4,357,220 research outputs found

    Nature of the a_0(980) Meson in the Light of Photon-Photon Collisions

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    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 γγππ\gamma\gamma\to\pi\pi after the Belle experiment

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    New high statistics Belle data on the γγπ+π\gamma\gamma\to\pi^+\pi^- reaction cross section measured in the range of pion-pair invariant masses s\sqrt{s} between 0.8 GeV and 1.5 GeV are analyzed to clarify the current situation around the σ(600)\sigma(600), f0(980)f_0(980), and f2(1270)f_2(1270) resonances in γγ\gamma\gamma collisions. The present analysis shows that the direct coupling constants of the σ(600)\sigma(600) and f0(980)f_0(980) resonances to γγ\gamma\gamma are small, and the σ(600)γγ\sigma(600)\to\gamma\gamma and f0(980)γγf_0(980)\to\gamma\gamma decays are four-quark transitions caused by the π+π\pi^+\pi^- and K+KK^+K^- loop mechanisms, respectively. The chiral shielding of the σ(600)\sigma(600) resonance takes place in the reactions γγππ\gamma\gamma\to\pi\pi as well as in ππ\pi\pi scattering. Some results of a simultaneous description of the γγπ+π\gamma\gamma\to\pi^+\pi^- and γγπ0π0\gamma\gamma\to\pi^0\pi^0 Belle data are also presented. In particular, the following tentative estimate of the f2(1270)γγf_2(1270)\to\gamma\gamma decay width is obtained: Γf2γγ(mf22)3.68\Gamma_{f_2\to\gamma\gamma}(m^2_{f_2})\approx 3.68 keV.Comment: 14 pages, 5 figures. Fitted for the publication in Physical Review

    Orographic Disturbances of Upper Atmosphere Emissions

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    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 a00(980)f0(980)a^0_0(980)-f_0(980) Mixing in Polarization Phenomena

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    The K+K^+ and K0K^0 meson mass difference induces the mixing of the a00(980)a^0_0(980) and f0(980)f_0(980) resonances, the amplitude of which, between the K+KK^+K^- and K0Kˉ0K^0\bar K^0 thresholds, is large in magnitude, of the order of mKmK02mK+2αmK2 m_{K}\sqrt{m^2_{K^0}-m^2_{K^+}}\approx\sqrt\alpha m^2_K, and possesses the phase sharply varying by about 90^\circ. We suggest performing the polarized target experiments on the reaction πpηπ0n\pi^-p\to\eta\pi^0n at high energy in which the fact of the existence of a00(980)f0(980)a^0_0(980)-f_0(980) mixing can be unambiguously and very easily established through the presence of a strong jump in the azimuthal asymmetry of the ηπ0\eta\pi^0 SS wave production cross section near the KKˉK\bar K 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 ππ\pi\pi scattering amplitude and the light scalars

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    In this work we construct the ππ\pi\pi scattering amplitude T00T^0_0 with regular analytical properties in the ss complex plane, which describes simultaneously the data on the ππ\pi\pi scattering, ϕπ0π0γ\phi\to\pi^0\pi^0\gamma decay, and ππKKˉ\pi\pi\to K\bar K reaction. The chiral shielding of the σ(600)\sigma (600) meson and its mixing with the f0(980)f_0(980) meson are also taken into account. The data agrees with the four-quark nature of the σ(600)\sigma (600) and f0(980)f_0(980) mesons. The amplitude in the range 5mπ2<s<0.64-5 m_\pi^2 < s < 0.64 GeV2^2 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

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    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

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    The HERA data on the proton structure function, F2(x,Q2)F_2(x,Q^2), at very small xx and Q2Q^2 show the dramatic departure of the logarithmic slope, F2/logQ2\partial F_2/\partial\log Q^2, from theoretical predictions based on the DGLAP evolution. We show that the running BFKL approach provides the quantitative explanation for the observed xx and/or Q2Q^2 -dependence of F2/logQ2\partial F_2/\partial\log Q^2.Comment: 7 pages, Latex, 4 Figures, P

    Light Scalar Mesons as Manifestation of Spontaneously Broken Chiral Symmetry

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    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 γγqqˉ\gamma\gamma\to q\bar q. 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

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    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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