D. Trautmann

Coherent γγ and γA interactions in very peripheral collisions at relativistic ion colliders

Abstract Due to coherence, there are strong electromagnetic fields of short duration in very peripheral collisions. They give rise to photon–photon and photon–nucleus collisions with a high flux up to an invariant mass region hitherto unexplored experimentally. After a general survey of the field equivalent photon numbers and photon–photon luminosities, especially for relativistic heavy ion collisions, are discussed. Special care needs to be taken to include the effects of the strong interaction and nuclear size in this case. Photon–photon and photon–hadron physics at various invariant mass scales are then discussed. The maximum equivalent photon energy in the lab-system (collider frame) are typically of the order of 3 GeV for RHIC and 100 GeV for LHC. Diffractive processes are an important background process. Lepton pair, especially electron–positron pair production is copious. Due to the strong fields there will be new phenomena, like multiple e + e − pair production. The experimental techniques to select γγ -processes are finally discussed together with important background processes.

Fragmentation processes in nuclear reactions

Abstract Fragmentation processes in nuclear collisions are reviewed. The main emphasis is put on light ion breakup at nonrelativistic energies. The post- and prior-form DWBA theories are discussed. The post-form DWBA, appropriate for the “spectator breakup” describes elastic as well as inelastic breakup modes. This theory can also account for the stripping to unbound states. The theoretical models are compared to typical experimental results to illustrate the various possible mechanisms. It is discussed, how breakup reactions can be used to study high-lying single particle strength in the continuum; how they can yield information about momentum distributions of fragments in the nucleus.

Photon-photon physics in very peripheral collisions of relativistic heavy ions

In central collisions at relativistic heavy ion colliders such as the Relativistic Heavy Ion Collider (RHIC), Brookhaven and the Large Hadron Collider (LHC) (in its heavy ion mode) at CERN, Geneva, one aims at detecting a new form of hadronic matter - the quark gluon plasma. It is the purpose of this review to discuss a complementary aspect of these collisions, the very peripheral ones. Owing to coherence, there are strong electromagnetic fields of short duration in such collisions. They give rise to photon-photon and photon-nucleus collisions with high flux up to an invariant mass region hitherto unexplored experimentally. After a general survey photon-photon luminosities in relativistic heavy ion collisions are discussed. Special care is taken to include the effects of strong interactions and nuclear size. Then photon-photon physics at various -invariant mass scales is discussed. The region of several GeV, relevant for RHIC is dominated by quantum chronodynamics phenomena (meson and vector meson pair production). Invariant masses of up to about 100 GeV can be reached at LHC, and the potential for new physics is discussed. Photonuclear reactions and other important background effects, especially diffractive processes are also discussed. A special chapter is devoted to lepton-pair production, especially electron-positron pair production; owing to the strong fields new phenomena, especially multiple pair production, will occur there.

On the rms radius of the deuteron

Abstract We use the world data on electron-deuteron elastic scattering to determine the deuteron structure functions and the charge rms radius. Coulomb distortion is included using second-Born approximation. We find a radius of 2.130 ± 0.003 ± 0.009 fm (±stat., ±syst.), which agrees with the information obtained from nucleon-nucleon scattering and from optical isotope shifts.

Electromagnetic dissociation as a tool for nuclear structure and astrophysics

Coulomb dissociation is an especially simple and important reaction mechanism. Since the perturbation due to the electric field of the nucleus is exactly known, firm conclusions can be drawn from such measurements. Electromagnetic matrix elements and astrophysical S-factors for radiative capture processes can be extracted from experiments. We describe the basic theory, new results concerning higher order effects in the dissociation of neutron halo nuclei, and briefly review the experimental results obtained up to now. Some new applications of Coulomb dissociation for nuclear astrophysics and nuclear structure physics are discussed.

Supermassive neutrino stars and galactic nuclei

Abstract The characteristics of supermassive ‘stars’ consisting of self-gravitating degenerate neutrino (or neutralino) matter are studied with particular emphasis on fermion masses around 17 keV/ c 2 . Such compact dark objects could be as massive as 10 9.5 to 1o 6.5 solar masses, with radii of about one to ten light days; they might thus mimic phenomena that are expected around the supermassive black holes recently purported at the centres of some galaxies and quasi-stellar objects.

Recoil effects in atomic inner shell ionization

Abstract Recoil effects in inner shell ionization are studied in the semiclassical model. They can be taken into account by a modified form factor. It is shown that recoil effects are of minor importance for monopole transitions, whereas for dipole transitions they are in general important. Calculations of inner shell ionization probabilities for light ion induced reactions are performed and compared with experiments where good agreement is found. It is seen that recoil effects show up especially at backward angles for double differential cross sections.

Multiple electromagnetic electron-positron pair production in relativistic heavy-ion collisions

We calculate the cross sections for the production of one and more electron-positron pairs due to the strong electromagnetic fields in relativistic heavy-ion collisions. We derive the N-pair amplitude using the generating functional of fermions in an external field and the path-integral formalism. The N-pair production probability is found to be an approximate Poisson distribution. We calculate total cross sections for the production of one pair in lowest order, including corrections from the Poisson distribution up to third order. Furthermore, we calculate cross sections for the production of up to five pairs including corrections from the Poisson distribution. {copyright} {ital 1997} {ital The American Physical Society}

Accurate calculation of inner-shell ionization

Abstract Inner-shell ionization is formulated in the semiclassical approximation, starting from a fully quantal approach. Classical trajectories in a screened Coulomb potential are used and the electron in the initial and final states are described by relativistic Hartree-Fock-Slater wave functions. Binding energy corrections due to the projectile field are applied. The agreement of the theoretical calculations with the rather detailed experiments (total cross sections, electron spectra, alignment) is generally very good.

Multiphoton Exchange Processes in Ultraperipheral Relativistic Heavy Ion Collisions

The very strong electromagnetic fields present in ultraperipheral relativistic heavy-ion collisions lead to important higher-order effects of the electromagnetic interaction. These multi-photon exchange processes are studied using perturbation theory and the sudden or Glauber approximation. In many important cases, the multi-photon amplitudes factorize into independent single-photon amplitudes. These amplitudes have a common impact parameter vector, which induces correlations between the amplitudes. Impact-parameter dependent equivalent-photon spectra for simultaneous excitation are calculated, as well as, impact-parameter dependent γγ-luminosities. Excitations, like the multi-phonon giant dipole resonances, vector meson production and multiple e+e−-pair production can be treated analytically in a bosonic model, analogous to the emission of soft photons in QED.