 $NN$ potential and an energy dependent $\bar{K}N$ effective interaction derived from chiral SU(3) coupled-channel dynamics. Uncertainties in subthreshold extrapolations of the $\bar{K}N$ interaction are considered. A weakly bound $K^-pp$ state is found, with a binding energy $B = (19\pm 3)$ MeV substantially smaller than suggested in previous calculations. The decay width $Γ(K^-pp\to πΣN)$ is estimated to range between about 40 and 70 MeV.

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arXiv2008

Overview and Perspectives in Nuclear Physics

This presentation reviews recent guiding themes in the broad context of nuclear physics, from developments in chiral effective field theory applied to nuclear systems, via the phases and structures of QCD, to matter under extreme conditions in heavy-ion collisions and neutron stars.

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arXiv2008

Chiral SU(3) Dynamics and Antikaon-Nuclear quasibound States

Recent developments are summarised concerning low-energy KbarN interactions as they relate to the possible existence of antikaon-nuclear quasibound states. An exploratory study of antikaons bound to finite nuclei is performed, with emphasis on the evolution of such states from light to heavy nuclei (A = 16 - 208). The energy dependent, driving attractive KbarN interactions are constructed using the s-wave coupled-channel amplitudes involving the Lambda(1405) and resulting from chiral SU(3) dynamics, plus p-wave amplitudes dominated by the Sigma(1385). Effects of Pauli and short-range correlations are discussed. The decay width induced by K^-NN two-body absorption is estimated and found to be substantial. It is concluded that Kbar-nuclear quasibound states can possibly exist with binding energies ranging from 60 to 100 MeV, but with short life times corresponding to decay widths of the similar magnitudes.

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arXiv2007

Phases of QCD, Polyakov Loop and Quasiparticles

QCD thermodynamics is studied using a model which combines Polyakov loop dynamics with spontaneous chiral symmetry breaking and its restoration (the PNJL model). The input is fixed entirely by pure-gauge lattice QCD results and by pion properties in vacuum. Successful comparisons with results from thermal lattice QCD are achieved, including extrapolations to finite quark chemical potential. The phase diagram and selected susceptibilities for two quark flavors are investigated with inclusion of diquark degrees of freedom.

hep-ph↗
arXiv2007

Yukawa's Pion, Low-Energy QCD and Nuclear Chiral Dynamics

A survey is given of the evolution from Yukawa's early work, via the understanding of the pion as a Nambu-Goldstone boson of spontaneously broken chiral symmetry in QCD, to modern developments in the theory of the nucleus based on the chiral effective field theory representing QCD in its low-energy limit.

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arXiv2007

Polyakov loop, diquarks and the two-flavour phase diagram

An updated version of the PNJL model is used to study the thermodynamics of N_f = 2 quark flavors interacting through chiral four-point couplings and propagating in a homogeneous Polyakov loop background. Previous PNJL calculations are extended by introducing explicit diquark degrees of freedom and an improved effective potential for the Polyakov loop field. The input is fixed exclusively by selected pure-gauge lattice QCD results and by pion properties in vacuum. The resulting (T, μ) phase diagram is studied with special emphasis on the critical point, its dependence on the quark mass and on Polyakov loop dynamics. We present successful comparisons with lattice QCD thermodynamics expanded to finite chemical potential μ.

hep-ph↗
arXiv2007

Study of light kaonic nuclei with a Chiral SU(3) - based KbarN interaction

We have investigated the prototype kaonic nucleus, $ppK^-$, using the method of Antisymmetrized Molecular Dynamics (AMD). In the present study we use a realistic $NN$ potential with strongly repulsive core, and a Chiral SU(3)-based $\bar{K}N$ interaction which is energy-dependent and includes both $s$- and p-wave interactions. We find that no self-consistent solutions exist when the range parameter of the $\bar{K}N$ interaction is less than 0.67 fm. Due to the strong repulsion of the $NN$ interaction at short distance, the two nucleons in $ppK^-$ keep a distance of about 1.2 fm and the total binding energy of $ppK^-$ does not exceed about 50 MeV in the scope of our current analysis.

