Production of $t\overline{t}$ pairs via γγ fusion with photon transverse momenta and proton dissociation

We discuss the production of $t\overline{t}$ quark-antiquark pairs in proton-proton collisions via the γγ fusion mechanism. We include topologies in which both protons stay intact or one or even both of them undergo dissociation. The calculations are performed within the k_T-factorisation approach, including transverse momenta of intermediate photons. Photon fluxes associated with inelastic (dissociative) processes are calculated based on modern parameterisations of proton structure functions. We find an integrated cross section of about 2.36 fb at $\sqrt{s}=13$ TeV for all contributions (without requirement of rapidity gap). The cross section for the fully elastic process is the smallest. Inelastic contributions are significantly reduced when a veto on outgoing jets is imposed. We present several differential distributions in rapidity and transverse momenta of single t or $\overline{t}$ quarks/antiquarks as well as distributions in invariant mass of both the $t\overline{t}$ and masses of dissociated systems. A few two-dimensional distributions are presented in addition.