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Ariadne, based on the dipole-cascade model, is one of the most successful QCD shower programs when it comes to describing hadronic final states at LEP and HERA. In particular for low- to medium-virtuality processes at HERA it has proven superior to conventional parton showers. Ariadne is now rewritten in C++ using the framework of ThePEG, and includes a new initial-state shower model, called DIPSY, based on dipole evolution in impact-parameter space. This model has recently been adapted to produce exclusive final states with very promising preliminary results both for pp and heavy-ion collisions.

This will be an interesting alternative to the initial-state showers and multiple scattering models of underlying events implemented e.g. in Pythia and Herwig, since it takes into account also the resummation of large logarithms of the small momentum fraction (small-x) of the partons inside the proton, which is important for soft and semi-hard processes at the LHC.

The Ariadne project is closely related to other approaches based on small-x evolution, in particular the HEJ and CASCADE programs. The HEJ program is based on a high-energy multi-jet version of collinear factorization, and is already integrated with the Ariadne program for matching with final-state showers. The CASCADE program is based on the so-called kt-factorization theorem and is developed by members of the DESY group who are associate members of the Lund team.