3,657 research outputs found
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
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
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
Hybrid meson properties in Lattice QCD and Flux Tube Models
Flux tube model predictions for hybrid meson decays are beginning to be
confronted by Lattice QCD. We compare the two approaches for the -wave decay
of the exotic , and find excellent agreement. Results suggest that in
Strong QCD, \qq~ creation occurs with S=1.Comment: 6 pages, 1 figure, v2: discussion of parameters and lattice
uncertainties adde
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
Scalar Glueball-qqbar Mixing above 1 GeV and implications for Lattice QCD
Lattice QCD predictions have motivated several recent studies of the mixing
between the predicted JPC = 0++ glueball and a qqbar nonet in the 1.3 to 1.7
GeV region. We show that results from apparently different approaches have some
common features, explain why this is so and abstract general conclusions. We
place particular emphasis on the flavour dependent constraints imposed by
decays of the f0(1370), f0(1500) and f0(1700) to all pairs of pseudoscalar
mesons. From these results we identify a systematic correlation between
glueball mass, mixing, and flavour symmetry breaking and conclude that the
glueball may be rather lighter than some quenched lattice QCD computations have
suggested. We identify experimental tests that can determine the dynamics of a
glueball in this mass region and discuss quantitatively the feasibility of
decoding glueball-qqbar mixing.Comment: 33 pages, Latex, 4 Figure
Symmetry breaking and quark-hadron duality in structure functions
We identify conditions under which a summation over nucleon resonances can
yield, via quark-hadron duality, parton model results for electromagnetic and
neutrino structure functions at large x. While a summation over the lowest even
and odd parity multiplets is sufficient to achieve duality in the symmetric
quark model, a suppression of transitions to specific final states is required
for more realistic cases incorporating SU(6) breaking. We outline several
scenarios consistent with duality, discuss their implications for the high Q^2
behavior of transition form factors, and illustrate how they can expose the
patterns in the flavor-spin dependence of inter-quark forces.Comment: 30 pages, 9 figures, to appear in Phys. Rev.
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