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Versungen und vertan? : Rückblicke auf 40 Jahre DDR-Literatur und Geschichtsschreibung der DDR-Literatur (1998)

Wolfgang Emmerich

1981 erschien eine erste Fassung meiner Kleinen Literaturgeschichte der DDR, eine zweite, stark erweiterte und bis an den Herbst 1988 heranreichende Ausgabe im Frühjahr 1989. Die seit dem Frühjahr 1996 vorliegende dritte Fassung zeigt, daß sich mein Blick auf vierzig und mehr Jahre DDR und DDR-Literatur nicht unbeträchtlich verändert hat. Anders als die (wenigen) Forscherkollegen, die sich nicht zu korrigieren brauchten, anders vor allem als die große Zahl derer, die sich nicht korrigieren wollten und schnurstracks zu einer neuen Tagesordnung übergingen, als ob nichts gewesen wäre, fand ich Anlaß zu einer ganzen Reihe von Korrekturen. Bei aller Kritik hatte ich dem Staat DDR und seinen offiziellen kulturellen Hervorbringungen immerhin einigen Kredit eingeräumt. Die Loyalitätsfalle Antifaschismus und die Sehnsucht nach einem wahren Sozialismus waren wohl die entscheidenden Gründe dafür. Sigmund Freud umreißt den therapeutischen Prozeß der Psychoanalyse bekanntlich mit dem Dreischritt 'Erinnern, Wiederholen und Durcharbeiten', und dazu gehören, wie man weiß, auch Mühen und Schmerzen. Mir schien es so, daß es unausweichlich sei - mit dem Motto von Freud - , den Weg von der Mythologisierung zur Historisierung der DDR-Literatur zu gehen. Die nachstehenden Blicke zurück - ohne Zorn, aber doch kritisch und mit je einer Prise Selbstironie und Trauer versehen, versuchen es.

The origin of transverse flow at the SPS (1998)

Marcus Bleicher Christian Spieles Christoph Ernst Lars Gerland Sven Soff Horst Stöcker Walter Greiner Steffen A. Bass

We study the transverse expansion in central Pb+Pb collisions at the CERN SPS. Strong collective motion of hadrons can be created. This flow is mainly due to meson baryon rescattering. It allows to study the angular distribution of intermediate mass meson baryon interactions.

Intermediate mass excess of dilepton production in heavy ion collisions at BEVALAC energies (1998)

Christoph Ernst Steffen A. Bass Mohamed Belkacem Horst Stöcker Walter Greiner

Dielectron mass spectra are examined for various nuclear reactions recently measured by the DLS collaboration. A detailed description is given of all dilepton channels included in the transport model UrQMD 1.0, i.e. Dalitz decays of π, η, ω, ή mesons and of the (1232) resonance, direct decays of vector mesons and pn bremsstrahlung. The microscopic calculations reproduce data for light systems fairly well, but tend to underestimate the data in pp at high energies and in pd at low energies. These conventional sources, however, cannot explain the recently reported enhancement for nucleus-nucleus collisions in the mass region 0.15GeV ≤ Me+e- ≤ 0.6GeV. Chiral scaling and ω meson broadening in the medium are investigated as a source of this mass excess. They also cannot explain the recent DLS data.

Nuclear shadowing effects on prompt photons at RHIC and LHC (1998)

Nils Hammon Adrian Dumitru Horst Stöcker Walter Greiner

The transverse momentum distribution of prompt photons coming from the very early phase of ultrarelativistic heavy ion collisions for the RHIC and LHC energies is calculated by means of perturbative QCD. We calculate the single photon cross section (A + B -> gamma + X) by taking into account the partonic sub processes q + q -> gamma + g and q + g -> gamma + q as well as the Bremsstrahlung corrections to those processes. We choose a lower momentum cut-off k0 = 2 GeV separating the soft physics from perturbative QCD. We compare the results for those primary collisions with the photons produced in reactions of the thermalized secondary particles, which are calculated within scaling hydrodynamics. The QCD processes are taken in leading order. Nuclear shadowing corrections, which alter the involved nuclear structure functions are explicitly taken into account and compared to unshadowed results. Employing the GRV parton distribution parametrizations we find that at RHIC prompt QCD-photons dominate over the thermal radiation down to transverse momenta kT ≈ 2 GeV. At LHC, however, thermal radiation from the QGP dominates for photon transverse momenta kT ≤ 5 GeV, if nuclear shadowing effects on prompt photon production are taken into account.

Relativistic transport theory for N, Delta and N*(1440) system (1998)

Guangjun Mao Ludwig Neise Horst Stöcker Walter Greiner

A self-consistent relativistic Boltzmann-Uehling-Uhlenbeck equation for the N (1440) resonance is developed based on an effective Lagrangian of baryons interacting through mesons. The equation is consistent with that of nucleon s and delta s which we derived before. Thus, we obtain a set of coupled equations for the N, Delta and N (1440) distribution functions. All the N (1440)-relevant in-medium two-body scattering cross sections within the N, Delta and N (1440) system are derived from the same effective Lagrangian in addition to the mean field and presented analytically. Medium effects on the cross sections are discussed.

