We discuss production of two pairs of cc within a simple formalism of double-parton scattering (DPS). Surprisingly very large cross sections, comparable to single-parton scattering (SPS) contribution, are predicted for LHC energies. Both total inclusive cross section as a function of energy and differential distributions for √ s are shown. We discuss a perspective how to identify the double scattering contribution.

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We investigate different methods to incorporate the effect of photons in hard processes. We compare two different approaches used for calculating cross sections for two-photon pp → l + l − X process. In one of the approaches photon is treated as a collinear parton in the proton. In the second approach recently proposed a k T -factorization method is used. We discuss how results of the collinear parton model depend on the initial condition for the QCD evolution and discuss an approximate treatment where photon is excluded from the combined QCD-QED evolution. We demonstrate that it is not necessary to put photon into the evolution equation as often done recently but it is sufficient to use a simplified approach in which photon couples to quarks and antiquarks which by themselves undergo DGLAP evolution equations. We discuss sensitivity of the results to the choice of structure function parametrization and experimental cuts in the k T -factorization approach. A new optimal structure function parametrization is proposed. We compare results of our calculations with recent experimental data for dilepton production and find that in most cases the contribution of the photon-photon mechanism is rather small. We discuss how to enhance the photon-photon contribution. We also compare our results to those of recent measurements of exclusive and semi-exclusive e + e − pair production with certain experimental data by the CMS collaboration.

W + W − production is one of the golden channels for testing the Standard Model as well for searches beyond the Standard Model. We discuss many new subleading processes for inclusive production of W + W − pairs generally not included in the literature so far. We focus on photon-photon induced processes. We include elastic-elastic, elastic-inelastic, inelastic-elastic and inelastic-inelastic contributions. We also calculate the contributions with resolved photons including the partonic substructure of the virtual photon. Predictions for the total cross section and differential distributions in W -boson rapidity and transverse momentum as well as W W invariant mass are presented. The γγ components constitute only about 1-2 % of the inclusive W + W − cross section but increases up to about 10 % at large W ± transverse momenta, and are even comparable to the dominant qq component at large M W W , i.e. are much larger than the gg → W + W − one.

At high-energies the gluon-gluon fusion is the dominant mechanism of cc production. This process was calculated in the NLO collinear as well as in the k t -factorization approaches in the past. We show that the present knowledge of gluon distributions does not allow to make a precise predictions for cc production at LHC, in particular at forward rapidities. In this paper we study production of cc pairs including several subleading mechanisms. This includes: gg → QQ, γg → QQ, gγ → QQ, γγ → QQ. In this context we use MRST-QED parton distributions which include photon as a parton in the proton as well as elastic photon distributions calculated in the equivalent photon approximation. We present distributions in the c quark (c antiquark) rapidity and transverse momenta and compare them to the dominant gluon-gluon fusion contribution. We discuss also inclusive single and central diffractive processes using diffractive parton distribution found from the analysis of HERA diffractive data. As in the previous case we present distribution in c (c) rapidity and transverse momentum. Finally we present results for exclusive central diffractive mechanism discussed recently in the literature. We show corresponding differential distributions and compare them with corresponding distributions for single and central diffractive components.