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Comment on "Exactly central heavy-ion collisions by nuclear hydrodynamics" (1981)

László Pal Csernai Horst Stöcker

Problems arising in viscous nuclear fluid dynamical models of high-energy heavy-ion collisions are discussed. The importance of an accurate treatment of the transport properties of the hot and dense nuclear matter is pointed out.

Macroscopic nucleon-nucleon correlations caused by the bounce-off process in energetic collisions of heavy nuclei (1981)

László Pal Csernai Walter Greiner Horst Stöcker Isao Tanihata Shoji Nagamiya Jörn Knoll

Two-particle correlation data are presented for the reaction Ar (800 MeV/ nucleon) + Pb. The experimental results are analyzed in the nuclear fluid dynamical and in a linear cascade model. We demonstrate that the collective hydrodynamical correlations dominate the measured two-particle correlation function for the heavy system studied. We discuss the transition from the early stages of the reaction which are governed by few nucleon correlations, to the later stages with their macroscopic flow which can only be reached using heavy colliding systems. The sensitivity of the correlation data on the underlying compressional dissipative processes is analyzed.

Jets of nuclear matter from high energy heavy ion collisions (1981)

Horst Stöcker László Pal Csernai Gerhard Graebner Gerd Buchwald Hans Kruse R. Y. Cusson Joachim A. Maruhn Walter Greiner

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.

Measurement of complex fragments and clues to the entropy production from 42-137-MeV/nucleon Ar + Au (1983)

B. V. Jacak G. D. Westfall C. K. Gelbke L.H. Harwood W. G. Lynch D.K. Scott Horst Stöcker M.B. Tsang T. J. M. Symons

Intermediate-rapidity fragments with A=1-14 emitted from 42-137-MeV/nucleon Ar + Au have been measured. Evidence is presented that these fragments arise from a common moving source. Entropy values are extracted from the mass distributions by use of quantum statistical and Hauser-Feshbach theories. The extracted entropy values of S/A≈2-2.4 are much smaller than the values expected from measured deuteron-to-proton ratios, but are still considerably higher than theoretically predicted values.

Viscous fluid dynamical calculation of the reaction 12C(85 MeV/nucleon) + 197Au (1983)

Gerd Buchwald Gerhard Graebner J. Theis Joachim A. Maruhn Walter Greiner Horst Stöcker

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.

Time-dependent Hartree-Fock studies of superheavy molecules (1983)

M. R. Strayer R. Y. Cusson Horst Stöcker Joachim A. Maruhn Walter Greiner

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.

Light particle spectra from 35 MeV/nucleon 12C-induced reactions on 197Au (1984)

G. D. Westfall Z.K. Koenig B. V. Jacak L.M. Harwood G.M. Crawley M.W. Curtin C. K. Gelbke B. Hasselquist W. G. Lynch A.D. Panagiotou D.K. Scott Horst Stöcker M.B. Tsang

Energy spectra for p, d, t, 3He, 4He, and 6He from the reaction 12C+197Au at 35 MeV/nucleon are presented. A common intermediate rapidity source is identified using a moving source fit to the spectra that yields cross sections which are compared to analogous data at other bombarding energies and to several different models. The excitation function of the composite to proton ratios is compared with quantum statistical, hydrodynamic, and thermal models.

Microscopic calculations of collective flow probing the short-range nature of the nuclear force (1984)

Joseph J. Molitoris J. B. Hoffer Hans Kruse Horst Stöcker

Collisions between two nuclei have been modeled by numerical solution of classical approximations to the equations of motion of the constituent nucleons. For the reaction Nb(400 MeV/u)+Nb, a correlated sidewards emission of nucleons is observed. This is attributed to the repulsive short-range component of the nucleon-nucleon potential. A strong dependence of the flow angle on the impact parameter is observed, in accord with recent experimental results.

Rapidity dependence of entropy production in proton- and nucleus-induced reactions on heavy nuclei (1984)

B. V. Jacak Horst Stöcker G. D. Westfall

The entropy of hot nuclear systems is deduced from the mass distribution of fragments emitted from high energy proton- and nucleus-induced reactions via a quantum statistical model. It is found that the entropy per baryon, S/A, of intermediate rapidity ("participant") fragments is higher than the entropy of target rapidity ("spectator") fragments. The spectator fragments exhibit S/A values of ≅ 1.8 independent of the projectile energy from 30 MeV/nucleon up to 350 GeV. This value of the entropy coincides with the entropy at which nuclear matter becomes unbound.

Kinetic energy flow in Nb(400 A MeV) + Nb: evidence for hydrodynamic compression of nuclear matter (1984)

Gerd Buchwald Gerhard Graebner J. Theis Joachim A. Maruhn Walter Greiner Horst Stöcker

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.

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