Correlations between resonances in a statistical scattering model

The distortion of the regular motion in a quantum system by its coupling to the continuum of decay channels is investigated. The regular motion is described by means of a Poissonian ensemble. We focus on the case of only few channels K<10. The coupling to the continuum induces two main effects, due to which the distorted system differs from a chaotic system (described by a Gaussian ensemble): 1. The width distribution for large coupling becomes broader than the corresponding $\chi^2_K$ distribution in the GOE case. 2. Due to the coupling to the continuum, correlations are induced not only between the positions of the resonances but also between positions and widths. These correlations remain even in the strong coupling limit. In order to explain these results, an asymptotic expression for the width distribution is derived for the one channel case. It relates the width of a trapped resonance state to the distance between its two neighboring levels.Comment: 23 pages, 7 Postscript figures. Submitted to Phys. Rev. E, Jan. 9

Bethe-Salpeter Amplitudes and Static Properties of the Deuteron

Extended calculations of the deuteron's static properties, based on the numerical solution of the Bethe-Salpeter equation, are presented. A formalism is developed, which provides a comparative analysis of the covariant amplitudes in various representations and nonrelativistic wave functions. The magnetic and quadrupole moments of the deuteron are calculated in the Bethe-Salpeter formalism and the role of relativistic corrections is discussed.Comment: 33 pages ([aps]{revtex} style), 9 Postscript figures; (55 pages if [preprint,aps]{revtex} style is used

Mikroskopische Theorie intrinsischer magnetischer Eigenschaften von Seltenerd-Uebergangsmetall-Verbindungen in kompakten Proben und in duennen Schichten Abschlussbericht

Intrinsic magnetic properties (polarization, anisotropy field, Curie temperature) of potentially hard magnetic compounds RT_1_2X_n and R_2T_1_7X_n sensitively depend on chemical composition and crystal structure. Our aim is to understand the relations between structure and properties of the abovementioned systems with the help of microscopic-theoretical models. Coupling of density functional calculations with microscopic model theories. We have performed conceptual developments (computer codes, adiabatic theory of Spin dynamics) as well as specific calculations for particular properties of the systems under consideration. 2:17 systems: selective impact of volume and chemical changes, results are relevant for the development of new materials; 1:12-systems: strong sensitivity of the magnetic anisotropy with respect to the lattice geometry, the understanding of interface properties will depend upon detailed structural knowledge. (orig.)SIGLEAvailable from TIB Hannover: DtF QN1(64,60) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Untersuchungen zur Quantenelektrodynamik und zur Anregung subnuklearer Freiheitsgrade in Schwerionenkollisionen Abschlussbericht

SIGLEAvailable from TIB Hannover: DtF QN1(66,53) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Magnetische Texturbestimmung und magnetische Viskositaet von modifizierten Neodym-Eisen-Bohr-Dauermagneten Abschlussbericht

SIGLEAvailable from TIB Hannover: D.Dt.F.QN1(18,33) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman

Synthese, Stoff- und Struktureigenschaften oxidischer Materialien (HTSL) Abschlussbericht

Available from TIB Hannover: FR 6840+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

New hunt for an intermediate-mass Higgs boson in peripheral ultrarelativistic heavy-ion collisions

We reopen the discussion on the two-photon production of the intermediate mass Higgs boson in peripheral ultrarelativistic heavy-ion collisions at LHC. Due to larger expected luminosity, larger collision energy and higher photon energies the Higgs production rate is enlarged by more than a factor of ten in Ca+Ca collisions compared to Pb+Pb collisions. Besides the background of direct b anti b-production via two-photon function we also discuss photon-gluon fusion into b anti b. (orig.)Available from TIB Hannover: RO 801(95-27) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Deduction of the in-medium gluon distribution from photon-gluon fusion processes in peripheral ultrarelativisitic heavy-ion collisions

The photon-gluon fusion process into a pair of heavy quarks is studied for peripheral Pb+Pb collisions at LHC energies. The double differential cross section with respect to the invariant mass and the rapidity of the produced quark pair at zero rapidity is directly proportional to the gluon distribution in the nuclear medium. Differential cross sections for the b-quark production lie well in the #mu#barn/GeV regime which will allow the deduction of the gluon distribution at low x. Rapidity cuts for the actual detectors are also considered. (orig.)Available from TIB Hannover: RO 801(94-42) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Evidence for low freeze-out temperature and large transverse flow in central collisions of Pb+Pb at 158 AGeV

Utilizing a hydrodynamical model for the freeze-out stage in heavy-ion reactions, we extract from resolved transverse hadron spectra at midrapidity an inverse slope parameter (temperature) T_P_b = 120 MeV and an averaged transverse flow velocity v&quot;a&quot;v&quot;e&quot;r _p_e_r_p_e_n_d_i_c_u_l_a_r _t_o _P_b = 0.43 c in central collisions of Pb + Pb at 158 AGeV. (orig.)11 refs.Available from TIB Hannover: RR 1847(149) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Description of an open quantum mechanical system

A model for the description of an open quantum mechanical many-particle system is formulated. It starts from the shell model and treats the continuous states by a coupled channels method. The mixing of the discrete shell model states via the continuum of decay channels results in the genuine decaying states of the system. These states are eigenstates of a non-Hermitean Hamilton operator the eigenvalues of which give both the energies and the widths of the states. All correlations between two particles which are caused by the two-particle residual interaction, are taken into account including those via the continuum. In the formalism describing the open quantum mechanical system, the coupling between the system and its environment appears nonlinearly. If the resonance states start to overlap, a redistribution of the spectroscopic values ('trapping effect') takes place. As a result, the complexity of the system is reduced at high level density, structures in space and time are formed. This redistribution describes, on the one hand, the transition from the well-known nuclear properties at low level density to those at high level density and fits, on the other hand, into the concept of selforganization. (orig.)Available from TIB Hannover: RR 1847(94-42) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman