Exclusive production of lepton, quark and meson pairs in peripheral ultrarelativistic heavy ion collisions

Abstract

We discuss exclusive production of lepton-antilepton, quark-antiquark, ππ and ρ 0 ρ 0 pairs in ultraperipheral, ultrarelativistic heavy-ion collisions.The cross sections for exclusive production of pairs of particles is calculated in Equivalent Photon Approximation (EPA). Realistic (Fourier transform of charge density) charge form factors of nuclei are used and the corresponding results are compared with the cross sections calculated with monopole form factor used in the literature. Absorption effects are discussed and quantified. The cross sections obtained with realistic form factors are significantly smaller than those obtained with the monopole form factors.The cross section for exclusive µ + µ − production in nucleus -nucleus collisions are calculated and some differential distributions are shown. The effect of absorption is bigger for large muon rapidities and/or large muon transverse momenta. We present predictions for LHC.We calculate cross section for exclusive production of π + π − and π 0 π 0 pairs. The elementary process γγ → ππ is discussed in detail. We concentrate on high-pt processes. We consider pQCD Brodsky-Lepage processes or alternatively hand-bag mechanism. The nuclear cross section is calculated within b-space EPA for RHIC and LHC.Similar analysis is performed for ρ 0 ρ 0 production, where the elementary cross section is less known. Our analysis includes a close-to-threshold enhancement of the cross section. The cross section for the low-energy phenomenon is parametrized and the high-energy cross section is calculated in a simple Regge model. Predictions for heavy ion collisions are presented.The cross section for exclusive heavy quark and heavy antiquark pair (QQ) production in heavy ion collisions is calculated for the LHC energy √ sNN = 5.5 TeV. Here we consider only processes with photon-photon interactions and omit diffractive contributions. We include both QQ, QQg and QQqq final states as well as photon singleresolved components. The different components give contributions of the same order of magnitude to the nuclear cross section. The cross sections found here are smaller than those for the diffractive photon-pomeron mechanism and larger than diffractive pomeron-pomeron discussed in the literature.

Multiple scattering production of lepton-pairs in ultraperipheral heavy-ion collisions

“…Our result is higher than the experimental result and STARLIGHT calculation. Similar calculations have been done by using EPA method and the results can be found in references [24,25,26,27,28,29,30,31].…”

Multiple-scattering production of lepton pairs in ultraperipheral heavy-ion collisions

“…Similar calculations have been done by using EPA method and the results can be found in Refs. [23][24][25][26][27][28][29][30].…”