4,848 research outputs found
Heavy quark production in the semihard QCD approach at THERA
In the framework of the semihard ( factorization) QCD approach, we
consider the photoproduction of D* mesons associated with two hadron jets and
the D* production in DIS at THERA conditions with the emphasis on the BFKL and
CCFM dynamics of gluon distributions. In the photoproduction of D* mesons the
attention is focused on the variable , which is the fraction of the
photon momentum contributed to a pair of jets with largest . We show that
our theoretical results are sensitive to the BFKL type dynamics which may be
investigated at THERA energies. We also discuss possible effect of \J/\psi
meson spin alignement, which is thought to be a vivid manifestation of gluon
off-shellness.Comment: 9 pages, 3 figures, in "The THERA Book", DESY-LC-REV-2001-06
Prompt meson production at the LHC in the NRQCD with -factorization
In the framework of the -factorization, the prompt production of
mesons at the LHC conditions is studied. Our consideration is based on
the off-shell amplitudes for hard partonic subprocesses and on the
nonrelativistic QCD (NRQCD) formalism for the formation of bound states. We try
two latest parametrizations for noncollinear, or transverse momentum dependent
(TMD) gluon densities derived from the Catani-Ciafaloni-Fiorani-Marchesini
(CCFM) equation. We use the values of the nonperturbative matrix elements
obtained from a combined fit of the and differential cross
sections. Finally, we show an universal set of parameters that provides a
reasonable simultaneous description for all of the available data on the prompt
and production at the LHC.Comment: 5 pages, 2 figures, 3 table
Prompt charmonia production and polarization at LHC in the NRQCD with -factorization. Part III: meson
In the framework of -factorization approach, the production and
polarization of prompt mesons at the LHC energies is studied. Our
consideration is based on the non-relativistic QCD formalism for bound states
and off-shell amplitudes for hard partonic subprocesses. Both the direct
production mechanism and feed-down contributions from and
decays are taken into account. The transverse momentum dependent (or
unintegrated) gluon densities in a proton were derived from
Ciafaloni-Catani-Fiorani-Marchesini evolution equation or, alternatively, were
chosen in accordance with Kimber-Martin-Ryskin prescription. The
non-perturbative color-octet matrix elements were first deduced from the fits
to the latest CMS data on transverse momentum distributions and then
applied to describe the ATLAS and LHCb data on production and
polarization at , and TeV. We perform an estimation of
polarization parameters , and which determine spin density matrix and demonstrate that
treating the soft gluon emission as a series of explicit color-electric dipole
transitions within NRQCD leads to unpolarized production at high
transverse momenta, that is in qualitative agreement with the LHC data.Comment: 23 pages, 14 figures. arXiv admin note: substantial text overlap with
arXiv:1508.0548
First estimates of the wave function from the data on the production cross section
In the framework of perturbative QCD and nonrelativistic bound state
formalism, we calculate the production of and mesons at the
conditions of the CDF and LHCb experiments. We derive first estimations for the
wave function from a comparison with the available data.Comment: 3 pages, 1 figur
Fragmentation of charm to charmonium in and collisions
We perform numerical comparison of the fragmentation mechanism of charmonium
production ( followed by ) with the full
leading order calculation ( at {\O} (\alpha_s^4)).
We conclude that the non-fragmentation contributions remain important up to
transverse momenta about as large as 50 GeV, thus making questionable
the applicability of the fragmentation approximation at smaller transverse
momenta.Comment: 6 pages, 7 figure
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