355 research outputs found
f_0(600), kappa(800), rho(770) and K*(892), quark mass dependence from unitarized SU(3) Chiral Perturbation Theory
We study the strange and non-strange quark mass dependence of the parameters
of the f_0(600), kappa(800), rho(770) and K*(892) resonances generated from
elastic meson-meson scattering using unitarized one-loop Chiral Perturbation
Theory. We fit simultaneously all experimental scattering data up to 0.8-1 GeV
together with lattice results on decay constants and scattering lengths up to a
pion mass of 440 MeV. Then, the strange and non-strange quark masses are varied
from the chiral limit up to values of interest for lattice studies. In these
amplitudes, the mass and width of the rho(770) and K*(892) present a similar
and smooth quark mass dependence. In contrast, both scalars present a similar
non-analyticity at high quark masses. Nevertheless the f_0(600) dependence on
both quark masses is stronger than for the kappa(800) and the vectors. We also
confirm the lattice assumption of quark mass independence of the vector
two-meson coupling that, in contrast, is violated for scalars.Comment: To appear in the proceedings of the XIII International Conference on
Hadron Spectroscopy Nov.29-Dec.4, 2009. Tallahassee, Florida, USA. 5 page
Dependence on the quark masses of elastic phase shifts and light resonances within standard and unitarized Chiral Perturbation Theory
We study the dependence of the pion-pion scattering phase shifts on the light
quark mass in both standard and unitarized SU(2) Chiral Perturbation Theory
(ChPT) to one and two loops. We then use unitarized SU(3) ChPT to study the
elastic f_0(600), kappa(800), rho(770) and K*(892) resonances. The quark masses
are varied up to values of interest for lattice studies. We find a very soft
dependence on the light quark mass of the pion-pion phase shifts at one loop
and slightly stronger at two loops and a good agreement with lattice results.
The SU(3) analysis shows that the properties of the rho(770) and K*(892) depend
smoothly on the quark mass whereas the scalar resonances present a
non-analyticity at high quark masses. We also confirm the lattice assumption of
quark mass independence of the vector two-meson coupling that, however, is
violated for scalars.Comment: To appear in the proceedings of the 12th International Conference on
Meson-Nucleon Physics and the Structure of the Nucleon, College of William
and Mary Williamsburg, Virginia, May 31-June 4, 201
Strange and non-strange quark mass dependence of elastic light resonances from SU(3) Unitarized Chiral Perturbation Theory to one loop
We study the light quark mass dependence of the f_0(600), kappa(800),
rho(770) and K*(892) resonance parameters generated from elastic meson-meson
scattering using unitarized one-loop Chiral Perturbation Theory. First, we show
that it is possible to fit simultaneously all experimental scattering data up
to 0.8-1 GeV together with lattice results on decay constants and scattering
lengths up to a pion mass of 400 MeV, using chiral parameters compatible with
existing determinations. Then, the strange and non-strange quark masses are
varied from the chiral limit up to values of interest for lattice studies. In
these amplitudes, the mass and width of the rho(770) and K*(892) present a
similar and smooth quark mass dependence. In contrast, both scalars present a
similar non-analyticity at high quark masses. Nevertheless, the f_0(600)
dependence on the non-strange quark mass is stronger than for the kappa(800)
and the vectors. We also confirm the lattice assumption of quark mass
independence of the vector two-meson coupling that, in contrast, is violated
for scalars. As a consequence, vector widths are very well approximated by the
KSRF relation, and their masses are shown to scale like their corresponding
meson decay constants.Comment: 20 pages, 13 figures. References added to new version and region of
applicability slightly modified. Typos corrected
Identification of non-ordinary mesons from the dispersive connection between their poles and their Regge trajectories: the f0(500) resonance
We show how the Regge trajectory of a resonance can be obtained from its pole
in a scattering process and analytic constraints in the complex angular
momentum plane. The method is suited for resonances that dominate an elastic
scattering amplitude. In particular, from the rho(770) resonance pole in
pion-pion scattering, we obtain its linear Regge trajectory, characteristic of
ordinary quark-antiquark states. In contrast, the f0(500) pole -the sigma
meson- which dominates scalar isoscalar pion-pion scattering, yields a
non-linear trajectory with a much smaller slope at the f0(500) mass.
Conversely, imposing a linear Regge trajectory for the f0(500), with a slope of
typical size, yields an elastic amplitude at odds with the data. This provides
strong support for the non-ordinary nature of the sigma meson.Comment: 8 pages, 4 figure
Regge trajectory of the f_0(500) resonance from a dispersive connection to its pole
We report here our results on how to obtain the Regge trajectory of a
resonance from its pole in a scattering process by imposing analytic
constraints in the complex angular momentum plane. The method, suited for
resonances that dominate an elastic scattering amplitude, has been applied to
the {\rho}(770) and the f_0(500) resonances. Whereas for the former we obtain a
linear Regge trajectory, characteristic of ordinary quark-antiquark states, for
the latter we find a non-linear trajectory with a much smaller slope at the
resonance mass. This provides a strong indication of the non-ordinary nature of
the sigma meson.Comment: 4 pages, 2 figures, to appear in the proceedings of the "Seventh
International Symposium on Chiral Symmetry in Hadrons and Nuclei
Enhanced non-quark-antiquark and non-glueball Nc behavior of light scalar mesons
We show that the latest and very precise dispersive data analyses require a
large and very unnat- ural fine-tuning of the 1/Nc expansion at Nc = 3 if the
f_0(600) and K(800) light scalar mesons are to be considered predominantly
quark-antiquark states, which is not needed for light vector mesons. For this,
we use scattering observables whose 1/Nc corrections are suppressed further
than one power of 1/Nc for quark-antiquark or glueball states, thus enhancing
contributions of other nature. This is achieved without using unitarized ChPT,
but if it is used we can also show that it is not just that the coefficients of
the 1/Nc expansion are unnatural, but that the expansion itself does not even
follow the expected 1/Nc scaling of a glueball or a quark-antiquark meson.Comment: Discussion disfavoring a glueball interpretation added. Version
published in Phys. Rev.
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