Coulomb breakup of neutron-rich isotopes of light nuclei

The effects of higher order multipole transitions, in particular, E2 and E1–E2 interference, in the Coulomb dissociation of neutron-rich nuclei ¹¹Be, ¹⁴B, ¹⁵C, and ¹⁹C on Pb targets at energies of 72, 86, 550, and 77 A MeV, respectively, within the framework of the eikonal-approximation approach are studied. The main steps involved in the derivation of the explicit expressions corresponding to dipole, quadrupole, and dipole-quadrupole-interference terms are outlined. The calculations reveal that the contribution of E2 transitions to the total cross section is finite but small, while that ofE1–E2 interference is nil.Nevertheless, the E1–E2 interference term introduces small distortions in the peak of the relative-energy spectrum. The calculated results are compared with the corresponding data and the comparison favors a value of 0.530 MeV as the ground-state binding energy of ¹⁹C. The text was submitted by the authors in English.     

Photon-photon luminosities in relativistic heavy ion collisions at LHC energies

Effective – luminosities are calculated for various realistic hadron collider scenarios. The main characteristics of photon-photon processes at relativistic heavy-ion colliders are established and compared to the corresponding –-luminosities ate ⁺-e ^– — and future photon linear colliders (PLC). Higher order corrections as well as inelastic processes are discussed. It is concluded that feasible high luminosity Ca–Ca collisions at the Large Hadron Collider (LHC) are an interesting option for – physics up to about 100 GeV – CM energy.     

The Ψ′ in the relativistic heavy ion collision

We have investigated the temperature influence on the hadronic decay width of Ψ′. Contrary to the divergence of the decay width ofρ-meson,π-meson at critical temperature as suggested in some papers, we find that the decay width of Ψ′ decreases with increasing temperature. Thus the leptonic decay can be used to measure the number of produced Ψ′ at finite temperature just as at zero temperature.     

Bremsstrahlung pair production in relativistic heavy ion collision

We calculate production of electron- and muon-pairs by the bremsstrahlung process in hadron collisions and compare it with the dominant two-photon process. Results for the total cross section are given for proton-proton and heavy-ion collisions at energies of the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). Received: 4 March 1997 / Revised version: 8 July 1997 / Published online: 20 February 1998     

Coulomb corrections to bremsstrahlung in the electric field of a heavy atom at high energies

We consider the differential and partially integrated cross sections for bremsstrahlung from high-energy electrons in an atomic field, with this field taken into account exactly. We use the semiclassical electron Green function and wavefunctions in an external electric field. It is shown that the Coulomb corrections to the differential cross section are very susceptible to screening. Nevertheless, the Coulomb corrections to the cross section summed over the final-electron states are independent of screening in the leading approximation in the small parameter 1/mr _scr (r _scr is the screening radius and m is the electron mass, ? = c = 1). We also consider bremsstrahlung from a finite-size electron beam on a heavy nucleus. The Coulomb corrections to the differential probability are also very susceptible to the beam shape, while the corrections to the probability integrated over momentum transfer are independent of it, apart from the trivial factor, which is the electron-beam density at zero impact parameter. For the Coulomb corrections to the bremsstrahlung spectrum, the next-to-leading terms with respect to the parameters mε (ε is the electron energy) and 1/mr _scr are obtained.     

γ-Spectroscopy of light neutron-rich nuclei after secondary reactions at relativistic energies

After the fragmentation reaction of ⁵⁰Ti on ⁹Be at 330 MeV/u, more than 30 neutron-rich isotopes from B to Ca were selected by the fragment separator FRS at GSI. Peripheral collisions with a secondary Pb target at relativistic energies were used to study the excited states of these isotopes. De-excitation γ-rays were detected with the Darmstadt-Heidelberg Crystal Ball spectrometer. The first results demonstrate the feasibility of in-beam γ-spectroscopy at relativistic energies.     

Calculation of relativistic effects in sub Coulomb heavy ion scattering

Relativistic corrections for the elastic scattering of heavy ions in the sub Coulomb regime are given. The case of two identical particles is treated especially. The deviation from the Rutherford (Mott) cross section is calculated by using the Todorov equation and the Darwin Hamiltonian, resp. It is shown, that both approches lead to the same results for small kinetic energies. Furthermore we discuss the applicability of the WKB method for calculating the phase shifts and the possibility of using a classical perturbative approach in the case of nonidentical particles.     

A QED description of relativistic Coulomb excitation in heavy ion collisions

A quantum electrodynamical treatment of Coulomb excitation in relativistic heavy ion collisions is presented. It is shown that a subtle interplay between quantum and relativistic kinematical effects induced by the nuclear recoil due to excitation generates a qualitatively different prediction (under certain kinematical conditions) from the corresponding prediction of conventional theories. The present formalism is applied to the clear fission problem and the results seem to solve the puzzle associated with this process for some time.     

