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Fri, 14 Jul 2006 10:13:20 +0200Fri, 14 Jul 2006 10:13:20 +0200Potential energy surfaces of superheavy nuclei
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2392
We investigate the structure of the potential energy surfaces of the superheavy nuclei 158258Fm100, 156264Hs108, 166278112, 184298114, and 172292120 within the framework of self-consistent nuclear models, i.e., the Skyrme-Hartree-Fock approach and the relativistic mean-field model. We compare results obtained with one representative parametrization of each model which is successful in describing superheavy nuclei. We find systematic changes as compared to the potential energy surfaces of heavy nuclei in the uranium region: there is no sufficiently stable fission isomer any more, the importance of triaxial configurations to lower the first barrier fades away, and asymmetric fission paths compete down to rather small deformation. Comparing the two models, it turns out that the relativistic mean-field model gives generally smaller fission barriers.Michael Bender; Klemens Rutz; Paul-Gerhard Reinhard; Joachim A. Maruhn; Walter Greinerarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2392Fri, 14 Jul 2006 10:13:20 +0200Shell structure of superheavy nuclei in self-consistent mean-field models
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2390
We study the extrapolation of nuclear shell structure to the region of superheavy nuclei in self-consistent mean-field models—the Skyrme-Hartree-Fock approach and the relativistic mean-field model—using a large number of parametrizations which give similar results for stable nuclei but differ in detail. Results obtained with the folded-Yukawa potential which is widely used in macroscopic-macroscopic models are shown for comparison. We focus on differences in the isospin dependence of the spin-orbit interaction and the effective mass between the models and their influence on single-particle spectra. The predictive power of the mean-field models concerning single-particle spectra is discussed for the examples of 208Pb and the spin-orbit splittings of selected neutron and proton levels in 16O, 132Sn, and 208Pb. While all relativistic models give a reasonable description of spin-orbit splittings, all Skyrme interactions show a wrong trend with mass number. The spin-orbit splitting of heavy nuclei might be overestimated by 40%–80%, which exposes a fundamental deficiency of the current nonrelativistic models. In most cases the occurrence of spherical shell closures is found to be nucleon-number dependent. Spherical doubly magic superheavy nuclei are found at 184298114, 172292120, or 184310126 depending on the parametrization. The Z=114 proton shell closure, which is related to a large spin-orbit splitting of proton 2f states, is predicted only by forces which by far overestimate the proton spin-orbit splitting in 208Pb. The Z=120 and N=172 shell closures predicted by the relativistic models and some Skyrme interactions are found to be related to a central depression of the nuclear density distribution. This effect cannot appear in macroscopic-microscopic models or semiclassical approaches like the extended Thomas-Fermi-Strutinski integral approach which have a limited freedom for the density distribution only. In summary, our findings give a strong argument for 172292120 to be the next spherical doubly magic superheavy nucleus.Michael Bender; Klemens Rutz; Paul-Gerhard Reinhard; Joachim A. Maruhn; Walter Greinerarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2390Fri, 14 Jul 2006 10:11:29 +0200Optimal parametrization for the relativistic mean-field model of the nucleus
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2418
We study a relativistic model of the nucleus consisting of nucleons coupled to mesonic degrees of freedom via an effective Lagrangian whose parameters are determined by a fit to selected nuclear ground-state data. We find that the model allows a very good description of nuclear ground-state properties. Because of the relativistic nature of the model, the spin properties are uniquely fixed. We discuss variations of the parametrization and of the data which suggest that the present fit has exhausted the limits of the mean-field approximation, and discuss extensions which go beyond the mean field.M. Rufa; P.-G. Reinhard; Joachim A. Maruhn; Walter Greiner; M. R. Strayerarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2418Fri, 07 Jul 2006 16:30:53 +0200Nuclear equation of state from the nonlinear relativistic mean field theory
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2417
