Double-scattering mechanism in the exclusive AA →AAρ0ρ0 reaction in ultrarelativistic collisions

We calculate, for the first time, differential distributions for double-ρ⁰-meson production in exclusive ultraperipheral, ultrarelativistic collisions via a double-scattering mechanism. The calculations are done in impact parameter space. The cross section for γ_{A →ρ⁰A is parametrized based on an existing calculation. Smearing of ρ⁰ masses is taken into account. The results of our calculations are compared at the Relativistic Heavy Ion Collider (RHIC) energy to the contribution of the two-photon mechanism discussed previously in the literature. The cross section for the double-scattering mechanism is found to be an order of magnitude larger at Mρρ}< 2 GeV and more than two orders of magnitude at M_ρρ> 3 GeV, than that for the photon-photon mechanism. Compared to the two-photon mechanism, the double-scattering mechanism populates somewhat larger ρ⁰ρ⁰ invariant masses and larger rapidity distances between the two ρ⁰ mesons and gives a significant contribution to the AA →AAπ⁺π^-π⁺π^- reaction. Some observables related to charged pions are presented too. We compare the results of our calculation with the STAR Collaboration results on four-charged-pion production. While the shape in invariant mass of the four-pion system is very similar to the measured one, the predicted cross section constitutes only 20% of the measured one. We discuss a possibility of identifying the double scattering mechanism at the Large Hadron Collider (LHC).