Collisions Of Heavy Nuclei Research Articles

Additive quark model of multiparticle production and nucleus-nucleus collisions at high energies

An extension of the additive quark model of hadron-hadron and hadron-nucleus collisions to the case of nucleus-nucleus interactions at very high energies is presented. Estimates are given of the number of wounded and spectator quarks, and of the number of colored strings spanned between interacting nuclei. These estimates indicate the possibility of a rich structure of the spectra of produced particles and an increase (relative to the nucleon-nucleon case) of multiplicities up to a factor \ensuremath{\sim}50 in collisions of heavy nuclei.

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

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 and dissipative processes is analyzed.

Microscopic calculation of friction coefficients for use in heavy-ion reaction

A microscopic calculation has been done for the friction coefficient for use in the deep-inelastic collision of heavy nuclei. We adopted the formalism of the linear response theory as a basis and used the adiabatic base of the two-center shell model. Several reaction channels with the total mass numbers of 236 and 260 systems were investigated. The friction coefficients for the radial and deforming motions including the coupling term were calculated as a function of the distance between two nuclei and deformation of the two nuclei for each channel. The general feature of the friction coefficient, its strength and form factor, was clarified in this model and comparison with the results of other models were done. It was found that our model gives a physically plausible value for the friction coefficient as a whole.

Medium energy collisions of heavy nuclei in the three-dimensional nuclear fluid dynamical-(NFD) and Time-Dependent Hartree-Fock (TDHF) models

We study heavy ion collisions at bombarding energiesE LAB/n∼ 20–200 MeV within the three-dimensional NFD- and TDHF-models. A surprisingly good agreement between the results of the different models is found: The comparison phenomena occuring at these bombarding energies are quantitatively similar as a function of the bombarding energy as well as for various impact parameters. The formation of abnormal superdense nuclear matter (“density isomers”) is investigated in a schematic model for the nuclear equation of state. Again we find very similar results in the two models. Density isomers can be formed in high energy heavy ion collisions above a critical bombarding energy and below a critical impact parameter, which both depend on the details of the nuclear equation of state. Cross sections for the formation of density isomers are presented. An experiment for the detection of abnormal nuclear matter in fast, central heavy ion collisions is proposed.

Evidence for a Soft Nuclear-Matter Equation of State

The entropy of the fireball formed in central collisions of heavy nuclei at center-of-mass kinetic energies of a few hundred MeV per nucleon is estimated from the ratio of deuterons to protons at large transverse momentum. The observed paucity of deuterons suggests that strong attractive forces are present in hot, dense nuclear matter, or that degrees of freedom beyond the nucleon and pion may already be realized at an excitation energy of 100 MeV per baryon.

Three-dimensional calculations on the formation of density isomers in high energy heavy ion collisions

A three dimensional fluid dynamical model is used to investigate the possibility of forming superdense abnormal nuclear matter (“density isomers”) in fast collisions of heavy nuclei, the dependence of the formation process on the bombarding energy and on the impact parameter. An experiment for the detection of such phase transitions in nuclear matter is suggested.

Evidence for a Blast Wave from Compressed Nuclear Matter

Central collisions of heavy nuclei at c.m. kinetic energies of a few hundred MeV per nucleon produce fireballs of hot, dense nuclear matter. Each fireball explodes, producing a blast wave of nucleons and pions. Several features of the observed cross sections for pions and protons from Ne on Na F at 0.8 GeV/nucleon (lab) are explained by the blast wave, but contradict earlier, purely thermal models. The available energy is equally divided between translational energy of the blast, and thermal motion of the particles in the exploding matter.

Time-dependent Hartree-Fock calculations using separable three-dimensional wavefunctions

Time-dependent Hartree-Fock calculations are presented using an approximation which decomposes the fully three-dimensional equations into a set of coupled equations in one and two dimensions. The approximation is tested for the alpha + alpha collision at a laboratory energy of 75.2 MeV and the extension of the technique to collisions of light and heavy nuclei is discussed.

High-Energy Collisions of Heavy Nuclei

The profile function for the collision of two heavy nuclei is calculated. In principle, the method used sums all contributing diagrams. The single-particle inclusive distribution is predicted for very-high-energy collisions.

