4,050 research outputs found

    Solar cycle influence on the interaction of the solar wind with Local Interstellar Cloud

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    We present results of a new time-dependent kinetic model of the H atom penetration through the solar wind - interstellar medium interaction region. A kinetic 6D (time, two dimensions in space, and three dimensions in velocity-space) equation for interstellar H atoms was solved self-consistently with time-dependent Euler equations for the solar wind and interstellar charged components. We study the response of the interaction region to 11-year solar cycle variations of the solar wind dynamic pressure. It is shown that the termination shock location varies within ±7 AU, the heliopause variation is ~4 AU, and the bow shock variation is negligible. At large heliocentric distances, the solar cycle induces 10-12% fluctuations in the number density of both primary and secondary interstellar H atoms and atoms created in the inner heliosheath. We underline the kinetic behavior of the fluctuations of the H atom populations. Closer to the Sun the fluctuations increase up to 30-35% at 5 AU due to solar cycle variation of the charge exchange rate. Solar cycle variations of interstellar H atoms in the heliospheric interface and within the heliosphere may have major importance for the interpretation of H atom observations inside the heliosphere

    Measurement of XeI and XeII velocity in the near exit plane of a low-power Hall effect thruster by light induced fluorescence spectroscopy

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    Near exit plane non-resonant light induced fluorescence spectroscopy is performed in a Hall effect low-power Xenon thruster at discharge voltage of 250V and anode flow rate of 0.7mg/sec. Measurement of the axial and radial velocity components are performed, exciting the 6s[3/2]_2-->6p[3/2]_2 transition at 823.16nm in XeI and the 5d[4]_(7/2)-->6p[3]_(5/2) transition at 834.724nm in XeII. No significant deviation from the thermal velocity is observed for XeI. Two most probable ion velocities are registered at a given position with respect to the thruster axis, which are mainly attributed to different areas of creation of ions inside the acceleration channel. The spatial resolution of the set-up is limited by the laser beam size (radius of the order of 0.5mm) and the fluorescence collection optics, which have a view spot diameter of 8mm.Comment: 6 pages, 8 figure

    Extracts from Problems of Air Law, a collection of works of the Section of air law of the Aviakhim Society of the USSR and Aviakhim RSFSR

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    The difficulties of developing a body of international law to govern air travel is discussed. A summary of literature and agreements is presented as well as a brief history. Air space over the poles and the legality of methods of claiming territory in the polar regions is discussed

    Production of electroweak gauge bosons in off-shell gluon-gluon fusion

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    We study the production of electroweak gauge bosons at high energies in the framework of kt-factorization QCD approach. Contributions from the valence quarks are calculated using the quark-gluon interaction and quark-antiquark annihilation QCD subprocesses. The total and differential cross sections (as a function of the transverse momentum and rapidity) are presented and the ratio of cross sections for W and Z boson production is investigated. The conservative error analysis is performed. In the numerical calculations two different sets of unintegrated gluon distributions in the proton are used: the one obtained from Ciafaloni-Catani-Fiorani-Marchesini evolution equation and the other from Kimber-Martin-Ryskin prescription. Theoretical results are compared with experimental data taken by the D0 and CDF collaborations at the Tevatron. We demonstrate the importance of the quark component in parton evolution in description of the experimental data. This component is very significant also at the LHC energies.Comment: 33 pages, 18 figure

    Prompt photon hadroproduction at high energies in off-shell gluon-gluon fusion

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    The amplitude for production of a single photon associated with quark pair in the fusion of two off-shell gluons is calculated. The matrix element found is applied to the inclusive prompt photon hadroproduction at high energies in the framework of kt-factorization QCD approach. The total and differential cross sections are calculated in both central and forward pseudo-rapidity regions. The conservative error analisys is performed. We used the unintegrated gluon distributions in a proton which were obtained from the full CCFM evolution equation as well as from the Kimber-Martin-Ryskin prescription. Theoretical results were compared with recent experimental data taken by the D0 and CDF collaborations at Fermilab Tevatron. Theoretical predictions for the LHC energies are given.Comment: 32 pages, 18 figure

    Laser cooling of a trapped two-component Fermi gas

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    The collective Raman cooling of a trapped two-component Fermi gas is analyzed. We develop the quantum master equation that describes the collisions and the laser cooling, in the festina lente regime, where the heating due to photon reabsorption can be neglected. The numerical results based on Monte Carlo simulations show, that three-dimensional temperatures of the order of 0.008 T_F can be achieved. We analyze the heating related to the background losses, and conclude that our laser-cooling scheme can maintain the temperature of the gas without significant additional losses. Finally we derive an analytic expression for the temperature of a trapped Fermi gas heated by background collisions, that agrees very well with the data obtained from the numerical simulation.Comment: 5 pages, 3 figure

    Pion Interferometry for Hydrodynamical Expanding Source with a Finite Baryon Density

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    We calculate the two-pion correlation function for an expanding hadron source with a finite baryon density. The space-time evolution of the source is described by relativistic hydrodynamics and the Hanbury-Brown-Twiss (HBT) radius is extracted after effects of collective expansion and multiple scattering on the HBT interferometry have been taken into account, using quantum probability amplitudes in a path-integral formalism. We find that this radius is substantially smaller than the HBT radius extracted from the freeze-out configuration.Comment: 4 pages, 2 figure

    Pairing collectivity in medium-mass neutron-rich nuclei near drip-line

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    We look for collective excitations originating from the strong surface pairing in unstable nuclei near the neutron drip-line. The soft dipole excitation is such a pairing mode as it exhibits a character of core-vs-dineutron motion. Possibility of the hydrodynamic phonon mode (the Anderson-Bogoliubov mode) is also discussed.Comment: 9 pages, a talk presented at Collective Motion in Nuclei under Extreme Conditions (COMEX2), June 20-23, 2006, St. Goar, German

    Polarizations of J/\psi and \psi' in hadroproduction at Tevatron in the k_t factorization approach

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    We present a calculation for the polarizations of J/ψJ/\psi and ψ\psi' produced in the hadron collisions at the Fermilab Tevatron. Various color octet channels including 1S0(8){}^1S_0^{(8)}, 3PJ(8){}^3P_J^{(8)}, and 3S1(8){}^3S_1^{(8)} as well as contributions from χcJ\chi_{cJ} decays are considered in the ktk_t factorization approach. We find that in a rather wide range of the transverse momenta of J/ψJ/\psi and ψ\psi', the production rates could be dominated by the 1S0(8){}^1S_0^{(8)} channel, and the predicted polarizations from the 1S0(8){}^1S_0^{(8)} channel and χcJ\chi_{cJ} feeddown contributions are roughly compatible with the preliminary CDF data. This might provide a possible release from the conflict between the NRQCD collinear parton model calculations and the CDF data.Comment: 12 pages, 4 PS files, final version for publicatio
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