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On the application of the effective action approach to amplitudes with reggeon splitting
Application of the effective action approach to amplitudes with loop
integration is studied for collisions on two and three centers with possible
gluon emission. A rule is formulated for the integration around pole
singularities in the induced vertices which brings the results in agreement
with the QCD. It is demonstrated that the amplitudes can be restored from the
purely transverse picture by introducing the standard Feynman propagators for
intermediate gluons and quarks.Comment: 16 pages, 9 figures; submitted to Eur.Phys.Jour.
Diffractive scattering on the deuteron projectile in the NLO: triple interaction of reggeized gluons
High-mass diffractive production of protons on the deuteron target is studied
in the next-to-leading order (NLO) of the perturbative QCD in the BFKL
approach. The non-trivial part of the NLO contributions coming from the triple
interactions of the exchanged reggeons is considered. Analytic formulas are
presented and shown to be infrared free and so ready for practical calculation.Comment: 28 pages, 2 figures; to be published in Eur.Phys.Jour.
Backward asymmetry of the Compton scattering by an isotropic distribution of relativistic electrons: astrophysical implications
The angular distribution of low-frequency radiation after single scattering
by an isotropic distribution of relativistic electrons considerably differs
from the Rayleigh angular function. In particular, the scattering by an
ensemble of ultra-relativistic electrons obeys the law p=1-cos(alpha), where
alpha is the scattering angle; hence photons are preferentially scattered
backwards. We discuss some consequences of this fact for astrophysical
problems. We show that a hot electron-scattering atmosphere is more reflective
than a cold one: the fraction of incident photons which become reflected having
suffered a single scattering event can be larger by up to 50 per cent in the
former case. This should affect the photon exchange between cold accretion
disks and hot coronae or ADAF flows in the vicinity of relativistic compact
objects; as well as the rate of cooling (through multiple inverse-Compton
scattering of seed photons supplied from outside) of optically thick clouds of
relativistic electrons in compact radiosources. The forward-backward scattering
asymmetry also causes spatial diffusion of photons to proceed slower in hot
plasma than in cold one, which is important for the shapes of Comptonization
spectra and the time delays between soft and hard radiations coming from
variable X-ray sources.Comment: 20 pages, 3 figures, to appear in Astronomy Letters, added reference
Polarization of X-ray lines from galaxy clusters and elliptical galaxies - a way to measure tangential component of gas velocity
We study the impact of gas motions on the polarization of bright X-ray
emission lines from the hot intercluster medium (ICM). The polarization
naturally arises from resonant scattering of emission lines owing to a
quadrupole component in the radiation field produced by a centrally peaked gas
density distribution. If differential gas motions are present then a photon
emitted in one region of the cluster will be scattered in another region only
if their relative velocities are small enough and the Doppler shift of the
photon energy does not exceed the line width. This affects both the degree and
the direction of polarization. The changes in the polarization signal are in
particular sensitive to the gas motions perpendicular to the line of sight. We
calculate the expected degree of polarization for several patterns of gas
motions, including a slow inflow expected in a simple cooling flow model and a
fast outflow in an expanding spherical shock wave. In both cases, the effect of
non-zero gas velocities is found to be minor. We also calculate the
polarization signal for a set of clusters, taken from large-scale structure
simulations and evaluate the impact of the gas bulk motions on the polarization
signal. We argue that the expected degree of polarization is within reach of
the next generation of space X-ray polarimeters.Comment: 25 pages, 18 figures, accepted to MNRA
Magnetostimulated Chandges of Microhardness in Potassium Acid Phthalate Crystals
A decrease in microhardness along the (010) cleavage in potassium acid
phthalate single crystals by 15--18% after the application of a permanent
magnetic field was revealed for the first time. It is shown that the effect
revealed is of the volume character. The role of interlayer water in the
processes stimulated by a magnetic field is studied., Interlayer water plays
does not cause the observed changes it only plays the part of an indicator of
these changes in potassium acid phthalate crystals in a magnetic field. It is
established that microhardness in the (100) plane of the crystal in an applied
a magnetic field first increases by 12--15% and then remains constant in time
within the accuracy of the experiment. The possibility of varying the crystal
structure of potassium acid phthalate crystals by applying magnetic fields
inducing rearrangement in the system of hydrogen bonds or in the defect
structure is discussed.Comment: 6 pages, 7 figure
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A Search for Dark Higgs Bosons
Recent astrophysical and terrestrial experiments have motivated the proposal
of a dark sector with GeV-scale gauge boson force carriers and new Higgs
bosons. We present a search for a dark Higgs boson using 516 fb-1 of data
collected with the BABAR detector. We do not observe a significant signal and
we set 90% confidence level upper limits on the product of the Standard
Model-dark sector mixing angle and the dark sector coupling constant.Comment: 7 pages, 5 postscript figures, published version with improved plots
for b/w printin
Monte-Carlo simulations of the broadband X-ray continuum of SS433
We develop a Monte-Carlo technique based on L.B. Lucy's indivisible photon
packets method to calculate X-ray continuum spectra of comptonized thermal
plasma in arbitrary geometry and apply it to describe the broadband X-ray
continuum of the galactic superaccreting microquasar SS433 observed by
INTEGRAL. A physical model of the X-ray emitting region is proposed that
includes thermal emission from the accretion disk, jets and hot corona where
the photons of different origin are comptonized. From comparison with INTEGRAL
observations, we estimate physical parameters of the complex X-ray emitting
region in SS433 and present model spectra for different viewing angles of the
object.Comment: MNRAS accepted. 13 pages, 15 figures, 1 tabl
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