4,357,220 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
Orographic Disturbances of Upper Atmosphere Emissions
There are some increases of the temperature of the hydroxyl emission (delta T approximately 20 K, z approximately 90 km) and of the intensity of the 63000 oxygen emission (delta I/I approximately 20 per cent, z approximately 250 km) for the lee of the mountains at distances about 150 km in the case of the latitudinal direction of the wind (U approximately 10 m/s) at the 3000 m level. Airflow motions over mountains may be one of the possible processes of generation of wave disturbances penetrating into the upper atmospheres (HINES, 1974; LINDZEN, 1971). The purpose here is to study the penetration of orographic disturbances into upper atmosphere. Airplane measurements of emission variations of hydroxyl and atomic oxygen 6300 A near the Northern Ural mountains were made. Several nocturnal flights were carried out in March, 1980 and January to February, 1981 at heights about 3000 m along 64 deg northern latitude in the Ural region. Spectrographs SP-48 with electronic image converters registration for OH ((9,4) and (5,1) bands - 7700 to 8100 A) and OI (6300 A) emissions were used. The zenith region was observed, and exposure time was 2 minutes. This corresponds to averaging of the emission intensities along the airplane trace over a distance of 10 km. Simultaneous measurements of atmospheric temperature variations at the flight altitude were made
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
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
Spin-Spin Interactions in Gauge Theory of Gravity, Violation of Weak Equivalence Principle and New Classical Test of General Relativity
For a long time, it is generally believed that spin-spin interactions can
only exist in a theory where Lorentz symmetry is gauged, and a theory with
spin-spin interactions is not perturbatively renormalizable. But this is not
true. By studying the motion of a spinning particle in gravitational field, it
is found that there exist spin-spin interactions in gauge theory of gravity.
Its mechanism is that a spinning particle will generate gravitomagnetic field
in space-time, and this gravitomagnetic field will interact with the spin of
another particle, which will cause spin-spin interactions. So, spin-spin
interactions are transmitted by gravitational field. The form of spin-spin
interactions in post Newtonian approximations is deduced. This result can also
be deduced from the Papapetrou equation. This kind of interactions will not
affect the renormalizability of the theory. The spin-spin interactions will
violate the weak equivalence principle, and the violation effects are
detectable. An experiment is proposed to detect the effects of the violation of
the weak equivalence principle.Comment: 17 pages, no figur
The Running BFKL: Resolution of Caldwell's Puzzle
The HERA data on the proton structure function, , at very small
and show the dramatic departure of the logarithmic slope, , from theoretical predictions based on the DGLAP
evolution. We show that the running BFKL approach provides the quantitative
explanation for the observed and/or -dependence of .Comment: 7 pages, Latex, 4 Figures, P
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
Gapless Hartree-Fock-Bogoliubov Approximation for Bose Gases
A dilute Bose system with Bose-Einstein condensate is considered. It is shown
that the Hartree-Fock-Bogolubov approximation can be made both conserving as
well as gapless. This is achieved by taking into account all physical
normalization conditions, that is, the normalization condition for the
condensed particles and that for the total number of particles. Two Lagrange
multipliers, introduced for preserving these normalization conditions, make the
consideration completely self-consistent.Comment: Latex file, 22 pages, 2 figure
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