1,731 research outputs found
Dispersive chiral approach to Meson-meson dynamics: Spectroscopy results for light scalars and precision studies
Dispersive approaches provide model independent description of meson-meson
scattering. We first review here the use of dispersion relations to obtain a
model independent unitarization of Chiral Perturbation Theory amplitudes, that
establish the existence of light scalar mesons and whose leading 1/N_c behavior
suggest they ahve a non q-qbar dominant component. We also review the forward
dispersion relation checks on conflicting experimental data and the resulting
very precise pion-pion scattering scattering amplitudes.Comment: 8 pages. Invited Plenary talk at the Conference ``Quark Confinement
and the Hadron SpectrumVII''. 2-7th Sept. 2006. Ponta Delgada, Azores
Islands. Portuga
Large N_c behavior of light resonances in meson-meson scattering
By scaling the parameters of meson-meson unitarized Chiral Perturbation
Theory amplitudes according to the QCD large N_c rules, one can study the
spectroscopic nature of light meson resonances. The scalars sigma, kappa
f_0(980) and, possibly, the a_0(980) do not seem to behave as q-qbar states, in
contrast to the vectors rho(770) and K*(892). The behavior shown by the scalars
is naturally explained in terms of diagrams with intermediate -like states. Here we review our recent study and show how the results do
not depend on the different fits to data.Comment: 6 pages. To appear in the proceedings of the HADRON03 conference,
Aschaffenburg, Germany. September 200
Poles of light resonances from unitarized Chiral perturbation Theory and their large Nc behavior
We have recently completed the one loop calculation of meson-meson scattering
within Chiral Perturbation Theory. Once unitarized, these amplitudes provide
simultaneously a remarkable description of the resonance region up to 1.2 GeV
as well as the low energy region, respecting the chiral symmetry expansion. The
position of the poles in these amplitudes is related to the mass and width of
the associated resonances that are generated without being explicitly included
in the Lagrangian. The spectroscopic nature of these states can then be deduced
by studying the behavior of these poles, through the Nc dependence of the
Chiral Perturbation Theory parameters, which can be obtained from QCD in the
large Nc limit.Comment: Invited talk to the 25th MRST, Conference on High Energy Physics
(``J. Schechter Fest''). May 13 - 15, 2003, Syracuse University, Syracuse,
New York. 13 pages, 2 figure
Consistency checks of different pion-pion scattering data sets using forward dispersion relations
We review our evaluation of forward dispersion relations for direct fits to
the different, and often conflicting, pion-pion scattering experimental
analyses. We find that some of the most commonly used data sets do not satisfy
these constraints by several standard deviations. We also provide a consistent
pion-pion amplitude by improving a global fit to data with these dispersion
relations.Comment: To appear in the Proceedings of the XI. International Conference on
Hadron Spectroscopy- HADRON05. Rio de Janeiro. 21st-25th August. 200
Resonance Spectrum of the strongly interacting Symmetry Breaking Sector
Within the chiral lagrangian formalism it is possible to describe the general
strongly coupled Symmetry Breaking Sector in terms of a few parameters. Based
on a dispersive approach we have studied the resonance spectrum up to 3 TeV in
the chiral parameter space. This procedure could also be useful to extract the
higher energy resonant behavior from low-energy collider data. It is also shown
how the method reproduces the correct pole structure of resonances as well as
other analytic features. The results also hint at a possible excluded region of
parameter space.Comment: 19 LaTeX pages. 6 eps figures. Uses epsf. Postscript available at
http://www-physics.lbl.gov/www/theorypapers/preprints.htm
Light scalar and vector mesons in the large limit from unitarized chiral perturbation theory
We review the large Nc behavior of light scalar and vector resonances
generated from unitarized meson-meson scattering amplitudes at one loop in
Chiral Perturbation Theory. The vectors nicely follow the behavior expected for
qqbar states, whereas scalar mesons do not. This suggests that the main
component of light scalars is not qqbar. We also comment on t-channel vector
exchange as well as on the large Nc behavior of the mass splittings between the
vectors generated from the inverse amplitude method.Comment: Invited talk to the XIth International Conference on Hadron
Spectroscopy, HADRON05, Rio de Janeiro, 22-26 August 200
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