The properties of symmetric nuclear matter are investigated in the nonlinear relativistic mean field theory of nuclear matter. We consider the constraints imposed by four nuclear ground state properties on the coupling constants and on the equation of state at zero and at finite temperature. We find that the compression constant K(ρ0) as well as the temperature is irrelevant for the stiffness of the equation of state for m*(ρ0)≤0.7. The main point is that the relativistic mean field theory exhibits acausal and unphysical behavior for compressibilities below K(ρ0)=200 MeV. Every set of coupling constants with a negative quartic coupling constant c is unstable against small quantum fluctuations.B. M. Waldhauser; Joachim A. Maruhn; Horst Stöcker; Walter Greinerarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2417Fri, 07 Jul 2006 16:20:32 +0200Three-component fluid dynamics for the description of energetic heavy-ion reactions
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2469
The nucleons taking part in heavy ion reaction are considered as a three-component fluid. The first and second components correspond to the nucleons of the target and the projectile, while the thermalized nucleons produced in the course of the collision belong to the third component. Making use of the Boltzmann equation, hydrodynamical equations are derived. An equation of state for anisotropic nuclear matter obtained from a field theoretical model in mean field approximation is applied in a one dimensional version of the three-component fluid model. The speed of thermalization is analyzed and compared to the results of cascade and kinetic models. NUCLEAR REACTIONS Relativistic heavy-ion reactions, hydrodynamic description.László Pal Csernai; I. Lovas; Joachim A. Maruhn; A. J Rosenhauer; J. Zimányi; Walter Greinerarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2469Fri, 30 Jun 2006 12:51:03 +0200Different deformations of proton and neutron distributions in nuclei
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2477
Different collective deformation coordinates for neutrons and protons are introduced to allow for both stretching and γ transitions consistent with experiments. The rotational actinide nuclei 234-238U and 232Th are successfully analyzed in this model. NUCLEAR STRUCTURE 232Th, 234-238U calculated B (E2) values, collective model.M. Seiwert; P. O. Hess; Joachim A. Maruhn; Walter Greinerarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2477Fri, 30 Jun 2006 10:48:59 +0200Collective effects on mass asymmetry in fission
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2515
the development of the mass asymmetry vibrations in the final stages of the fission process is studied with an approximate treatment of the coupling to relative motion. A parametrized friction is introduced and its effects are studied. Numerical results are presented for 236U, together with estimates for the kinetic energy of the fragments. RADIOACTIVITY, FISSION 236U; calculated mass distribution, kinetic energy distribution. Collective dynamics, shell correction method, cranking model.Joachim A. Maruhn; Walter Greinerarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2515Tue, 27 Jun 2006 15:15:17 +0200Theory of fission-mass distributions demonstrated for 226Ra, 236U, 258Fm
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2520
With the mass asymmetry described by the dynamical collective fragmentation coordinate ξ, and with use of the asymmetric two-center shell model, the fission mass distributions for 226Ra, 236U, and 258Fm (which are typical representatives for triple-, double-, and single-humped distributions) are explained.Joachim A. Maruhn; Walter Greinerarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2520Tue, 27 Jun 2006 14:27:03 +0200Variable masses in fission and heavy-ion collisions
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2525
With the use of the cranking formula, the coordinate-dependent mass parameters of the kinetic-energy operator in fission processes and heavy-ion collisions are calculated in the two-center oscillator model. It is shown that the reduced mass and also the classical moment of inertia are obtained for large separations of the fragments. For small separations, however, the mass parameter for the motion of the centers of mass of the fragments is larger than the reduced mass by an order of magnitude.Peter Lichtner; Dieter Drechsel; Joachim A. Maruhn; Walter Greinerarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2525Mon, 26 Jun 2006 13:15:02 +0200Collective sideward flow of nuclear matter in violent high-energy heavy-ion collisions
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2585
Angular and energy distributions of fragments emitted from fast nucleus-nucleus collisions (Ne--> U at 250, 400, and 800 MeV/N) are calculated with use of nuclear fluid dynamics. A characteristic dependence of the energy spectra and angular distributions on the impact parameter is predicted. The preferential sideward emission of reaction fragments observed in the calculation for nearly central collisions seems to be supported by recent experimental data.Horst Stöcker; Joachim A. Maruhn; Walter Greinerarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2585Tue, 20 Jun 2006 10:44:52 +0200Importance of nuclear viscosity and thermal conductivity and the analysis of the bounce-off effect in high energy heavy ion collisions
