Hadrons in dense and hot matter

Theoretical issues and perspectives of hadronic matter at high baryon density are discussed with focus on the restoration of chiral symmetry and observable consequences.Received: 30 September 2002, Published online: 22 October 2003PACS: 25.75.-q Relativistic heavy-ion collisions - 21.65. + f Nuclear matter     

Neue Oxozincate der Alkalimetalle: Rb2[ZnO2] und Cs2[ZnO2]

New Oxozineates of Alkali Metals: Rb₂[ZnO₂] and Cs₂[ZnO₂] Colorless single crystals of the hitherto unknown Rb₂[ZnO₂] (a = 9.55₈, b = 6.33₅, c = 15.91 Å, β = 118.6°, z = 8, d_pyk = 4.11, d_rö = 4.21 g · cm^?3) and Cs₂[ZnO₂] (a = 9.85₁, b = 6.61₉, c = 16.26 Å, β = 116.8°) have been prepared, which crystallize monoclinic, P2₁/c – D. (For parameters see text.) Unexpected there are “isolated” groups [Zn₄O₈]. Half of the Zn atoms exhibit the unusual coordination number 3 towards O^2?. The Madelung Part of Lattice Energy, MAPLE, and the Effective Coordination Number, ECoN, the latter by means of Mean Fictive Ionic Radii, MEFIR, are calculated and discussed.     

Charge-exchange transitions in hot nuclei

A formalism based on the thermo field dynamics and allowing one to treat thermal effects on the strength distribution of charge-exchange transitions in hot nuclei is developed. The strength distributions of the allowed and first-forbidden p → n transitions are calculated for the neutron-rich nucleus ⁸⁰Ge at different temperatures. Then the electron capture rates on the same nucleus are calculated at temperatures and densities corresponding to an advanced stage of stellar evolution. Published in Russian in Yadernaya Fizika, 2009, Vol. 72, No. 8, pp. 1373–1384. The text was translated by the authors.     

Nature of low-energy dipole strength in nuclei: the case of a resonance at particle threshold in 208Pb

A high-resolution (gamma,gamma') study of the electric dipole response in 208Pb at the S-DALINAC reveals a resonance structure centered around the neutron emission threshold. Microscopic quasiparticle phonon model calculations in realistic model spaces including the coupling to complex configurations are able to describe the data in great detail. The resonance is shown to result from surface density oscillations of the neutron skin relative to an approximately isospin-saturated core. It also forms an integral part of a toroidal E1 mode representing an example of vortex collective motion in nuclei.     

Fine structure in the energy region of the isoscalar giant quadrupole resonance: characteristic scales from a wavelet analysis

Fine structure in the energy region of the isoscalar giant quadrupole resonance in nuclei is observed in high-resolution proton scattering experiments at iThemba LABS over a wide mass range. A novel method based on wavelet transforms is introduced for the extraction of scales characterizing the fine structure. A comparison with microscopic model calculations including two-particle two-hole (2p2h) degrees of freedom identifies the coupling to surface vibrations as the main source of the observed scales. A generic pattern is also found for the stochastic coupling to the background of the more complex states.     

The role of the continuum and the spurious 1− transitions in incoherent μ −−e− conversion rate calculations

By using the Continuum RPA (CRPA) method, the incoherent transition strength of the exotic μ ⁻−e⁻ conversion in nuclei is investigated. The question whether excited nuclear states lying high in the continuum give an important contribution to the incoherent rate is addressed. Results for ⁴⁰Ca are compared with those obtained previously for ²⁰⁸Pb. For both nuclei we then investigate in detail the admixture of spurious components in the rate coming from 1⁻ excitations, within the self-consistent CRPA with Skyrme interactions as well as within a less consistent version. We employ and compare two methods for removing the spurious strength: the use of effective operators, as done in a previous work for ²⁰⁸Pb, or simply the exclusion of the spurious state appearing close to zero energy. In all cases, the correction achieved is quite large. Presented by P. Papakonstantinou at the Workshop on calculation of double-beta-decay matrix elements (MEDEX’05), Corfu, Greece, September 26–29, 2005.