Central $\mu^{+}\mu^{-}$ production via photon-photon fusion in   proton-proton collisions with proton dissociation
  We present a formalism which uses fluxes of equivalent photons including transverse momenta of the intermediate photons. The formalism reminds the familiar $k_t$-factorization approach used, e.g., to study the two-photon production of $c\bar{c}$ or $b\bar{b}$ pairs. The results of the new method are compared with those obtained using the code LPAIR, and a good agreement is obtained. The inclusion of the photon transverse momenta is necessary in studies of correlation observables. We present distributions for the dimuon invariant mass, transverse momentum of the muon pair and relative azimuthal angle between muons separately for elastic-elastic, elastic-inelastic, inelastic-elastic and inelastic-inelastic mechanisms. For typical experimental cuts all mechanisms give similar contributions. The results are shown for different sets of cuts relevant for the LHC experiments. The cross sections in different regions of phase space depend on $F_2$ structure function in different regions of $x$ and $Q^2$. A comment on $F_2$ is made. 
Gustavo Gil da Silveira, Laurent Forthomme, Krzysztof Piotrzkowski,   Wolfgang Sch\"afer, and Antoni Szczurek
hep-ph hep-ex