183 research outputs found
The 1/N_c Approach for Baryon Resonances
I give a brief overview of the model-independent analysis of unstable baryon
resonances in the 1/N_c QCD expansion. This approach produces numerous
surprising semi-quantitative phenomenological predictions that are supported by
available observations.Comment: 4 pages, LaTeX, style file included. Invited talk at International
Conference on QCD and Hadronic Physics, Beijing, China, 16-20 Jun 200
Baryons, IN_c
Excited baryons may be analyzed in the 1/N_c expansion as true resonances in
scattering amplitudes. The key idea making this program possible is a
generalization of methods originally applied to chiral soliton models in the
1980's. One finds model-independent relations among amplitudes that impose mass
and width degeneracies among resonances of various quantum numbers.
Phenomenological evidence demonstrates that patterns of resonant decay
predicted by 1/N_c agree with data. The analysis can be extended to subleading
orders in 1/N_c, where again agreement with data is evident.Comment: 10 pages. Invited talk at "Continuous Advances in QCD 2004,"
Minneapolis, 13-16 Ma
QCD Constraints on Form Factor Shapes
This talk presents an introduction to the use of dispersion relations to
constrain the shapes of hadronic form factors consistent with QCD. The
applications described include methods for studying |V_{cb}| and |V_{ub}|, the
strange quark mass, and the pion charge radius.Comment: 8 pages, 3 eps figures, presented at ``Exclusive & Semi-exclusive
Processes at High Momentum Transfer,'' Jefferson Lab, Newport News, VA, May
20-22, 199
The Pentaquark Candidates in the Dynamical Diquark Picture
Starting with the dynamical picture of the exotic -containing states
as the confinement-induced hadronization of a rapidly separating pair
of a compact diquark and antidiquark, we describe the pentaquark candidates
and in terms of a confined but rapidly separating
color-antitriplet diquark and color-triplet "triquark" . This
separation explains the relatively small widths, despite these 5-quark
systems lying far above both the and
thresholds. The states are predicted to form isospin doublets with
neutral partners .Comment: 5 pages, 1 pdf figure, pdflatex. Version accepted by Phys. Lett.
N* Properties from the 1/N_c Expansion
The 1/N_c expansion (N_c being the number of QCD colors) has been applied in
recent papers to the phenomenology of excited baryon resonances. This talk
surveys the work done to date, and discusses its successes and remaining
challenges.Comment: 10 pages, 1 figure. Invited plenary talk at NSTAR 2002, Pittsburgh,
PA, 9-12 October 200
Explicit Quark-Hadron Duality in 1+1 Dimensions
Explicit quark-hadron duality in the limit of heavy quark mass is studied
using the 't Hooft model, where both partonic and hadronic amplitudes may be
computed exactly. Results for weak decays of heavy mesons are presented for
both standard spectator decays, where the duality limit is convincingly
approached, and annihilation decays of the valence quark-antiquark pair, where
the approach to asymptotic duality is much less precise.Comment: 4 pages, Latex (worldsci.sty), 3 eps figures. Talk presented at the
Third International Conference on Quark Confinement and the Hadron Spectrum,
Jefferson Lab, Newport News, Virginia, June 7-12, 1998; to appear in
Proceeding
NN Interactions in QCD: Old and New Techniques
Since QCD is believed to be the underlying theory of the strong interaction,
it is appropriate to study techniques that take into account more features of
its rich and complex structure. We begin by discussing aspects of physics that
are ill-reproduced by the usual one- or two-meson exchange approaches and
identify the source of the deficiencies of these models. We then reveal
promising methods for curing some of these ills, such as new quark potential
models, baryon chiral perturbation theory, soluble strongly-interacting field
theories, and large N_c QCD.Comment: 14 pages, 3 eps figures, latex, uses sprocl.sty and psfig. Invited
talk presented at ``Mesons and Light Nuclei,'' Aug. 31 - Sept. 4, 1998,
Pruhonice (Prague), Czech Republic; to appear in Proceeding
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