Inelastic scattering of heavy ions from deformed light nuclei at near-barrier energies

Angular distributions have been measured at energies near the Coulomb barrier for the systems ¹⁸O + ²⁴Mg, ¹²C + ²⁸Si and ^{16, 18}O + ²⁸Si for elastic scattering and inelastic scattering to the first 2⁺ states in ¹⁸O, ²⁴Mg and ²⁸Si. Coupled-channel calculations were required in order to reproduce the details of the strong Coulomb-nuclear interference minima. However, a satisfactory account of the main features of the data was obtained in a first-order DWBA analysis and with the closed formalism of Frahn. With the exception of ¹⁸O, it was sufficient to assume equal charge and optical-potential deformation lengths.     

Simulation of first order confinement transition in relativistic heavy ion collision

We have carried out numerical simulation of first order phase transition in 2+1 dimensions to study the formation and evolution of Z(3) domain walls in relativistic Heavy Ion Collision using the effective potential proposed by Pisarski for QCD where Polyakov loop is the order parameter of the weak first order phase transition. Bubbles of the QGP phase are randomly nucleated on the lattice, which grow and coalesce. The spontaneous breaking of Z(3) symmetry in QGP phase gives rise to domain walls and topological strings. We discuss P _T enhancement due to reflection of quarks from the collapsing domain walls. We also discuss enhancement of doubly strange and triply strange hadrons due to larger concentration of s quarks inside collapsing wall. The decay of the domain walls when temperature drops below T _c results in the fluctuations of energy density.     

Study of deuteron breakup in light targets at intermediate energies

Reaction cross-sections and proton removal cross-sections in deuteron-induced reactions with carbon and beryllium targets are studied at intermediate energies. The cross-sections calculated in eikonal approximation show a good agreement with experimental data. The sensitivity of the cross-sections to the target structure, the nucleon-target interaction potential, and the spatial distribution of nucleons in the deuteron is discussed. Received: 30 May 2001 / Accepted: 2 October 2001     

Production of secondaries in relativistic nuclei collisions at high energies

Using the multiple-scattering theory and quark-gluon string model, the averaged and central collisions between high-energy nuclei are studied. Production of light flavour hadrons as well as charmed and beauty mesons and baryons is considered. We present predictions for mean multiplicities of secondaries, inclusive spectra and distributions over multiplicity for the case of Au?Au collisions with energy 100 GeV per nucleon in every beam.     

Peculiarities of deuteron splitting by the Coulomb field of heavy nuclei

It is shown that the (d, pf) reaction occurs through two channels. The second channel is related to the deuteron splitting in the Coulomb field of the nucleus and the formation of a singlet deuteron with a kinetic energy lower than the incident-deuteron energy by 2.3 MeV, sizes exceeding > a _np, and an isospin equal to 1. The interaction of a singlet deuteron with the initial nucleus leads to occupation of the shape isomer states.     

Further studies of large collision residues in relativistic heavy-ion reactions with heavy nuclei

Target residue mass and charge distributions have been measured radiochemically for the reaction of 25.2 GeV ¹²C ions with Au and Pb. Enhanced product yields for A = 140?170 are found that are not present in reactions of Pb with GeV protons. The shape of the mass distribution in this region is used to define a pre-equilibrium product mass distribution.     

Mean field model for relativistic heavy ion collisions

We take up a relativistic mean-field model consisting out of nucleons coupled to a scalar and a vector meson. We solve the corresponding time-dependent mean-field equations on a three-dimensional grid. Results for¹⁶O +¹⁶O scattering at various energies and various impact parameters show significant differences with conventional TDHF calculations. We see sidewards collective flow similar as in fluid dynamics and in experiment. We observe complete spallation and remarked oscillations of the meson fields.     

Emission of helium nuclei in heavy ion interactions at energies ≧ 100 MeV/nucleon

The energy and angular distributions of helium particles emitted in interactions between nuclei in the cosmic radiation and nuclei in photoemulsions at energies ≧ 100 MeV/nucleon have been studied. The data obtained is impossible to interpret on the basis of a statistical decay of excited nuclei. For example, it is found that more than 28% of the helium nuclei are emitted in processes different from simple evaporation. The differential energy distribution of the helium nuclei in the energy interval (40–200) MeV can be represented by the relationN(E)dE=constE ^?a dE, wherea≈1.2. The large spread in angles and energies of the fast helium particles emitted in heavy ion interactions can to a certain degree be understood, if it is assumed that interactions between nucleons and clusters of nucleons occur.     

Freeze-out in relativistic heavy ion collisions at SPS

The freeze-out conditions in the light (S+S) and heavy (Pb+Pb) colliding systems at 160 AGeV/c are analyzed within the microscopic Quark Gluon String Model (QGSM). Even for the most heavy systems particle emission takes place from the whole space-time domain available for the system evolution, but not from the thin “freeze-out hypersurface”, adopted in fluid dynamical models. Pions are continuously emitted from the whole volume of the reaction and reflect the main trends of the system evolution. Nucleons in Pb+Pb collisions initially come from the surface region. For both reactions there is a separation of the elastic and inelastic freeze-out.