209 research outputs found
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
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
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
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