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2584
We present an analysis of high energy heavy ion collisions at intermediate impact parameters, using a two-dimensional fluid-dynamical model including shear and bulk viscosity, heat conduction, a realistic treatment of the nuclear binding, and an analysis of the final thermal emission of free nucleons. We find large collective momentum transfer to projectile and target residues (the highly inelastic bounce-off effect) and explosion of the hot compressed shock zones formed during the impact. As the calculated azimuthal dependence of energy spectra and angular distributions of emitted nucleons depends strongly on the coefficients of viscosity and thermal conductivity, future exclusive measurements may allow for an experimental determination of these transport coefficients. The importance of 4π measurements with full azimuthal information is pointed out.Gerd Buchwald; László Pal Csernai; Joachim A. Maruhn; Walter Greiner; Horst Stöckerarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2584Tue, 20 Jun 2006 10:41:14 +0200Jets of nuclear matter from high energy heavy ion collisions
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2625
The fluid dynamical model is used to study the reactions 20Ne+238U and 40Ar+40Ca at Elab=390 MeV/nucleon. The calculated double differential cross sections d2σ/dΩdE exhibit sidewards maxima in agreement with recent experimental data. The azimuthal dependence of the triple differential distributions, to be obtained from an event-by-event analysis of 4π exclusive experiments, can yield deeper insight into the collision process: Jets of nuclear matter are predicted with a strongly impact-parameter-dependent thrust angle θjet(b). NUCLEAR REACTIONS Ar+Ca, Ne+U, Elab=393 MeV/nucleon, fluid dynamics with thermal breakup, double differential cross sections, azimuthal dependence of triple differential cross sections, event-by-event thrust analysis of 4π exclusive experiments.Horst Stöcker; László Pal Csernai; Gerhard Graebner; Gerd Buchwald; Hans Kruse; R. Y. Cusson; Joachim A. Maruhn; Walter Greinerarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2625Tue, 13 Jun 2006 12:52:18 +0200Viscous fluid dynamical calculation of the reaction 12C(85 MeV/nucleon) + 197Au
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2622
Proton spectra have been calculated for the reaction 12C(85 MeV/nucleon) + 197Au using a three-dimensional hydrodynamical model with viscosity and thermal conductivity and final thermal breakup. The theoretical results are compared to recent data. It is shown that the predicted flow effects are not observable as a result of the impact parameter averaging inherent in the inclusive proton spectra. In contrast, angular distributions of medium mass nuclei (A>3) in nearly central collisions can provide signatures for flow effects.Gerd Buchwald; Gerhard Graebner; J. Theis; Joachim A. Maruhn; Walter Greiner; Horst Stöckerarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2622Tue, 13 Jun 2006 12:42:16 +0200Time-dependent Hartree-Fock studies of superheavy molecules
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2621
The time dependent Hartree-Fock approximation is used to study the dynamical formation of long-lived superheavy nuclear complexes. The effects of long-range Coulomb polarization are treated in terms of a classical quadrupole polarization model. Our calculations show the existence of "resonantlike" structures over a narrow range of bombarding energies near the Coulomb barrier. Calculations of 238U + 238U are presented and the consequences of these results for supercritical positron emission are discussed. NUCLEAR REACTIONS 238U + 238U collisions as a function of bombarding energy, in the time-dependent Hartree-Fock approximation. Superheavy molecules and strongly damped collisions.M. R. Strayer; R. Y. Cusson; Horst Stöcker; Joachim A. Maruhn; Walter Greinerarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2621Tue, 13 Jun 2006 12:36:41 +0200Kinetic energy flow in Nb(400 A MeV) + Nb: evidence for hydrodynamic compression of nuclear matter
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2617
A kinetic-energy—flow analysis of multiplicity-selected collisions of 93Nb(Elab=400A MeV)+93Nb is performed on the basis of the nuclear fluid dynamical model. The effects of finite particle numbers on the flow tensor are explicitly taken into account. Strong sidewards peaks are predicted in dN/dcosθF, the distribution of event by event flow angles. This is in qualitative agreement with recent data from the "Plastic Ball" electronic detection system. Cascade simulations fail to reproduce the data.Gerd Buchwald; Gerhard Graebner; J. Theis; Joachim A. Maruhn; Walter Greiner; Horst Stöckerarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2617Tue, 13 Jun 2006 11:34:49 +0200Influence of shape fluctuations in relativistic heavy ion collisions
