1,444 research outputs found
Final State Interactions in Hadronic D decays
We show that the large corrections due to final state interactions (FSI) in
the D^+\to \pi^-\pi^+\pi^+, D^+_s\to \pi^-\pi^+\pi^+, and D^+\to K^-\pi^+\pi^+
decays can be accounted for by invoking scattering amplitudes in agreement with
those derived from phase shifts studies. In this way, broad/overlapping
resonances in S-waves are properly treated and the phase motions of the
transition amplitudes are driven by the corresponding scattering matrix
elements determined in many other experiments. This is an important step
forward in resolving the puzzle of the FSI in these decays. We also discuss why
the \sigma and \kappa resonances, hardly visible in scattering experiments, are
much more prominent and clearly visible in these decays without destroying the
agreement with the experimental \pi\pi and K\pi low energy S-wave phase shifts.Comment: 22 pages, 6 figures, 5 tables. Minor changes. We extend the discusion
when quoting a reference and we include a new one. Some typos are fixe
Recent progress on the chiral unitary approach to meson meson and meson baryon interactions
We report on recent progress on the chiral unitary approach, analogous to the
effective range expansion in Quantum Mechanics, which is shown to have a much
larger convergence radius than ordinary chiral perturbation theory, allowing
one to reproduce data for meson meson interaction up to 1.2 GeV. Applications
to physical processes so far unsuited for a standard chiral perturbative
approach are presented. Results for the extension of these ideas to the meson
baryon sector are discussed, together with applications to kaons in a nuclear
medium and atoms.Comment: Contribution to the KEK Tanashi Symposium on Physics of Hadrons and
Nuclei, Tokyo, December 1998, 10 pages, 3 postscript figures. To be published
as a special issue of Nuclear Physics
Meson Exchange Currents in Kaon Scattering on the Lightest Nuclei
The K^+ scattering on the lightest nuclei, d, 3He and 4He is studied in the
framework of multiple scattering theory. Effects from MEC tied to the
K^+N-->KNpi reaction are evaluated. We found that at momentum transfers Q^2<0.5
(GeV/c)^2 contributions from MEC are much smaller than kaon rescattering
corrections. This makes the conventional multiple scattering picture a reliable
tool to study these reactions in this kinematical domain and to extract the
K^+n scattering amplitude from the K^+d data. At larger transferred momentum
MEC can become more relevant.Comment: revtex, 16 pages, 6 figure
Clues for the existence of two resonances
The axial vector meson was studied within the chiral unitary
approach, where it was shown that it has a two-pole structure. We reanalyze the
high-statistics WA3 experiment at 63 GeV, which
established the existence of both and , and we show that
it clearly favors our two-pole interpretation. We also reanalyze the
traditional K-matrix interpretation of the WA3 data and find that the good fit
of the data obtained there comes from large cancellations of terms of unclear
physical interpretation.Comment: published version in PRD; typos corrected; title changed to "Clues
for the existence of two resonances
Two-photon and one photon-one vector meson decay widths of the , , , , and
We calculate the radiative decay widths, two-photon () and one
photon-one vector meson (), of the dynamically generated resonances
from vector meson-vector meson interaction in a unitary approach based on the
hidden-gauge Lagrangians. In the present paper we consider the following
dynamically generated resonances: , , ,
, , two strangeness=0 and isospin=1 states, and two
strangeness=1 and isospin=1/2 states. For the and we
reproduce the previous results for the two-photon decay widths and further
calculate their one photon-one vector decay widths. For the and
the calculated two-photon decay widths are found to be consistent
with data. The , and decay widths of
the , , , are compared with the
results predicted by other approaches. The and
decay rates of the are also calculated and compared with the
results obtained in the framework of the covariant oscillator quark model. The
results for the two states with strangeness=0, isospin=1 and two states with
strangeness=1, isospin=1/2 are predictions that need to be tested by future
experiments.Comment: More discussions about the relation between qqbar states and
dynamically generated states; version published in PRD
Optimization method for the determination of material parameters in damaged composite structures
An optimization method to identify the material parameters of composite structures using an inverse method is proposed. This methodology compares experimental results with their numerical reproduction using the finite element method in order to obtain an estimation of the error between the results. This error estimation is then used by an evolutionary optimizer to determine, in an iterative process, the value of the material parameters which result in the best numerical fit. The novelty of the method is in the coupling between the simple genetic algorithm and the mixing theory used to numerically reproduce the composite behavior. The methodology proposed has been validated through a simple example which illustrates the exploitability of the method in relation to the modeling of damaged composite structures.Peer ReviewedPostprint (author’s final draft
Recent developments in chiral dynamics of hadrons and hadrons in a nuclear medium
In this talk I present recent developments in chiral dynamics of hadrons and
hadrons in a medium addressing the following points: interaction of the octet
of pseudoscalar mesons with the octet of baryons of the nucleon, showing recent
experimental evidence on the existence of two states, the
interaction of the octet of pseudoscalar mesons with the decuplet of baryons of
the , with particular emphasis on the resonance,
dynamically generated by this interaction. Then I review the interaction of
kaons in a nuclear medium and briefly discuss the situation around the claims
of deeply bound states in nuclei. The large renormalization of the
in the nuclear medium is shown as another example of successful
application of the chiral unitary techniques.Comment: Talk at the Fifth International Conference on Perspectives in
Hadronic Physics: Particle-Nucleus and Nucleus-Nucleus Scattering at
Relativistic Energies, Trieste, May 200
decay within unitarized chiral perturbation theory
We improve the calculations of the decay
within the context of meson chiral lagrangians. We use a chiral unitary
approach for the meson-meson interaction, thus generating the
resonance and fixing the longstanding sign ambiguity on its contribution. This
also allows us to calculate the loops with one vector meson exchange, thus
removing a former source of uncertainty. In addition we ensure the consistency
of the approach with other processes. First, by using vector meson dominance
couplings normalized to agree with radiative vector meson decays. And, second,
by checking the consistency of the calculations with the related reaction. We find an decay width
of eV, in clear disagreement with published data but in
remarkable agreement with the most recent measurement.Comment: 15 pages, 10 figures, published versio
Light scalars as tetraquarks or two-meson states from large Nc and unitarized Chiral Perturbation Theory
By means of unitarized Chiral Perturbation Theory it is possible to obtain a
remarkable description of meson-meson scattering amplitudes up to 1.2 GeV, and
generate poles associated to scalar and vector resonances. Since Chiral
Perturbation Theory is the QCD low energy effective theory, it is possible then
to study its large Nc limit where qqbar states are easily identified. The
vectors thus generated follow closely a qqbar behavior, whereas the light
scalar poles follow the large Nc behavior expected for a dominant tetraquark or
two-meson structure.Comment: Invited Brief Report to appear in Modern Physcis Letters A. 15 page
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