Double -- photon exclusive processes with heavy quark -- heavy antiquark pairs in high-energy Pb-Pb collisions at LHC

TL;DR

This paper calculates the cross sections for exclusive heavy quark-antiquark pair production in ultrarelativistic Pb-Pb collisions at the LHC, focusing on photon-photon interactions and comparing different computational approaches.

Contribution

It provides the first detailed calculation of exclusive heavy quark pair production via photon-photon interactions at LHC energies, including multiple final states and realistic nuclear charge densities.

Findings

Cross sections are smaller than photon-pomeron diffractive mechanisms.

Cross sections are larger than pomeron-pomeron diffractive processes.

Different components contribute similarly to the total cross section.

Abstract

The cross section for exclusive heavy quark and heavy antiquark pair ($Q \bar Q$) production in peripheral ultrarelativistic heavy ion collisions is calculated for the LHC energy $\sqrt{s_{NN}}$ = 5.5 TeV. Here we consider only processes with photon--photon interactions and omit diffractive contributions. We present results in the impact parameter equivalent photon approximation (EPA) and compare some of them with results obtained by exact calculations of the Feynman diagrams in the momentum space. We include both $Q \bar Q$, $Q \bar Q g$ and $Q \bar Q q \bar q$ final states as well as photon single-resolved components. Realistic charge densities in nuclei were taken in the calculation. 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.