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arXiv2007

Chiral SU(3) dynamics, KN interactions and the quest for antikaon-nuclear clusters

This presentation reviews recent developments in the understanding of low-energy kaon-nucleon interactions as they relate to the possible existence of antikaon-nuclear quasibound states. A state-of-the-art discussion of low-energy \bar{K}N interactions is given, with special emphasis on the subthreshold region relevant to the proposed kaon-nuclear systems.

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arXiv2007

Quark number susceptibilities: lattice QCD versus PNJL model

Quark number susceptibilities at finite quark chemical potential are investigated in the framework of the Polyakov-loop-extended Nambu Jona-Lasinio (PNJL) model. A detailed comparison is performed between the available lattice data, extrapolated using a Taylor expansion around vanishing chemical potential, and PNJL results consistently obtained from a Taylor series truncated at the same order. The validity of the Taylor expansion is then examined through a comparison between the full and truncated PNJL model calculations.

hep-ph↗
arXiv2006

Phase diagram and thermodynamics of the PNJL model

QCD-based thermodynamics at zero and finite quark chemical potential is studied using an extended Nambu and Jona-Lasinio approach in which quarks couple simultaneously to the chiral condensate and to a background temporal gauge field representing Polyakov loop dynamics. This so-called PNJL model thus includes features of both deconfinement and chiral symmetry restoration. We discuss the phase diagram as it emerges from this approach in close comparison with results from lattice QCD thermodynamics. The critical point, separating crossover from first order phase transition, is investigated with special focus on its quark mass dependence, starting from the relatively large masses presently accessible by lattice simulations, down to the chiral limit.

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arXiv2005

Deeply bound meson-nuclear states: concepts and strategies

This presentation reviews recent developments in the understanding of low-energy pion- and kaon-nucleon interactions as they relate to deeply bound pionic atoms and possible antikaon-nuclear bound states. A brief update is given on 1s states of pionic atoms, summarizing their theoretical interpretation based on in-medium chiral effective field theory. This is followed by a state-of-the-art discussion of low-energy $\bar{K}N$ interactions, with special emphasis on the subthreshold region relevant to the proposed kaon-nuclear systems.

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arXiv2005

The QCD vacuum and its hadronic excitations

A survey is given on selected topics of physics in the non-perturbative, hadronic sector of the QCD phase diagramme. Following a brief QCD primer, some highlights of Lattice QCD are summarised. Chiral effective field theory as the low-energy realisation of QCD is reviewed, with applications in pion-pion scattering, the scalar form factor of the nucleon and the interpolation of nucleon properties between lattice QCD results and actual observables. Chiral SU(3) dynamics, incorporating the strange quark, is developed with examples relating to low-energy kaon-nucleon interactions. The quest for quasiparticles in QCD and their correlations, beyond the simple partonic pictures of hadron structure, is discussed and aspects of QCD thermodynamics are explored in this context.

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arXiv2004

Nuclear density functional constrained by low-energy QCD

We have developed a relativistic point-coupling model of nuclear many-body dynamics constrained by the low-energy sector of QCD. The effective Lagrangian is characterized by density-dependent coupling strengths determined by chiral one- and two-pion exchange (with single and double delta isobar excitations) and by large isoscalar background fields that arise through changes of the quark condensate and the quark density at finite baryon density. The model has been tested in the analysis of nuclear ground-state properties along different isotope chains of medium and heavy nuclei. The agreement with experimental data is comparable with purely phenomenological predictions. The built-in QCD constraints and the explicit treatment of pion exchange restrict the freedom in adjusting parameters and functional forms of density-dependent couplings. It is shown that chiral pionic fluctuations play an important role for nuclear binding and saturation mechanism, whereas background fields of about equal magnitude and opposite sign generate the effective spin-orbit potential in nuclei.

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