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2643
The influence of fluctuations of the shape degree of freedom in collisions of deformed nuclei with energies between 0.8 and 2.1 GeV/nucleon is analyzed on the basis of an intranuclear cascade simulation for the strongly deformed systems 46Ti+ 46Ti and 166Er+ 166Er. While there is a considerable sensitivity of the global event variables to the orientation for polarized beams and targets, this dependence disappears in the average over all orientations for impact parameter selected and integrated events. The dependence of the nuclear stopping and thermalization on the size of the system under consideration and on the bombarding energy is also investigated.A. Rosenhauer; Horst Stöcker; Joachim A. Maruhn; Walter Greinerarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2643Mon, 12 Jun 2006 11:09:10 +0200Phase transition of the nucleon-antinucleon plasma in a relativistic mean-field theory
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2640
Studying Walecka's mean-field theory we find that one can reproduce the observed binding energy and density of nuclear matter within experimental precision in an area characterized by a line in the coupling-constant plane. A part of this line defines systems which exhibit a phase transition around Tc~200 MeV for zero baryon density. The rest corresponds to such systems where the phase transition is absent; in that case a peak appears in the specific heat around T~200 MeV. We interpret these results as indicating that the hadron phase of nuclear matter alone indicates the occurrence of an abrupt change in the bulk properties around ρV~0 and T~200 MeV.J. Theis; Gerhard Graebner; Gerd Buchwald; Joachim A. Maruhn; Walter Greiner; Horst Stöcker; J. Polonyiarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2640Mon, 12 Jun 2006 10:54:49 +0200Fragment emission in high-energy heavy-ion reactions
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2646
We present a theoretical description of nuclear collisions which consists of a three-dimensional fluid-dynamical model, a chemical equilibrium breakup calculation for local light fragment (i.e., p, n, d, t, 3He, and 4He) production, and a final thermal evaporation of these particles. The light fragment cross sections and some properties of the heavy target residues are calculated for the asymmetric system Ne+U at 400 MeV/N. The results of the model calculations are compared with recent experimental data. Several observable signatures of the collective hydrodynamical processes are consistent with the present data. An event-by-event analysis of the flow patterns of the various clusters is proposed which can yield deeper insight into the collision dynamics.László Pal Csernai; Horst Stöcker; Pal R. Subramanian; Gerd Buchwald; Gerhard Graebner; Albrecht Rosenhauer; Joachim A. Maruhn; Walter Greinerarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2646Mon, 12 Jun 2006 10:51:42 +0200Event-by-event analysis : possible testing ground for the nuclear matter equation of state
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2645
Intranuclear cascade calculations and fluid dynamical predictions of the kinetic energy flow are compared for collisions of 40Ca + 40Ca and 238U + 238U. The aspect ratio, R13, as obtained from the global analysis, is independent of the bombarding energy for the intranuclear cascade model. Fluid dynamics, on the other hand, predicts a dramatic increase of R13 at medium energies Elab≲200 MeV/nucleon. In fact, R13(Elab) directly reflects the incompressibility of the nuclear matter and can be used to extract the nuclear equation of stat at high densities. Distortions of the flow tensor due to few nucleon scattering are analyzed. Possible procedures to remove this background from experimental data are discussed.Gerd Buchwald; Gerhard Graebner; J. Theis; Joachim A. Maruhn; Walter Greiner; Horst Stöcker; K .A. Frankel; Miklos Gyulassyarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2645Mon, 12 Jun 2006 10:41:03 +0200Phase structure of excited baryonic matter in the relativistic mean field theory
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2651
