New Results for Ultraperipheral Heavy Ion Collisions.

We discuss diphoton semi(exclusive) production in ultraperipheral PbPb collisions at energy of ys_NN = 5.5 TeV (LHC). The nuclear calculations are based on equivalent photon approximation in the impact parameter space. The cross sections for elementary γγ → yy subprocess are calculated including three different mechanisms: box diagrams with leptons and quarks in the loops, a VDM-Regge contribution with virtual intermediate hadronic excitations of the photons and the two-gluon exchange contribution (formally three-loops). We got relatively high cross sections in PbPb collisions. This opens a possibility to study the γγ → γγ (quasi)elastic scattering at the LHC. We find that the cross section for elastic γγ scattering could be measured in the lead-lead collisions for the diphoton invariant mass up to ψ _γγ 15 - 20 GeV. We identify region(s) of phase space where the two-gluon exchange contribution becomes important ingredient compared to box and nonperturbative VDM-Regge mechanisms. We discuss also first results concerning production of two e+e-pairs in UPCs of heavy ions. We considered only double scattering mechanism. [ABSTRACT FROM AUTHOR]