668 research outputs found
Sensitivity of depth of maximum and absorption depth of EAS to hadron production mechanism
Comparison of experimental data on depth of extensive air showers (EAS) development maximum in the atmosphere, T sub M and path of absorption, lambda, in the lower atmosphere of EAS with fixed particle number in the energy region eV with the results of calculation show that these parameters are sensitive mainly to the inelastic interaction cross section and scaling violation in the fragmentation and pionization region. The data are explained in a unified manner within the framework of a model in which scaling is violated slightly in the fragmentation region and strongly in the pionization region at primary cosmic rays composition close to the normal one and a permanent increase of inelastic interaction cross section. It is shown that, while interpreting the experimental data, disregard of two methodical points causes a systematic shift in T sub M: (1) shower selection system; and (2) EAS electron lateral distribution when performing the calculations on basis of which the transfer is made from the Cerenkov pulse FWHM to the depth of shower maximum, T sub M
Relativistic Description of Exclusive Semileptonic Decays of Heavy Mesons
Using quasipotential approach, we have studied exclusive semileptonic decays
of heavy mesons with the account of relativistic effects. Due to more complete
relativistic description of the quark more precise expressions for
semileptonic form factors are obtained. Various differential distributions in
exclusive semileptonic decays of heavy mesons are calculated. It is argued that
consistent account of relativistic effects and HQET motivated choice of the
parameters of quark-antiquark potential allow to get reliable value for the
ratio in the decay as well as the
ratio~. All calculated branching
ratios are in accord with available experimental data.Comment: 18 pages, LATEX, 2 figures inclosed + 4 Postscript figure
Properties of heavy quarkonia and B_c mesons in the relativistic quark model
The mass spectra and electromagnetic decay rates of charmonium, bottomonium
and B_c mesons are comprehensively investigated in the relativistic quark
model. The presence of only heavy quarks allows the expansion in powers of
their velocities. All relativistic corrections of order v^2/c^2, including
retardation effects and one-loop radiative corrections, are systematically
taken into account in the computations of the mass spectra. The obtained wave
functions are used for the calculation of radiative magnetic dipole (M1) and
electric dipole (E1) transitions. It is found that relativistic effects play a
substantial role. Their account and the proper choice of the Lorentz structure
of the quark-antiquark interaction in a meson is crucial for bringing
theoretical predictions in accord with experimental data. A detailed comparison
of the calculated decay rates and branching fractions with available
experimental data for radiative decays of charmonium and bottomonium is
presented. The possibilities to observe the currently missing spin-singlet S
and P states as well as D states in bottomonium are discussed. The results for
B_c masses and decays are compared with other quark model predictions.Comment: 31 pages, 2 figures, minor correction
Synthesis, structure, and biologic activity of products of reactions between dinitrodichlorobenzofuroxane and aminopyrimidines in aqueous dimethyl sulfoxide
© 2016, Pleiades Publishing, Ltd.Reactions of 4,6-dinitro-5,7-dichlorobenzofuroxane with substituted pyrimidines in aqueous DMSO proceed through an intermediate formation of 5-hydroxy-4,6-dinitro-7-chlorobenzofuroxane owing to the hydrolysis of one of the chlorine atoms with the subsequent formation of pyrimidine salts exhibiting a high biologic action
Relativistic description of heavy tetraquarks
The masses of the ground state and excited heavy tetraquarks with hidden
charm and bottom are calculated within the relativistic diquark-antidiquark
picture. The dynamics of the light quark in a heavy-light diquark is treated
completely relativistically. The diquark structure is taken into account by
calculating the diquark-gluon form factor. New experimental data on
charmonium-like states above the open charm threshold are discussed. The
obtained results indicate that X(3872), Y(4260), Y(4360), Z(4433) and Y(4660)
can be tetraquark states with hidden charm.Comment: 6 pages, talk at the scientific session-conference of Nuclear Physics
Department RAS ``Physics of fundamental interactions'', 25-30 November 2007,
ITEP, Mosco
Exclusive semileptonic B decays to radially excited D mesons
Exclusive semileptonic B decays to radially excited charmed mesons are
investigated at the first order of the heavy quark expansion. The arising
leading and subleading Isgur-Wise functions are calculated in the framework of
the relativistic quark model. It is found that the 1/m_Q corrections play an
important role and substantially modify results. An interesting interplay
between different corrections is found. As a result the branching ratio for the
B-> D'e\nu decay is essentially increased by 1/m_Q corrections, while the one
for B-> D*'e\nu is only slightly influenced by them.Comment: 19 pages, revtex, 6 figures, uses rotating.st
Searching for the Layered Structure of Space at the LHC
Alignment of the main energy fluxes along a straight line in a target plane
has been observed in families of cosmic ray particles detected in the Pamir
mountains. The fraction of events with alignment is statistically significant
for families with superhigh energies and large numbers of hadrons. This can be
interpreted as evidence for coplanar hard-scattering of secondary hadrons
produced in the early stages of the atmospheric cascade development. This
phenomenon can be described within the recently proposed "crystal world," with
latticized and anisotropic spatial dimensions. Planar events are expected to
dominate particle collisions at a hard-scattering energy exceeding the scale
\Lambda_3 at which space transitions from 3D \rightleftharpoons 2D. We study
specific collider signatures that will test this hypothesis. We show that the
energy-spectrum of Drell-Yan scattering and the parton momenta sum rule are
significantly modified in this framework. At the LHC, two jet and three jet
events are necessarily planar, but four jet events can test the hypothesis.
Accordingly, we study in a model-independent way the 5\sigma discovery reach of
the ATLAS and CMS experiments for identifying four jets coplanarities. For the
extreme scenario in which all pp \to 4 jet scattering processes become coplanar
above \Lambda_3, we show that with an integrated luminosity of 10(100) fb^{-1}
the LHC experiments have the potential to discover correlations between jets if
\Lambda_3 \alt 1.25(1.6) TeV.Comment: To be published in Phys. Rev.
5-Amino-Substituted Derivatives of 4-Nitrofurazane: Synthesis, Structure, and Biological Activity
© 2018, Pleiades Publishing, Ltd. New amination reactions of 5-chloro-4-nitrobenzofurazane with different amines were studied. The reactions of 5-chloro-4-nitrobenzofurazane with 2,4,6-trichloro-, para-acetyl-, and para-carboxyethylanilines gave the products of aromatic nucleophilic substitution of the chlorine substituent in the nitrogenous heterocycle, the composition and structure of which was established by chemical, physical, and physicochemical methods and X-ray diffraction analysis. The thermal stability was studied by synchronous thermogravimetry and differential scanning calorimetry (TG‒DSC). The synthesized compounds showed a high antibacterial and antimycotic activity against human and animal pathogenic microflora
KINETICS OF GELATIN HARDENING BY CERTAIN ALDEHYDE AND EPOXY HARDENERS IN CONCENTRATED MEDIA.
Study of the influence of gelatin concentration on the rate of its hardening by hardeners differing in activity showed that in the case of highly reactive hardeners in concentrated solutions the process is controlled by diffusion and the reaction rate falls sharply. In the case of hardeners of low reactivity the reaction rate is independent of concentration. The results obtained provide a link between the kinetic parameters of gelatin hardening in dilute and concentrated solutions, making it possible to calculate the time required for any specified degree of hardening in solutions of any concentration
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