Particle emission following Coulomb excitation in ultrarelativistic heavy-ion collisions

Abstract

We study nuclear reactions induced by virtual photons associated with Lorentz-boosted Coulomb fields of ultrarelativistic heavy ions. Evaporation, fission and multifragmentation mechanisms are included in a new RELDIS code, which describes the deexcitation of residual nuclei formed after single and double photon absorption in peripheral heavy-ion collisions. Partial cross sections for different dissociation channels, including the multiple neutron emission ones, are calculated and compared with data when available. Rapidity and transverse momentum distributions of nucleons, nuclear fragments and pions, produced electromagnetically, are also calculated. These results provide important information for designing large-rapidity detectors and zero-degree calorimeters at RHIC and LHC. The electromagnetic dissociation of nuclei imposes some constrains on the investigation of exotic particle production in γγ fusion reactions. 25.70.De, 24.10.Lx PACS

Production of QED pairs at small impact parameter in relativistic heavy ion collisions

“…(5). Of course one needs then to include in addition the different decay channels into one, two, etc., neutrons [26][27][28], as well as, the fact that the probability for GDR excitation is already quite large (about 0.5 for b min ) so that multiphoton excitation mechanisms need to be included as well. Assuming a Poisson distribution for the different (independent) excitation processes, one would need to replace P GDR ͑b͒ then with [24] P A→A *͑b͒ = 1 − exp͓P GDR ͑b͔͒.…”

Inclusive meson production in peripheral collisions of ultrarelativistic heavy ions

“…[11], the contribution to pion production from the double photon absorption is less then 10% for heavy ions with γ ≫ 100. Since the contribution from the third and fourth order processes are expected to be even lower, these processes can be safely disregarded for the ultrarelativistic energies.…”

“…[18], [10,11]. Formally we use 1 TeV as the upper limit for the equivalent photon energy in the γA process.…”

“…The electromagnetic collision events are less violent then the collisions with nuclear interactions. Thus the average particle multiplicities are essentially lower [10,11] and the main part of nucleons and mesons is produced in the regions of projectile and target fragmentation, very far from the mid-rapidity region.…”

“…[17] when the colliding nuclei remain intact. Different characteristics of pion production by the equivalent photons are calculated by the RELDIS code [11] based on the extended model of photonuclear reactions [18]. The FRITIOF Monte Carlo event generator, version 7.1 [19] is used to study the properties of grazing nuclear collisions.…”