2,210 research outputs found
Nature of the a_0(980) Meson in the Light of Photon-Photon Collisions
New high-statistics Belle data on the reaction \gamma\gamma\to\pi^0\eta are
analyzed to clarify the two-photon production mechanisms and the nature of the
a_0(980) meson. The obtained solution for the amplitude
\gamma\gamma\to\pi^0\eta is consistent with the chiral theory expectation for
the \pi\eta scattering length, with the strong coupling of the a_0(980) to the
\pi\eta, K\bar K, and \pi\eta' channels, and with a key role of the
rescattering mechanisms a_0(980)\to(K\bar K+
\pi^0\eta+\pi^0\eta')\to\gamma\gamma in the a_0(980)\to\gamma\gamma decay. Such
a picture argues in favor of the q^2\bar q^2 nature of the a_0(980) meson and
is in agreement with the properties of its partners, the \sigma_0(600) and
f_0(980) mesons, in particular, with those that manifest themselves in
\gamma\gamma\to\pi\pi. An important role of the vector meson exchanges in the
formation of the nonresonant background in \gamma\gamma\to\pi^0\eta is also
revealed. The preliminary information on the reaction \pi^0\eta\to\pi^0\eta is
obtained.Comment: 7 pages, 5 figures, minor corrections and some comments adde
Lightest scalar and tensor resonances in after the Belle experiment
New high statistics Belle data on the reaction
cross section measured in the range of pion-pair invariant masses
between 0.8 GeV and 1.5 GeV are analyzed to clarify the current situation
around the , , and resonances in
collisions. The present analysis shows that the direct coupling
constants of the and resonances to are
small, and the and
decays are four-quark transitions caused by the and loop
mechanisms, respectively. The chiral shielding of the resonance
takes place in the reactions as well as in
scattering. Some results of a simultaneous description of the
and Belle data are also
presented. In particular, the following tentative estimate of the
decay width is obtained:
keV.Comment: 14 pages, 5 figures. Fitted for the publication in Physical Review
The analytical scattering amplitude and the light scalars
In this work we construct the scattering amplitude with
regular analytical properties in the complex plane, which describes
simultaneously the data on the scattering,
decay, and reaction. The chiral shielding of the meson and its mixing with the meson are also taken into
account. The data agrees with the four-quark nature of the and
mesons. The amplitude in the range GeV
also agrees with results, obtained on the base of the chiral expansion,
dispersion relations, and the Roy equations.Comment: Published version: a few clarifications are added, the Editors
corrections are taken into accoun
Proposed Search for Mixing in Polarization Phenomena
The and meson mass difference induces the mixing of the
and resonances, the amplitude of which, between the
and thresholds, is large in magnitude, of the order of , and possesses the
phase sharply varying by about 90. We suggest performing the polarized
target experiments on the reaction at high energy in
which the fact of the existence of mixing can be
unambiguously and very easily established through the presence of a strong jump
in the azimuthal asymmetry of the wave production cross section
near the thresholds. The presented estimates of the polarization
effect to be expected in experiment are to a great extent model independent.Comment: RevTeX, 9 pages, 1 figure. A number of typographical and grammatical
errors correcte
Light Scalar Mesons as Manifestation of Spontaneously Broken Chiral Symmetry
Attention is paid to the production mechanisms of light scalars that reveal
their nature. We reveal the chiral shielding of the \sigma(600) meson. We show
that the kaon loop mechanism of the \phi radiative decays, ratified by
experiment, points to the four-quark nature of light scalars. We show also that
the light scalars are produced in the two photon collisions via four-quark
transitions in contrast to the classic P wave tensor q\bar q mesons that are
produced via two-quark transitions . The history of
spontaneous breaking of symmetry in quantum physics is discussed in Appendix.Comment: Talk at The International Bogolyubov Conference "Problems of
Theoretical and Mathematical Physics" devoted to the 100th anniversary of
N.N.Bogolyubov's birth that was held from August 21 to August 22,2009 in
Moscow at the Russian Academy of Sciences (RAS) and from August 23 to August
27, 2009 in Dubna at the Joint Institute for Nuclear Research (JINR
Light scalars in semi-leptonic decays of heavy quarkonia
We study the mechanism of production of the light scalar mesons in the
decays: , and compare it with the
mechanism of production of the light pseudoscalar mesons in the decays: .
We show that the transition is negligibly small in
comparison with the one. As for the the meson,
the intensity of the transition makes near thirty percent
from the intensity of the () transition. So,
the decay supports the previous conclusions about a
dominant role of the four-quark components in the and
mesons.Comment: 8 pages, 3 figures, the variant matches the publication in Phys. Rev.
Analysis of preliminary data on reaction
We perform the analysis of the preliminary data on reaction simultaneously with the data on
scattering and reactions and
. It is found that the meson mass
MeV and .Comment: 8 pages, revtex, 3 ps files of figures, minor change
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