Self-consistent relativistic quantum transport theory of hadronic matter : the coupled nucleon, delta and pion system (1998)

Guangjun Mao Ludwig Neise Horst Stöcker Walter Greiner

We derive the self-consistent relativistic quantum transport equation for the pion distribution function based on an effective Lagrangian of the QHD-II model. The closed time-path Green's function technique, the semi-classical, quasi-particle and Born approximation are employed in the derivation. Both the mean field and collision term are derived from the same Lagrangian and presented analytically. The dynamical equation for the pions is consistent with that for the nucleons and deltas which we developed before. Thus, we obtain a self-consistent relativistic transport model which describes the hadronic matter with N, Delta and pi degrees of freedom simultaneously. Within this approach, we investigate the medium effects on the pion dispersion relation as well as the pion absorption and pion production channels in cold nuclear matter. In contrast to the results of the non-relativistic model, the pion dispersion relation becomes harder at low momenta and softer at high momenta as compared to the free one. The theoretically predicted free pi N to Delta cross section is in agreement with the experimental data. Medium effects on the pi N to Delta cross section and momentum-dependent Delta-decay width are shown to be substantial.

Relativistic quantum transport theory of hadronic matter: the coupled nucleon, delta and pion system (1998)

Guangjun Mao Ludwig Neise Horst Stöcker Walter Greiner

We derive the relativistic quantum transport equation for the pion distribution function based on an effective Lagrangian of the QHD-II model. The closed time-path Green s function technique, the semi-classical, quasiparticle and Born approximation are employed in the derivation. Both the mean field and collision term are derived from the same Lagrangian and presented analytically. The dynamical equation for the pions is consistent with that for the nucleons and deltas which we developed before. Thus, we obtain a relativistic transport model which describes the hadronic matter with N,Delta and pi degrees of freedom simultaneously. Within this approach, we investigate the medium e ects on the pion dispersion relation as well as the pion absorption and pion production channels in cold nuclear matter. In contrast to the results of the non-relativistic model, the pion dispersion relation becomes harder at low momenta and softer at high momenta as compared to the free one, which is mainly caused by the relativistic kinetics. The theoretically predicted free pi*N -> Delta cross section is in agreement with the experimental data. Medium e ects on the pi*N -> Delta cross section and momentum-dependent Delta-decay width are shown to be substantial. PACS number(s): 24.10.Cn; 13.75.Cs; 21.65.+f; 25.70.-z

J/Psi production, chi polarization and color fluctuations (1998)

Lars Gerland Leonid Frankfurt Mark Strikman Horst Stöcker Walter Greiner

The hard contributions to the heavy quarkonium-nucleon cross sections are calculated based on the QCD factorization theorem and the nonrelativistic quarkonium model. We evaluate the nonperturbative part of these cross sections which dominates at psNN 20 GeV at the Cern Super Proton Synchrotron (SPS) and becomes a correction at psNN 6 TeV at the CERN Large Hadron Collider (LHC). J/psi production at the CERN SPS is well described by hard QCD, when the larger absorption cross sections of the states predicted by QCD are taken into account. We predict an A-dependent polarization of the states. The expansion of small wave packets is discussed.

Can momentum correlations proof kinetic equilibration in heavy ion collisions at 160/A-GeV? (1998)

Marcus Bleicher Mohamed Belkacem Christoph Ernst Henning Weber Lars Gerland Christian Spieles Steffen A. Bass Horst Stöcker Walter Greiner

We perform an event-by-event analysis of the transverse momentum distribution of final state particles in central Pb(160AGeV)+Pb collisions within a microscopic non-equilibrium transport model (UrQMD). Strong influence of rescattering is found. The extracted momentum distributions show less fluctuations in A+A collisions than in p+p reactions. This is in contrast to simplified p+p extrapolations and random walk models.

Supercooling of rapidly expanding quark-gluon plasma (1998)

Eugene E. Zabrodin Larissa V. Bravina László Pal Csernai Horst Stöcker Walter Greiner

We reexamine the scenario of homogeneous nucleation of the quark-gluon plasma produced in ultra-relativistic heavy ion collisions. A generalization of the standard nucleation theory to rapidly expanding system is proposed. The nucleation rate is derived via the new scaling parameter Z. It is shown that the size distribution of hadronic clusters plays an important role in the dynamics of the phase transition. The longitudinally expanding system is supercooled to about 3 6%, then it is reheated, and the hadronization is completed within 6 10 fm/c, i.e. 5 10 times faster than it was estimated earlier, in a strongly nonequilibrium way. PACS: 12.38.Mh; 12.39.Ba; 25.75.-q; 64.60.Qb

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