Multiparticle Dynamics 2004

We summarize results presented at this conference with special emphasis on hard processes with jets and heavy quarks, soft particle production, small x structure functions and diffraction as well as heavy ion collisions and quark gluon plasma.Comment: Summary talk at XXXIV International Symposium on Multiparticle Dynamics (ISMD 2004), Sonoma State University, Rohnert Park, California, July 26 - August 1, 2004, 21 pages, 4 figure

Soft Limits of Multiparticle Observables and Parton Hadron Duality

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

No indication of f0(1370) in pi pi phase shift analyses

The scalar meson f_0(1370) - indicated in particular in the low energy p\bar p \to 3 body reactions - is a crucial element in certain schemes of the scalar meson spectroscopy including glueballs. The most definitive results can be obtained from elastic and inelastic pi pi phase shift analyses using the constraints from unitarity where the discrete ambiguities can be identified and resolved. We reconsider the phase shift analyses for pi^+ pi^- \to pi+ \pi-, pi^0 pi^0, K \bar K, eta eta. While a clear resonance signal for f_0(1500) in the resp. Argand diagrams is seen in all channels above a large ``background'' from f_0(600) there is no clear signal of a second resonance ``f_0(1370)'' in this mass range in any reaction, at the level of \sim 10% branching ratio into pi-pi.Comment: 5 pages, 3 figures. Conference on Hadron Spectroscopy (Hadron2009), Tallahassee, Florida, Nov 29 - Dec 4, 200

The Status of Glueballs

Calculations within QCD (lattice and sum rules) find the lightest glueball to be a scalar and with mass in the range of about 1000-1700 MeV. Several phenomenological investigations are discussed which aim at the identification of the scalar meson nonets of lowest mass and the super-numerous states if any. Results on the flavour structure of the light scalars f0(500), f0(980) and f0(1500) are presented; the evidence for f0(1370) is scrutinized. A significant surplus of leading clusters of neutral charge in gluon jets is found at LEP in comparison with MCs, possibly a direct signal for glueball production; further studies with more energetic jets at LHC are suggested. As a powerful tool in the identification of the scalar nonets or other multiplets, along with signals from glueballs we propose the exploration of symmetry relations for decay rates of C=+1 heavy quark states like chi-c or chi-b. Results from chi-c decays are discussed; they are not in support of a tetra-quark substructure of f0(980). A minimal scenario for scalar quarkonium - glueball spectroscopy is presented.Comment: Topical Review for J.Phys.G: Nuclear and Particle Physics, 80 pages, 25 figures, 15 tables, typos correcte