R. Žlebčík

Factorisation breaking in diffractive dijet photoproduction at HERA

Recent experimental data on dijet cross sections in diffractive photoproduction at HERA collider are analysed with an emphasis on QCD factorisation breaking effects. The possible sources of the different conclusions of H1 and ZEUS collaborations are studied.

Generation of central exclusive final states

We present a scheme for the generation of central exclusive final states in the program. The implementation allows for the investigation of higher-order corrections to such exclusive processes as approximated by the initial-state parton shower in . To achieve this, the spin and colour decomposition of the initial-state shower has been worked out, in order to determine the probability that a partonic state generated from an inclusive sub-process followed by a series of initial-state parton splittings can be considered as an approximation of an exclusive colour- and spin-singlet process. We use our implementation to investigate the effects of parton showers on some examples of central exclusive processes, and we find sizeable effects on di-jet production, while the effects on e.g. central exclusive Higgs production are minor.