180 research outputs found
Intrinsic Charm In Proton and Photoproduction at High Energies
Based on a perturbative theory of quantum chromodynamics and non-relativistic
quark model, associated plus open charm photoproduction on charm
quarks in a proton via partonic subprocess is discussed.
It is shown that the value and energy dependence of the cross section for such
process remarkably depends on the choice of charm distribution function in a
proton. In the region of small the contribution of the
subprocess in the inelastic photoproduction
spectra is larger than the contribution of the photon-gluon fusion subprocess.
At the energy range of HERA collider intrinsic charm contribution in the total
inclusive photoproduction cross section may be equal to 4\% of the
dominant contribution of photon-gluon fusion mechanism.Comment: 11 pages, submitted to Mod.Phys.Lett.
Lambda_b polarization in the Z boson decays
In the framework of the perturbative QCD and the diquark model of baryons we
have obtained the fragmentation functions for heavy quark that split into
polarized Lambda_b baryons. We predict the longitudinal polarization asymmetry
for the prompt Lambda_b produced in electron-positron annihilation at the Z
resonance and estimate the spin-1/2 and spin-3/2 beauty baryon production rate.Comment: LaTeX, 8 pages plus 6 figures using psfig.st
and hadroproduction in the parton Reggeization approach: Yield, polarization, and the role of fragmentation
The hadroproduction of the radially excited heavy-quarkonium states
and at high energies is studied in the parton
reggeization approach and the factorization formalism of nonrelativistic QCD at
lowest order in the strong-coupling constant and the relative
heavy-quark velocity . A satisfactory description of the
transverse-momentum () distributions measured by ATLAS, CMS, and LHCb at
center-of-mass energy TeV is obtained using the color-octet
long-distance matrix elements (LDMEs) extracted from CDF data at
TeV. The importance of the fragmentation mechanism and the
scale evolution of the fragmentation functions in the upper range, beyond
30 GeV, is demonstrated. The distributions measured by CDF
at TeV and by LHCb at TeV and forward rapidities
are well described using LDMEs fitted to ATLAS data at TeV.
Comparisons of polarization measurements by CDF and CMS at large values
with our predictions consolidate the familiar problem in the case,
but yield reasonable agreement in the case.Comment: 28 pages, 12 figures, minor text additions, references added, matches
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