Search for the "Abnormal Nuclear State" Heavy, A > 200, Ion Acceleration in the AGS

Recent theoretical work speculates on the existence of abnormal states of matter which could possibly be created as a result of collisions of superenergetic heavy nuclei. For this reason the possibility of acceleration of heavy ions with mass number A > 200 to kinetic energies of 1 < Tn < 10 GeV/nucleon has been studied and found to be feasible without modification of the AGS vacuum and rf systems by using a fast cycling synchrotron as a booster ring. This booster is required in order to obtain the fully stripped ion state, since partially stripped heavy ion acceleration in a slow rise time accelerator is impractical because of extreme vacuum requirements. The fast cycling feature of the booster is essential in reducing transmission losses associated with electron capture or loss during acceleration and beneficial in increasing the final beam intensity.

Spontaneous production of positrons in collisions of heavy nuclei

Spontaneous production of positrons in collisions of heavy nuclei

Angular distribution of jets produced by heavy primary cosmic-ray nuclei

A statistical method is developed for analyzing the angular distribution of meson jets produced by heavy primary cosmic-ray nuclei, enabling detection and elimination of the proton jet due to evaporation of the residual incident nucleus. The procedure is applied to 50 high-energy collisions of heavy primary nuclei. It is shown that a significant fraction of the heavy primaries produce bi-modal meson jets consistent with the two-centre model.

Nuclear Interactions and Mean Free Paths of Protons, Neutrons, and Alpha Particles at Energies Around 250 Bev/Nucleon

Nuclear interactions of protons, neutrons, $\ensuremath{\alpha}$ particles, and heavier nuclei of average energy 250 Bev/nuc were studied in nuclear emulsion. The source of these particles were fragmentations of heavy primary nuclei of the cosmic radiation. Their energy was determined from multiple scattering measurements. The interaction mean free path for protons is 41\ifmmode\pm\else\textpm\fi{}10 cm, for $\ensuremath{\alpha}$ particles 27\ifmmode\pm\else\textpm\fi{}7 cm. The mean free path shows no significant change compared with measurements at lower energies. The mean number of shower particles $〈{n}_{s}〉$ depends appreciably on the mass of the target nucleus. Our best estimate for nucleon-nucleon collisions at 250 Bev is $〈{n}_{s}〉=8.8\ifmmode\pm\else\textpm\fi{}1.9$. A detailed comparison of the estimate of the primary energy obtained from the angular distribution of shower particles with the true primary energy is carried out. The angular distribution of the shower particles will, in an individual case, give a quite unreliable value for the primary energy. In the average, the angular distribution method will over-estimate the true primary energy by a factor of 1.3 for interactions with a number of heavy prongs ${N}_{h}\ensuremath{\le}5$. If ${N}_{h}g5$, the angular distribution will underestimate the true energy in the average by a factor of 1.8. The angular distributions can be transformed into a system in which they are symmetric. This is even true for collisions with heavy target nuclei (${N}_{h}g5$). The results for alpha particle and heavy nucleus collisions are quite similar.The inelasticity for the proton and neutron interactions shows large fluctuations for individual events. It depends weakly on the number of shower particles and on the mass of the target nucleus. Its mean value is 50%. The mean value for the alpha-particle collisions is 22%.

The Heavy Nuclei of the Primary Cosmic Radiation

The atmospheric absorption of the flux of nuclei of charge \ensuremath{\ge}10 has been obtained at $\ensuremath{\lambda}=55$ N from a combination of flux measurements at different altitudes and at different zenith angles. The absorption, together with the collision cross section, gives an energy spectrum consistent with the one measured by stopping particles and the latitude effect. The cross section for collision of heavy nuclei is about three-fourths of the geometric cross section. The energy spectrum can be represented by $\mathrm{NE}&gt;{E}_{0}\ensuremath{\propto}\frac{1}{E_{0}^{\ensuremath{\gamma}}}$, where $\ensuremath{\gamma}$ is 0.5 for energies above 0.8 Bev/nucleon. $N$ is the number of nuclei with an energy greater than ${E}_{0}$ per nucleon. The flux measured at $\ensuremath{\lambda}=30$ N gives an exponent $\ensuremath{\gamma}=0.5$. At energies below about 0.75 Bev/nucleon the spectrum seems to get steeper. The flux of heavy nuclei measured on two night flights shows no significant difference from the day flux. Solar activity resulting in flares of importance 1 and 2 shows no measurable correlation with flux of heavy nuclei.