Production of meson molecules in ultra-peripheral heavy ion collisons

In this work we present a calculation of exotic charmonium production in ultra-peripheral collisions, in which the exotic state is explicitly treated as a meson molecule. Our formalism is general but we focus on the lightest possible exotic charmonium state: a D⁺ D⁻ molecular bound state. It was proposed some time ago and it has been object of experimental searches. Here we study the production of the open charm pair in the process γ γ → D⁺ D⁻. Then we use a prescription to project the free pair |D⁺ D⁻ onto a bound state at the amplitude level and compute the cross section of the process γ γ → B (where B is the bound state). Finally, we convolute this last cross section with the equivalent photon distributions coming from the projectile and target in an ultra-peripheral collision and find the A A → A A B cross section, which, for $Pb-Pb$ collisions at √sNN = 5.02 TeV, is of the order of 3 \, μ b.