We analyze the phase structure of the nonlinear mean-field meson theory of baryonic matter (nucleons plus delta resonances). Depending on the choice of the coupling constants, we find three physically distinct phase transitions in this theory: a nucleonic liquid-gas transition in the low temperature, Tc<20 MeV, low density, ρ≃0.5ρ0, regime, a high-temperature (T≃150 MeV) finite density transition from a gas of massive hadrons to a nearly massless baryon, antibaryon plasma, and, third, a strong phase transition from the nucleonic fluid to a resonance-dominated ‘‘delta-matter’’ isomer at ρ>2ρ0 and Tc<50 MeV. All three phase transitions are of first order. It is shown that the occurrence of these different phase transitions depends critically on the coupling constants. Since the production of pions also depends strongly on the coupling constants, it is seen that the equation of state cannot be derived unambiguously from pion data.B. M. Waldhauser; J. Theis; Joachim A. Maruhn; Horst Stöcker; Walter Greinerarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2651Fri, 09 Jun 2006 10:46:06 +0200Multi-lambda hypernuclei and the equation of state of hypermatter
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2674
Einschl.: Erratum: Multi-lambda hypernuclei and the equation of state of hypermatter, Phys. Rev. C 43, 2020 (1991), http://link.aps.org/abstract/PRC/v43/p2020M. Rufa; J. Schaffner; Joachim A. Maruhn; Horst Stöcker; Walter Greiner; P.-G. Reinhardarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2674Fri, 02 Jun 2006 14:45:52 +0200Viscosity and the equation of state in high energy heavy-ion reactions
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2708
Viscous hydrodynamic calculations of high energy heavy-ion collisions (Nb-Nb and Au-Au) from 200 to 800 MeV/nucleon are presented. The resulting baryon rapidity distributions, the in-plane transverse momentum transfer (bounce-off), and the azimuthal dependence of the midrapidity particles (off-plane squeeze out) compare well with Plastic Ball data. We find that the considered observables are sensitive both to the nuclear equation of state and to the nuclear shear viscosity η. Transverse momentum distributions indicate a high shear viscosity (η≊60 MeV/fm2 c) in the compression zone, in agreement with nuclear matter estimates. The bulk viscosity ζ influences only the entropy production during the expansion stage; collective observables like flow and dN/dY do not depend strongly on ζ. The recently observed off-plane (φ=90°) squeeze-out, which is found in the triple-differential rapidity distribution, exhibits the strongest sensitivity to the nuclear equation of state. It is demonstrated that for very central collisions, b=1 fm, the squeeze-out is visible even in the double-differential cross section. This is experimentally accessible by studying azimuthally symmetric events, as confirmed recently by data of the European 4π detector collaboration at Gesellchaft für Schwerionforschung Darmstadt.Wolfram Schmidt; U. Katscher; Bèla M. Waldhauser; Joachim A. Maruhn; Horst Stöcker; Walter Greinerarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2708Wed, 24 May 2006 10:20:13 +0200Pion and thermal photon spectra as a possible signal for a phase transition
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2957
We calculate thermal photon and neutral pion spectra in ultrarelativistic heavy-ion collisions in the framework of three-fluid hydrodynamics. Both spectra are quite sensitive to the equation of state used. In particular, within our model, recent data for S + Au at 200 AGeV can only be understood if a scenario with a phase transition (possibly to a quark-gluon plasma) is assumed. Results for Au+Au at 11 AGeV and Pb + Pb at 160 AGeV are also presented.Adrian Dumitru; Ulrich Katscher; Joachim A. Maruhn; Horst Stöcker; Walter Greiner; Dirk-Hermann Rischkepreprinthttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2957Wed, 22 Feb 2006 16:50:36 +0100Bose stimulated pion production in relativistic nuclear collisions
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2952
We demonstrate the importance of the Bose-statistical effects for pion production in relativistic heavy-ion collisions. The evolution of the pion phase-space density in central collisions of ultrarelativistic nuclei is studied in a simple kinetic model taking into account the effect of Bose-simulated pion production by the NN collisions in a dense cloud of mesons.Igor N. Mishustin; Leonid M. Satarov; Joachim A. Maruhn; Horst Stöcker; Walter Greinerarticlehttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2952Wed, 15 Feb 2006 16:26:33 +0100Thermal photons as a measure for the rapidity dependence of the temperature
http://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2944
The rapidity distribution of thermal photons produced in Pb+Pb collisions at CERN-SPS energies is calculated within scaling and three- fluid hydrodynamics. It is shown that these scenarios lead to very different rapidity spectra. A measurement of the rapidity dependence of photon radiation can give cleaner insight into the reaction dynamics than pion spectra, especially into the rapidity dependence of the temperature.Adrian Dumitru; Ulrich Katscher; Joachim A. Maruhn; Horst Stöcker; Walter Greiner; Dirk-Hermann Rischkepreprinthttp://publikationen.stub.uni-frankfurt.de/frontdoor/index/index/docId/2944Fri, 10 Feb 2006 16:36:22 +0100