Charge form factor of π\pi and KK mesons

The charge form factor of $\pi$ and $K$ mesons is evaluated adopting a relativistic constituent quark model based on the light-front formalism. The relevance of the high-momentum components of the meson wave function, for values of the momentum transfer accessible to $CEBAF$ energies, is illustrated. The predictions for the elastic form factor of $\pi$ and $K$ mesons are compared with the results of different relativistic approaches, showing that the measurements of the pion and kaon form factors planned at $CEBAF$ could provide information for discriminating among various models of the meson structure.Comment: 8 pages, latex, 4 figures available as separate .uu fil

Ward Identities, B-> \rho Form Factors and |V_ub|

The exclusive FCNC beauty semileptonic decay B-> \rho is studied using Ward identities in a general vector meson dominance framework, predicting vector meson couplings involved. The long distance contributions are discussed which results to obtain form factors and |V_ub|. A detailed comparison is given with other approaches.Comment: 30 pages+four postscript figures, an Appendix adde

Simultaneous Measurements of Variations in the Artificial Airglow and the Total Electron Content of the Ionosphere Caused by Powerful Radio Waves of "Sura'' Facility

The results of simultaneous observations of variations in the artificial airglow in the red line of the optical spectrum of atomic oxygen (630 nm) and the total electron content (TEC) of the ionosphere measured along the propagation paths of the navigation satellites signal caused by the powerful HF radio emission of ``Sura'' facility on March 12, 2013 have been described in this paper. The observations of the disturbed region structure have allowed a comparison of the position of large-scale inhomogeneities of the electron density and the areas of artificial airglow generation. For comparison of variations in TEC and the artificial airglow, the following steps have been performed: Removing the regular trend brought by satellite motion from the time dependence of TEC; Spatial reference and timing of the night sky portraits received by a CCD camera and drawing of the satellite trajectory on these images; Enhancement of the spots of artificial airglow on the portraits of the night sky; Calculation of the average intensity of airglow from the image area (11 11 pixels) corresponding to the location of the satellite in time of the night sky shooting. Based on the joint analysis of the data, it has been found that the TEC level is decreased for 60% and the intensity of airglow in the red line of the optical spectrum of atomic oxygen is increased for 35% when the pumping wave is turned on. Furthermore, it has been shown that the strongest plasma waves accelerating electrons to the excitation potential of optical levels are generated in the region of low electron concentration as the antenna pattern of ``Sura`` facility is inclined at an angle of to the magnetic zenith. These results will allow applying the corrections to the description of the electron acceleration mechanism up to the levels of optical excitation of atomic oxygen

Development of a Method for Determining the Position of Artificial Ionospheric Irreguliarities Responsible for the Radio-Wave Aspect-Angle Scattering on Short Paths by Oblique Backscatter Sounding Ionograms

The data of experiments on the oblique backscatter sounding of the heated ionospheric volume above the Sura facility on a short Kazan—Vasilsursk—Kazan path, when the Cyclone-GPS ionosonde was operated in the ionogram recording regime in the frequency range 1–7 MHz with a step of about 20 kHz are compared with the results of ray-tracing calculations for the sounding and scattered signals of the O- and X-mode polarizations over the entire range of operating frequencies of the ionosonde. The dependences of the typical transverse (to the geomagnetic field) scales of artificial scattering irregularities (in the range 40–200 m), which are responsible for the aspec-tangle scattering of radio waves of this range, and the position of the scattering region on the frequency of the sounding signals are determined for the entire range of existence of oblique backscatter sounding ionograms

Dynamic Changes of the Ionospheric Artificial Airglow Region Caused by High-Power Radio Waves Based on a Joint Analysis of Night-Sky Snapshots in the 630 nm Line and Total Electron Content Variation Maps

© 2020, Springer Science+Business Media, LLC, part of Springer Nature. We describe a method for joint analysis of the night-sky snapshots and total electron content (TEC) variation maps and present a dynamic spatiotemporal configuration of the TEC variation intensity in the ionospheric airglow region in the red line of atomic oxygen (λ = 630 nm) stimulated by high-power radio waves from the Sura facility. The measurements were performed on the 29th of August, 2016. Two-dimensional TEC variation maps were plotted according to a network of 30 GNSS stations located within a radius of 700 km from the Sura heater. It is shown that the region of the maximum brightness of the artificial ionospheric airglow spot is spatially localized in the region of the minimum intensity of TEC variations, while the region of the maximum intensity of TEC variations corresponds to the region of the minimum brightness of the artificial airglow spot. Quantitative estimates for a cavity with reduced electron density in the artificial airglow region, which forms after the Sura pump wave is switched on, vary in the range ΔNe/Ne ≈ 4–9%, where Ne is the electron density and ΔNe is its variation in the cavity. The proposed experimental technique eliminates the limitations associated with the need for a navigation satellite to flyby directly over the main lobe of the Sura antenna pattern, which significantly increases the chances of successful simultaneous measurements of TEC variations and artificial ionospheric airglow in the 630 nm line

The method of plotting a spatial distribution pattern of the total electron content in the region of artificial airglow of the ionosphere

The method of plotting a spatial distribution pattern of the total electron content (TEC) in the region of artificial airglow of the ionosphere in the red line of the optical spectrum (λ = = 630 nm) was developed during the experiments on disturbances of the ionosphere by powerful radio emission of the SURA facility. To test the method, a measurement session on August 29, 2016 from 18:40 to 20:10 UTC, i.e., when the ionospheric and weather conditions varied slightly and allowed simultaneous optical measurements of the artificial airglow of the ionosphere from two spatially separated sites (Vasilsursk near the SURA facility and Magnitka lying ∼ 170 km East of the SURA facility), was selected. As a result of the simultaneous optical measurements, the area of artificial airglow was plotted in a three-dimensional projection and the spatial position of the disturbed region of the ionosphere stimulated by the powerful radio emission of the SURA facility was determined. The method of plotting a spatial pattern of the electron density distribution in the disturbed region of the ionosphere is based on a joint analysis of variations in the TEC on the radio paths “navigation satellite – ground receiving site” for a number of receiving stations of the global navigation satellite systems located within a radius of ∼ 160 km from the SURA facility. By using this method, the values of electron density variations for different spatial cross-sections of the disturbed region of the ionosphere can be obtained. The joint analysis of the experimental data carried out with the help of the method under consideration showed that in the field of the powerful radio wave a disturbed region with the complex structure formed along the magnetic field lines. Plasma inhomogeneities with an increased electron density occurred at the boundaries of the region with a reduced electron concentration. The difference ∆Ne /Ne at the boundaries of the disturbed region, i.e., between the regions with increased and decreased electron density, might reach 10%. The size of the disturbed region is l⊥ ≈ 45 ÷ 60 km across and l‖ > 70 km along the Earth’s magnetic field lines