152 research outputs found
Production of -mesons in proton-proton and proton-nucleus interactions at various energies
The experimental data on the production of -mesons in pp-collisions are
analyzed and a method of the unified description of these data in a broad
energy range for primary protons is proposed. The -mesons production in
pA-collisions is considered. The simple formulas for inclusive cross sections
of the production in these collisions are given. The results of the
calculations by these formulas are compared with the available experimental
data.Comment: 14 pages, LaTeX, uses ws-art.sty. Figures can be requested from
[email protected] or looked up in the article abov
Subthreshold Production on Nuclei by Mesons
The inclusive mesons production in --nucleus reactions in the
subthreshold energy regime is analyzed with respect to the one--step
() and the two--step () incoherent production processes on the basis of an appropriate
folding model, which allows one to take into account the various forms of an
internal nucleon momentum distribution as well as on-- and off--shell
propagation of the struck target nucleon. Contrary to proton--nucleus reactions
primary reaction channel is found to be significant practically at all
considered energies. Detailed predictions for the total and invariant
differential cross sections from \piC-- and \piPb--collisions at subthreshold
energies are provided.Comment: 18 pages, LaTeX, uses ws-art.sty, gzip+uuencoded postscript. Figures
are available by request from [email protected]
Subthreshold K+ Meson Production in Proton-Nucleus Reactions
The inclusive K+ mesons production in proton-nucleus collisions in the near
threshold and subthreshold energy regimes is analyzed with respect to the
one-step (pN->K+YN, Y=Lambda,Sigma) and the two-step (pN->NNpi, NN2pi;
piN->K+Y) incoherent production processes on the basis of an appropriate new
folding model, which takes properly into account the struck target nucleon
removal energy and momentum distribution (nucleon spectral function), extracted
from recent quasielastic electron scattering experiments and from many-body
calculations with realistic models of the NN interaction. Comparison of the
model calculations of the K+ double differential cross sections for the
reaction p+C at 1.2, 1.5 and 2.5 GeV beam energies with the existing
experimental data from the SATURNE experiment is given, illustrating both the
relative role of the primary and secondary production channels at considered
incident energies and those features of the cross sections which are sensitive
to the high momentum and high removal energy part of the nucleon spectral
function that is governed by nucleon-nucleon short-range and tensor
correlations. In--medium modifications of the available for pion and hyperon
production invariant energies squared due to the respective optical potentials
are needed to account for the experimental data on K+ production in the energy
region under consideration.Comment: 6 pages, LaTeX, uses revtex.st
Study of correlation of production and decay planes in diffractive dissociation process on nuclei
A large correlation of production and decay planes of
(\pi^-\pi^+\pi^-)-system in dissociation of -beam 40 GeV/c on nuclear
targets was observed. The dependence of the correlation on atomic number,
Feynmann variable and transversal momentum as well as on invariant mass of the
pion triple and neutral pion pair were investigated. It was shown that the
phenomenon has a clear dynamic origin and resembles the single spin asymmetry
behavior.Comment: 8 pages, latex epsfig.sty, 5 eps figures. Submitted to Yad. Fiz
The ratio in heavy-quark pair leptoproduction as a probe of linearly polarized gluons in unpolarized proton
We study the Callan-Gross ratio in
heavy-quark pair leptoproduction, , as a
probe of linearly polarized gluons inside unpolarized proton, where () is the differential cross section of the
process initiated by a transverse
(longitudinal) virtual photon. Note first that the maximal value for the
quantity allowed by the photon-gluon fusion with unpolarized gluons is
large, about 2. We calculate the contribution of the transverse-momentum
dependent gluonic counterpart of the Boer-Mulders function, ,
describing the linear polarization of gluons inside unpolarized proton. Our
analysis shows that the maximum value of the ratio depends strongly on the
gluon polarization; it varies from 0 to depending on
. We conclude that the Callan-Gross ratio in heavy-quark pair
leptoproduction is predicted to be large and very sensitive to the contribution
of linearly polarized gluons. For this reason, future measurements of the
longitudinal and transverse components of the charm and bottom production cross
sections at the proposed EIC and LHeC colliders seem to be very promising for
determination of the linear polarization of gluons inside unpolarized proton.Comment: 8 pages, 4 figures, journal version. arXiv admin note: substantial
text overlap with arXiv:1711.0522
On the T-Odd Quark Fragmentation Function and on Transversal Handedness
The first probe of the correlation of the T-odd one-particle fragmentation
function responsible for the left--right asymmetry of fragmentation of a
transversely polarized quark is done by using the 1991-95 DELPHI data for -jet decay. Integrated over the fraction of longitudinal and transversal
momenta, this correlation is of 1.5% order, which means order of 13% for the
analyzing power.
