Christer Friberg

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Pythia version 6 represents a merger of the Pythia 5, Jetset 7 and SPythia programs, with many improvements. It can be used to generate high-energy-physics ‘events’, i.e. sets of outgoing particles produced in the interactions between two incoming particles. The objective is to provide as accurate as possible a representation of event properties in a wide(More)
After a long period of focus on western and Asian scripts there is now a general trend in the on-line handwriting recognition community to explore recognition of other scripts such as Arabic and various Indic scripts. One difficulty with the Arabic script is the number and position of diacritic marks associated to Arabic characters. This paper explores the(More)
The production of jets is studied in collisions of virtual photons, γp and γγ, specifically for applications at HERA and LEP2. Photon flux factors are convoluted with matrix elements involving either direct or resolved photons and, for the latter, with parton distributions of the photon. Special emphasis is put on the range of uncertainty in the modeling of(More)
A high-energy lepton-lepton collider will give us a unique possibility to study eγ and γγ interactions at high energies. The high-energy photons can be generated by Compton back-scattering of laser light on the high-energy lepton beams. With slightly reduced luminosities for eγ and γγ collisions compared to the lepton-lepton collider one, unique and(More)
We have a very limited knowledge about how the confinement mechanism works in processes like ee → qqg . . . g, when there are identical colour charges. In this case the partons can be connected by a string or a cluster chain in several different ways. We do not know if in such a situation Nature chooses a particular configuration at random, or if some(More)
The description of longitudinal photons is far from trivial, and their phenomenological importance is largely unknown. While the cross section for direct interactions is calculable, an even more important contribution could come from resolved states. In the development of our model for the interactions of (real and) virtual photons, we have modeled resolved(More)
A model for total cross sections with virtual photons is presented, in particular γp and γγ cross sections are considered. Our approach is based on an existing model for photoproduction, which subdivides the total cross section into three distinct event classes: direct, VMD and anomalous [1]. In the region of large photon virtualities, the Deep Inelastic(More)