Speaker
Description
We study the $\gamma\gamma \to \tau^+\tau^-$ process in Pb--Pb ultraperipheral collisions, including the full spin information of the $\tau^+\tau^-$ system. We present predictions for the corresponding cross sections and spin correlations at next-to-leading-order electroweak accuracy, and find that the electroweak correction increases the total cross section by about nine per mille at the benchmark center-of-mass energies $\sqrt{s_{NN}}=5.02$, $5.36$, and $5.52~\mathrm{TeV}$, while its impact on the spin-correlation observables considered here is numerically small. In addition, we use the predicted spin correlations to investigate quantum entanglement in the $\tau^+\tau^-$ system produced in the $\gamma\gamma \to \tau^+\tau^-$ process. Our results indicate the presence of a genuinely entangled configuration near the $\tau^+\tau^-$ invariant-mass threshold.