1,297 research outputs found
Sequential vector and axial-vector meson exchange and chiral loops in radiative phi decay
We study the radiative decay into and taking into account mechanisms in which there are two sequential
vector-vector-pseudoscalar or axial-vector--vector--pseudoscalar steps followed
by the coupling of a vector meson to the photon, considering the final state
interaction of the two mesons. There are other mechanisms in which two kaons
are produced through the same sequential mechanisms or from decay into
two kaons and then undergo final state interaction leading to the final pair of
pions or , this latter mechanism being the leading one. The results
of the parameter free theory, together with the theoretical uncertainties, are
compared with the latest experimental results of KLOE at Frascati.Comment: 28 pages, 20 figure
Hadron resonances generated from the dynamics of the lightest scalar ones
We have studied the interactions of the scalar resonances f_0(980) and
a_0(980) with the vector resonance \phi(1020) and with the lightest
pseudoscalars \pi, K, \eta and \eta'. We first obtain the interaction kernels
without including any new free parameter. Afterwards, the interaction kernels
are unitarized and the final S-wave amplitudes result. We find that these
interactions are very rich and generate a large amount of pseudoscalar
resonances including the K(1460), \pi(1300), \pi(1800), \eta(1475) and X(1835)
resonances. The f_0(980)\phi(1020) self-interactions give rise to the
\phi(2170) resonance. For realistic choices of the parameters we also obtain an
isovector companion in the same mass region from the a_0(980) \phi(1020)
interactions.Comment: 4 pafes, 4 figures. Invited talk at QCD 10 (25th anniversary), 15th
International QCD Conference, 28th June - 3rd July 2010 Montpellier (France).
To be published in Nucl. Phys. B (Proc. Suppl.
Unitary chiral dynamics in J/Psi to VPP decays and the role of scalar mesons
We make a theoretical study of the J/Psi decays into \omega\pi\pi,
\phi\pi\pi, \omega K \bar{K} and \phi K\bar{K} using the techniques of the
chiral unitary approach stressing the important role of the scalar resonances
dynamically generated through the final state interaction of the two
pseudoscalar mesons. We also discuss the importance of new mechanisms with
intermediate exchange of vector and axial-vector mesons and the role played by
the OZI rule in the J/\Psi\phi\pi\pi vertex, quantifying its effects. The
results nicely reproduce the experimental data for the invariant mass
distributions in all the channels considered.Comment: 29 pages, 10 figure
Non-Perturbative Study of the Light Pseudoscalar Masses in Chiral Dynamics
We perform a non-perturbative chiral study of the masses of the lightest
pseudoscalar mesons. In the calculation of the self-energies we employ the
S-wave meson-meson amplitudes taken from Unitary Chiral Perturbation Theory
(UCHPT) that include the lightest nonet of scalar resonances. Values for the
bare masses of pions and kaons are obtained, as well as an estimate of the mass
of the \eta_8. The former are found to dominate the physical pseudoscalar
masses. We then match to the self-energies from Chiral Perturbation Theory
(CHPT) to O(p^4), and a robust relation between several O(p^4) CHPT
counterterms is obtained. We also resum higher orders from our calculated
self-energies. By taking into account values determined from previous chiral
phenomenological studies of m_s/\hat{m} and 3L_7+L^r_8, we determine a tighter
region of favoured values for the O(p^4) CHPT counterterms 2L^r_6-L^r_4 and
2L^r_8-L^r_5. This determination perfectly overlaps with the recent
determinations to O(p^6) in CHPT. We warn about a likely reduction in the value
of m_s/\hat{m} by higher loop diagrams and that this is not systematically
accounted for by present lattice extrapolations. We also provide a favoured
interval of values for m_s/\hat{m} and 3L_7+L^r_8.Comment: 26 pages, 9 figures. Original new material is included. Major
rewriting when comparing with lattice QC
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
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