A rather large () handedness transversal to the production plane
was observed in the diffractive production of () triples from
nuclei by the --beam. It was shown that the phenomenon has a
clear dynamic origin and resembles the single spin asymmetry behavior. All this
makes us hope to use this effects in polarized DIS experiments for transversity
measurement.Comment: 10 pp, 5 epsfig, Latex 2e, szjp.cls, epsfig.sty, wrapfig.sty
included. Talk in "Spin and Symmetry - Praha98". To be published in
Czechoslovak Journal of Physics, Supp
The Role of Carbonized Layers for Fire Protection of Polymer Materials
The present work studies the processes occurring in pre-flame zone in the form of «candle-like flame» which is spread over the surface of epoxy polymer. As exemplified by epoxy polymer, it can be seen that the dominating mechanism of heat transfer from flame to pre-flame zone of carbonized polymers is a thermal conductivity by condensed phase (to phase). The mechanism of gasification processes in pre-flame zone is proposed. Gasification of the material in front of the flame edge is a controlling process, and when selecting flame retardants, it is necessary to register their ability to influence on kinetics and mechanism of gasification. The flame leading edge is bordered with the surface of polymer, which largely determines the nature of heat transfer in pre-flame region. Due to investigations of gas-phase composition at «candle-like» combustion of epoxy polymer it has been detected a considerable amount of oxygen (up to 10‒12%) near burning surface. Its presence facilitates the thermal oxidation of polymer, moreover the rate of thermal oxidation can significantly exceed the thermal decomposition rate of the polymer. The possibility to form the heat-insulating intumescent layer during decomposition of carbonizable polymers was used at development of flame retardant coatings ‒ complex multicomponent systems. Which in turns forms the intumescent carbonized layer with high porosity and low thermal conductivity, and protects based material or construction from premature heating up to critical temperatures
Variation in nuclear genome size within the Eisenia nordenskioldi complex (Lumbricidae, Annelida)
The size of the nuclear genome in eukaryotes is mostly determined by mobile elements and noncoding sequences and may vary within wide limits. It can differ significantly both among higher-order taxa and closely related species within a genus; genome size is known to be uncorrelated with organism complexity (the so-called C-paradox). Less is known about intraspecific variation of this parameter. Typically, genome size is stable within a species, and the known exceptions turn out be cryptic taxa. The Eisenia nordenskioldi complex encompasses several closely related earthworm species. They are widely distributed in the Urals, Siberia, and the Russian Far East, as well as adjacent regions. This complex is characterized by significant morphological, chromosomal, ecological, and genetic variation. The aim of our study was to estimate the nuclear genome size in several genetic lineages of the E. nordenskioldi complex using flow cytometry. The genome size in different genetic lineages differed strongly, which supports the hypothesis that they are separate species. We found two groups of lineages, with small (250–500 Mbp) and large (2300–3500 Mbp) genomes. Moreover, different populations within one lineage also demonstrated variation in genome size (15–25 %). We compared the obtained data to phylogenetic trees based on transcriptome data. Genome size in ancestral population was more likely to be big. It increased or decreased independently in different lineages, and these processes could be associated with changes in genome size and/or transition to endogeic lifestyle
Absorption of phi mesons in near-threshold proton-nucleus reactions
In the framework of the nuclear spectral function approach for incoherent
primary proton--nucleon and secondary pion--nucleon production processes we
study the inclusive meson production in the interaction of 2.83 GeV
protons with nuclei. In particular, the A-dependences of the absolute and
relative meson yields are investigated within the different scenarios
for its in-medium width as well as for the cross section ratio . Our model calculations take into account
the acceptance window of the ANKE facility used in a recent experiment
performed at COSY. They show that the pion--nucleon production channel
contributes distinctly to the creation in heavy nuclei in the chosen
kinematics and, hence, has to be taken into consideration on close examination
of the dependences of the phi meson yields on the target mass number with the
aim to get information on its width in the medium. They also demonstrate that
the experimentally unknown ratio has a weak effect on the A-dependence of the relative meson
production cross section at incident energy of present interest, whereas it is
found to be appreciably sensitive to the phi in-medium width, which means that
this relative observable can indeed be useful to help determine the above width
from the direct comparison the results of our calculations with the future data
from the respective ANKE-at-COSY experiment.Comment: 16 pages, 9 figure
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