6,715 research outputs found

    Soft Limits of Multiparticle Observables and Parton Hadron Duality

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    We discuss observables in multiparticle production for three kinds of limits of decreasing kinematical scales: 1. the transition jet \to hadron (limit y_{cut}\to 0 of the resolution parameter y_{cut}); 2. single particle inclusive distributions normalized at threshold \sqrt s\to 0 and 3. particle densities in the limit of low momentum p,p_T\to 0. The observables show a smooth behaviour in these limits and follow the perturbative QCD predictions, originally designed for large scales, whereby a simple prescription is supplemented to take into account mass effects. A corresponding physical picture is described.Comment: talk at Ringberg workshop "New trends in HERA physics 1999", Tegernsee, May 1999; LaTeX, 13 pages, 6 Fig

    Light scalar meson spectrum

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    We discuss the classification of the light scalar mesons with mass below 2 GeV into q qbar nonets and glueballs. The information on production and decay of these states, in particular recent information on f_0(980), f_0(400-1200) (or sigma(600)) and f_0(1500) is considered. Although the data are not yet very precise the recent information is in favour of the previously developed scheme which includes f_0(980), a_0(980), K_0^*(1430), f_0(1500) into the lightest scalar nonet. The glueball in this approach appears as broad object around 1 GeV. Alternative schemes find the glueball at somewhat higher mass or suggest his mixing with q qbar states spread over a similar mass range. We do not see sufficient evidence yet for a light scalar nonet below 1 GeV around a sigma(600) resonance.Comment: Plenary talk at IXth International Conference on Hadron Spectroscopy (HADRON 2001), Protvino, Russia, August 2001; to be publ. in AIP Conf. Proceedings, 11 pages, Latex, AIP macro