[en] Using an explicitly unitary framework the Okubo-Zweig-Iizuka (OZI) rule is discussed and in particular how this rule is compatible with unitarity. For the phi-ω case unitarity effects (phi→KantiK→ω) contribute a (nearly) imaginary mixing of 0.6 +- 0.1 % and thus cannot account for the whole mixing of 6-10 %. For the f'-f mixing unitarity effects give a much larger value (>6.8%). In order to understand the small experimental f'→2π coupling the process f'→f→2π must be cancelled by another process e.g. f'→fsup((2))→2π, where fsup((2)) is a heavy f-like meson. For the psions above the first important charm threshold unitarity effects are likely to be crucial. At very high energies cancellations can suppress the unitarity effects. But in a transient energy interval (+p particular between the Dsup(*)antiDsup(*) and the Dsup(*)antiDsup(**) thresholds) these cancellations cannot work everywhere because mass differences are important. Therefore (if charm annihilation amplitudes near threshold are not negligibly small), it is expected that in this interval unitarity effects should be the dominant mechanism for the breaking of the OZI rule. Results from a conventional mass matrix mixing analysis are also given in the appendix. (author)

[en] The 35th Physics Days of the Finnish Physical Society will have the traditional structure with plenary lectures, short contributions of young researchers, poster sessions, and social events. The number of members of the society has exceeded 1000 and nearly half of them, more than 400, are expected to participate the Physics Days. The Finnish physicists and the Society can be proud of keeping up this tradition. The annual meeting of the Finnish Physical Society will take place during the Physics Days. I wish all the members of the Finnish Physical Society to attend the meeting and continue the discussions more informally at the conference dinner following the annual meeting. The fifth Magnus Ehrnrooth Price for Physics will be given during the opening ceremony of the Physics Days. Also the winners of the SOLIS competition for high school students will be announced. Traditionally, the Days will end by giving prices for the best poster and the best talk. The 35th Physics Days are held in the new congress center Jyvaeskylae Paviljonki and arranged by the University of Jyvaeskylae. The proceedings includes all the abstracts of the presentations given during the 35th Physics Days

[en] The dynamics of hot matter produced in ultrarelativistic heavy-ion collisions is studied with a cascade simulation. We model the putative quark-gluon plasma with independent globs of high-density matter. The hadronic phase is treated by explicit tracking of pion coordinates. We find that the pions make 0--2 collisions with globs and 1--3 collisions with other pions, under conditions expected for heavy ions at collider energies. The entropy increases by about 20% during the phase transition. The transverse momentum in the final state is almost entirely due to the momentum with which pions are emitted from the globs, except at extremely high densities where the hydrodynamic expansion of the pure plasma phase is significant

[en] The large transverse energies produced in collisions of 200 GeV protons with Pb nuclei in the nuclear fragmentation regime are understood in terms of statistically independent multiple scatterings of the proton, with substantial rescattering and secondary production of excitations in the nucleus. Transverse energy production by scattering of 400 and 80 GeV protons, in the central rapidity regime, does not, on the other hand, appear to require rescattering. The same picture agrees well with preliminary measurements at CERN of transverse energy production in scattering of ¹⁶O on Pb in both the central and target fragmentation regions. (orig.)