199 research outputs found
Double vector meson production from the BFKL equation
The double vector meson production in two photon collisions is addressed
assuming that the color singlet -channel exchange carries large momentum
transfer. We consider the non-forward solution of the BFKL equation at high
energy and large momentum transfer and estimate the total and differential
cross section for the process , where and
can be any two vector mesons (). A comparison between our predictions and previous theoretical
results obtained at Born level or assuming the Pomeron-exchange factorization
relations is presented. Our results demonstrate that the BFKL dynamics implies
an enhancement of the cross sections. Predictions for the future linear
colliders (TESLA, CLIC and ILC) are given.Comment: 13 pages, 3 tables, 7 figures. Minor changes. Accepted for
publication in Eur. Phys. J.
Charm photoproduction at HERA: kt-factorization versus experimental data
We calculate the cross section of charm photoproduction at HERA collider in
the framework of the kt-factorization QCD approach. Our analysis cover the
inclusive charm production as well as charm and associated jet production
processes. Both photon-gluon and gluon-gluon fusion mechanisms are taken into
account. The unintegrated gluon densities in a proton and in a photon obtained
from the full CCFM, from unified BFKL-DGLAP evolution equations as well as from
the Kimber-Martin-Ryskin prescription are used. Our theoretical results are
compared with the recent experimental data taken by the H1 and ZEUS
collaborations at HERA. Special attention is put on the specific angular
correlations which can provide unique information about non-collinear gluon
evolution dynamics.Comment: 33 pages, 15 figures, 2 table
Prompt photon photoproduction at HERA in the k_T-factorization approach
We present calculations of the prompt photon photoproduction at HERA collider
in the k_T-factorization approach. Both direct and resolved contributions are
taken into account. The conservative error analisys is performed. The
unintegrated parton densities in a proton and in a photon are determined using
the Kimber-Martin-Ryskin prescription. We investigate both inclusive and
associated with jet prompt photon photoproduction rates. In particular, we
study the angular correlations between produced photon and hadronic jet in the
transverse momentum plane which can provide a unique information about
non-collinear evolution dynamics. We compare our theoretical predictions with
recent experimental data taken by the H1 and ZEUS collaborations.Comment: 34 pages, 18 figure
Nuclear charm and bottom production: a comparison among high energy approaches
We calculate the nucleon and nuclear photoproduction cross sections for heavy
quarks within the -factorization formalism, considering the current
high energy approaches which include nuclear and saturation effects. Our
results demonstrate that a future experimental analysis of this process would
allow to constraint the QCD dynamics at high energies.Comment: 10 pages, 2 figures. Version to be published in Eur. Phys. J.
Double diffractive meson production and the BFKL Pomeron at colliders
In this Letter we study the double diffractive vector meson production in
collisions assuming the dominance of the BFKL pomeron exchange. We
consider the non-forward solution of the BFKL equation at high energy and large
momentum transfer and estimate the total cross section for the process with antitagged and , where and can
be any two vector mesons (). The
event rates for the future linear colliders are given.Comment: 8 pages, 1 figure, Version to be published in Physical Review
Beauty photoproduction at HERA: kt-factorization versus experimental data
We present calculations of the beauty photoproduction at HERA collider in the
framework of the kt-factorization approach. Both direct and resolved photon
contributions are taken into account. The unintegrated gluon densities in a
proton and in a photon are obtained from the full CCFM, from unified BFKL-DGLAP
evolution equations as well as from the Kimber-Martin-Ryskin prescription. We
investigate different production rates (both inclusive and associated with
hadronic jets) and compare our theoretical predictions with the recent
experimental data taken by the H1 and ZEUS collaborations. Special attention is
put on the x_{\gamma}^{obs} variable which is sensitive to the relative
contributions to the beauty production cross section.Comment: 29 pages, 15 figures, 2 table
Исследование влияния технологических факторов на высоту элементов шрифта Брайля
У статті досліджено вплив технологічних режимів тиснення і характеристик матеріалів на формування елементів шрифту Брайля.Experimental researches of the influence of the pressure value on the formation of elements of the Braille type on different cardboards are conducted.В статье исследуется влияние технологических режимов тиснения и характеристик материалов на формирование элементов шрифта Брайля
Spin Effects in Two Quark System and Mixed States
Based on the numeric solution of a system of coupled channels for vector
mesons (- and -waves mixing) and for tensor mesons (- and -waves
mixing) mass spectrum and wave functions of a family of vector mesons
in triplet states are obtained. The calculations are performed using
a well known Cornell potential with a mixed Lorentz-structure of the
confinement term. The spin-dependent part of the potential is taken from the
Breit-Fermi approach. The effect of singular terms of potential is considered
in the framework of the perturbation theory and by a configuration interaction
approach (CIA), modified for a system of coupled equations. It is shown that
even a small contribution of the -wave to be very important at the
calculation of certain characteristics of the meson states.Comment: 12 pages, LaTe
The QCD Pomeron in ultraperipheral heavy ion collisions: III. Photonuclear production of heavy quarks
We calculate the photonuclear production of heavy quarks in ultraperipheral
heavy ion collisions. The integrated cross section and the rapidity
distribution are computed employing sound high energy QCD formalisms as the
collinear and semihard approaches as well as the saturation model. In
particular, the color glass condensate (CGC) formalism is also considered using
a simple phenomenological parameterization for the color field correlator in
the medium, which allow us to obtain more reliable estimates for charm and
bottom production at
LHC energies.Comment: 15 pages, 2 figures. Extended version to be published in Eur. Phys.
J.
Heavy quark and quarkonium production at CERN LEP2: k_T-factorization versus data
We present calculations of heavy quark and quarkonium production at CERN LEP2
in the k_T-factorization QCD approach. Both direct and resolved photon
contribution are taken into account. The conservative error analisys is
performed. The unintegrated gluon distribution in the photon is taken from the
full CCFM evolution equation. The traditional color-singlet mechanism to
describe non-perturbative transition of heavy quark pair into a final
quarkonium is used. Our analisys covers polarization properties of heavy
quarkonia at moderate and large transverse momenta. We find that the total and
differential open charm production cross sections are consistent with the
recent experimental data taken by the L3, OPAL and ALEPH collaborations. At the
same time the DELPHI data for the inclusive J/Psi production exceed our
predictions but experimental uncertainties are too large to claim a significant
inconsistency. The bottom production in photon-photon collisions at CERN LEP2
is hard to explain within the k_T-factorization formalism.Comment: 25 pages, 11 figure
- …