Impact-parameter dependence of the total probability for electromagnetic electron-positron pair production in relativistic heavy-ion collisions

Abstract

Effective γ-γ 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 γ-γ-luminosities at e + -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 γ-γ physics up to about 100 GeV γ-γ CM energy. 25.75.+r,13.40.-f Typeset using REVT E X 1

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

“…It was found that the total cross section for electron-positron pair production (given by a full QED calculation in lowest order [17] or alternatively by the approximate analytic expression of Racah [18], which coincide within the numerical accuracy of the calculations) is only reproduced with a cutoff chosen around m e . On the other hand it was also found that neither a choice of m e nor of R A is able to reproduce the total impact parameter dependent probability P͑b͒ at impact parameter smaller than the Compton wavelength c = 386 fm from an exact QED calculation [1]. For a discussion about the choice of the cutoff parameter see, e.g., Ref.…”

“…At impact parameter of the order of twice the nuclear radius, but still larger than this, so that the two ions do not interact hadronically with each other (that is, the regime of the socalled "ultraperipheral collisions" UPC), the total pair production multiplicity is found to be about 1.5 for Au-Au collisions at the Relativistic Heavy Ion Collider RHIC and about 3.9 for Pb-Pb collisions at the LHC. These results are based on a lowest order QED calculation [1] and one might suspect that at these small impact parameters the strong fields of the two ions do lead to higher order corrections.…”

Structure of the Coulomb and unitarity corrections to the cross section ofe+e−pair production in ultrarelativistic nuclear collisions

“…1) from the numerical results in [15] for the case γ = 3400. It follows from (16) that the asymptotic form of the function F (x) at x ≫ 1 reads…”

“…(15) is widely cited and used in many papers (see, e.g., Refs. [11,12,15,17,18,19,20,21]). Now we show that Eq.…”

“…For a few particular values of γ the function W 0 (ρ) was calculated numerically in [15,16] around mρ ∼ 1 . In [3], for mρ ≫ 1, this function was approximated by a simple expressioñ…”