Exclusive production of rho^0 rho^0 pairs in gamma-gamma collisions at RHIC

TL;DR

This paper calculates the cross section for exclusive production of rho^0 rho^0 pairs in ultrarelativistic heavy-ion collisions at RHIC, emphasizing the importance of realistic nuclear charge densities and low-energy photon interactions.

Contribution

It provides a detailed calculation of the nuclear photon-photon cross section for rho^0 rho^0 production, incorporating realistic flux factors and the VDM-Regge model, with implications for experimental measurements.

Findings

Cross sections are sensitive to low-energy gamma-gamma interactions.

Realistic charge densities significantly affect cross section estimates.

Large nuclear cross sections suggest measurable signals at RHIC.

Abstract

We discuss exclusive electromagnetic production of two neutral $\rho$ mesons in coherent photon-photon processes in ultrarelativistic heavy-ion collisions. The cross section is calculated in the equivalent photon approximation (EPA). Both uncertainties of the flux factors and photon-photon cross sections are discussed in details. We show that inclusion of precise charge densities in nuclei is essential for realistic evaluations of the nuclear photon-photon cross sections. We find that the cross section, especially with realistic flux factors, is sensitive to low energy in the subsystem $\gamma \gamma \to \rho^0 \rho^0$. The experimental data for the $\gamma \gamma \to \rho^0 \rho^0$ cross section extracted from $e^+ e^-$ collisions are parametrized and used to estimate the nucleus-nucleus cross section. In addition, we include vector-dominance-model(VDM)--Regge contribution which becomes important at large photon-photon energy. Large nuclear cross sections are obtained. We discuss a possibility of focusing on the large-energy component. We find that both $\rho^0$ mesons are produced predominantly at midrapidities and could be measured by the STAR collaboration at RHIC.