148 research outputs found
Evidence that the Pomeron transforms as a non-conserved vector current
The detailed dependences of central meson production on the azimuthal angle
phi, t and the meson J^P are shown to be consistent with the hypothesis that
the soft Pomeron transforms as a non-conserved vector current. Further tests
are proposed. This opens the way for a quantitative description of q-qbar and
glueball production in p p -> p M p.Comment: 12 pages, latex, 4 figure
Quarks, diquarks and QCD mixing in the resonance spectrum
We identify a " selection rule" for resonances in the presence
of QCD mixing effects. We quantify these mixing effects from existing data and
predict amplitudes for exciting {\bf 20} representations in SU(6), which are
forbidden in strict diquark models. By classifying Particle-Data-Group (PDG)
states at N=2, we show that , , ,
, and are ideal probes of baryon dynamics
and for establishing whether strongly correlated diquarks survive for .Comment: Extended version accepted by PR
Restricted locality of quark-hadron duality in exclusive meson photoproduction reactions above the resonance region
We show how deviations from the dimensional scaling laws for exclusive
processes may be related to a breakdown in the locality of quark-hadron
duality, i.e. the "restricted locality". For exclusive reactions like meson
photo- and electroproduction above the resonance region, we explore the effects
arising from such a local duality breaking and propose that it can be a
possible source for oscillations about the smooth quark counting rule predicted
by pQCD in the 90-degree differential cross sections.Comment: Contribution to the 10th International Symposium on Meson-Nucleon
Physics and the Structure of the Nucleon (MENU2004), Beijing, 2004; presented
by Q
Scalar mesons above and below 1 GeV
We show that two nonets and a glueball provide a consistent description of
data on scalar mesons below 1.7 GeV. Above 1 GeV the states form a conventional
(q bar q) nonet mixed with the glueball of lattice QCD. Below 1 GeV the states
also form a nonet, as implied by the attractive forces of QCD, but of more
complicated nature. Near the center they are 4 quark states of the Jaffe type
in S-wave, with some (q bar q) in P-wave, but further out they rearrange in
colour to two colourless (q bar q) pairs and finally as meson-meson states. A
simple effective chiral model for such a system with two scalar nonets can be
made involving two coupled linear sigma models. One of these could be looked
upon as the Higgs sector of nonpertubative QCD.Comment: 34 pages in Latex, minor improvements in sec
The origins of quark-hadron duality: How does the square of the sum become the sum of the squares?
Bloom-Gilman duality demonstrates empirically that the electroproduction of
's at low momentum transfers averages smoothly around the scaling curve
measured at large momentum transfers. The latter is proportional to the sum of
the squares of the constituent charges whereas the former involves the coherent
excitation of resonances and is driven by the square of summed constituent
charges. We determine the minimal necessary conditions for this equality to be
realised so that duality can occur and consider the implications for a range of
processes that may be studied soon at CEBAF.Comment: 9 page
On baryon-antibaryon coupling to two photons
We discuss recent claims that may be described
by a generalized parton picture. We propose that quark-hadron duality provides
a justification for the effective dominance of the "handbag" diagram assumed in
recent literature, and that handbag diagrams may dominate phenomena in
kinematic regions far more extensive than that might be expected from pQCD
alone.Comment: 11 pages, 2 eps figures, minor modifications made, version to appear
on Phys. Lett.
Light Hadron Spectroscopy: Theory and Experiment
Rapporteur talk at the Lepton-Photon Conference, Rome, July 2001: reviewing
the evidence and strategies for understanding scalar mesons, glueballs and
hybrids, the gluonic Pomeron and the interplay of heavy flavours and light
hadron dynamics. Dedicated to the memory of Nathan Isgur, long-time
collaborator and friend, whose original ideas in hadron spectroscopy formed the
basis for much of the talk.Comment: to be published in "Lepton Photon 2001 Conference Proceedings" (World
Scientific Publishing), 19 pages with 6 figure
Production of , , and in hadronic decays
A coherent study of the production of (, 2, 3 corresponding to
, , and ) in is
reported based on a previously proposed glueball and nonet mixing
scheme, and a factorization for the decay of , where
denotes the isoscalar vector mesons and , and denotes
pseudoscalar mesons. The results show that the decays are very
sensitive to the structure of those scalar mesons, and suggest a glueball in
the GeV region, in line with Lattice QCD. The presence of significant
glueball mixings in the scalar wavefunctions produces peculiar patterns in the
branching ratios for , which are in good agreement
with the recently published experimental data from the BES collaboration.Comment: Version accepted by PRD; Numerical results in Tab IV and VI changed
due to correction of an error in quoting an experimental datum; Conclusion is
not change
The Pentaquark in and , and its partner
A systematic lowering in mass of strangeness ambiguous peaks
relative to the is noted. We discuss how measurement of in association with
can help to clarify the nature of
the narrow baryon state claimed in invariant mass distributions. This
can both establish the in a single experiment and also reveal, or
place severe limits on, the existence of an associated pentaquark
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