41 research outputs found
Elastic scattering and the proton form factor
We compute the differential and the total cross sections for scattering
using the QCD pomeron model proposed by Landshoff and Nachtmann. This model is
quite dependent on the experimental electromagnetic form factor, and it is not
totally clear why this form factor gives good results even at moderate
transferred momentum. We exchange the eletromagnetic form factor by the
asymptotic QCD proton form factor determined by Brodsky and Lepage (BL) plus a
prescription for its low energy behavior dictated by the existence of a
dynamically generated gluon mass. We fit the data with this QCD inspired form
factor and a value for the dynamical gluon mass consistent with the ones
determined in the literature. Our results also provide a new determination of
the proton wave function at the origin, which appears in the BL form factor.Comment: 10 pages, 2 figures. Submitted to Physics Letters B. Submitted to
Phys. Lett.
Color mixing in high-energy hadron collisions
The color mixing of mesons propagating in a nucleus is studied with the help
of a color-octet Pomeron partner present in the two-gluon model of the Pomeron.
For a simple model with four meson-nucleon channels, color mixings are found to
be absent for pointlike mesons and very small for small mesons. These results
seem to validate the absorption model with two independent color components
used in recent analyses of the nuclear absorption of mesons produced
in nuclear reactions.Comment: 3 journal-style page
Evaluation of Multiloop Diagrams via Lightcone Integration
We present a systematic method to determine the dominant regions of internal
momenta contributing to any two-body high-energy near-forward scattering
diagram. Such a knowledge is used to evaluate leading high-energy dependences
of loop diagrams. It also gives a good idea where dominant multiparticle cross
sections occur.Comment: 14 pages with eight postscript figures; composed in the Revtex
widetext format. This is an expanded and a completely rewritten version
replacing the previous on
On the Gluon Regge Trajectory in
We recalculate the gluon Regge trajectory in next-to-leading order to clarify
a discrepancy between two results in the literature on the constant part. We
confirm the result obtained by Fadin et al.~\cite{FFK}. The effects on the
anomalous dimension and on the behavior of inclusive cross
sections are also discussed.Comment: 8 pages Latex + 1 style file all compressed by uufile
Large Rapidity Gap Processes in Proton-Nucleus Collisions
The cross sections for a variety of channels of proton-nucleus interaction
associated with large gaps in rapidity are calculated within the Glauber-Gribov
theory. We found inelastic shadowing corrections to be dramatically enhanced
for such events. We employ the light-cone dipole formalism which allows to
calculate the inelastic corrections to all orders of the multiple interaction.
Although Gribov corrections are known to make nuclear matter more transparent,
we demonstrate that in some instances they lead to an opaqueness. Numerical
calculations are performed for the energies of the HERA-B experiment, and the
RHIC-LHC colliders.Comment: 19 page
Heavy Quark production at the TEVATRON and HERA using k_t-factorization with CCFM evolution
The application of k_t-factorization supplemented with the CCFM small-x
evolution equation to heavy quark production at the TEVATRON and at HERA is
discussed. The bb_bar production cross sections at the TEVATRON can be
consistently described using the k_t-factorization formalism together with the
unintegrated gluon density obtained within the CCFM evolution approach from a
fit to HERA F_2 data. Special attention is drawn to the comparison with
measured visible cross sections, which are compared to the hadron level Monte
Carlo generator CASCADEComment: 13 pages, updated references and updated Fig. 9, Fig. 2 replace
Probing QCD dynamics in two-photon interactions at high energies
In this paper the two-photon interactions at high energies are investigated
considering different approaches for the QCD dynamics. In particular, we
calculate the total cross section in different theoretical
approches and present a comparison among the predictions of the BFKL dynamics
at leading and next-to-leading order with those from saturation physics. We
analyze the possibility that the future linear colliders could discriminate
between these different approaches.Comment: 14 pages, 2 figures. Version to be published in Journal of Physics G:
Nuclear and Particle Physic
Shadowing of gluons in perturbative QCD: A comparison of different models
We investigate the different perturbative QCD-based models for nuclear
shadowing of gluons. We show that in the kinematic region appropriate to RHIC
experiment, all models give similar estimates for the magnitude of gluon
shadowing. At scales relevant to LHC, there is a sizable difference between
predictions of the different models.Comment: 11 pages, 4 figure
Photoproduction of J/psi mesons at high energies in parton model and k_t-faktorization approach
We consider J/psi meson photoproduction on protons at high energies at the
leading order in alpha_s using conventional parton model and k_t-factorization
approach of QCD. It is shown that in the both cases the colour singlet
mechanism gives correct description for experimental data from HERA for the
total cross section and for the J/psi meson z-spectrum at realistic values of a
c-quark mass and meson wave function at the origin Psi (0). At the same time
our predictions for p_t-spectrum of J/psi meson and for p_t dependence of the
spin parameter alpha obtained in k_t-factorization approach are very different
from the results obtained in conventional parton model. Such a way the
experimental study of a polarized J/psi meson production at the large p_t
should be a direct test of BFKL gluons.Comment: LaTeX2e, 11 pages plus 8 fig. using epsfig.st
kt - factorization and CCFM - the solution for describing the hadronic final states - everywhere ?
The basic ideas of kt-factorization and CCFM parton evolution is discussed.
The unintegrated gluon densities, obtained from CCFM fits to the proton
structure function data at HERA are used to predict hadronic final state cross
sections like jet production at HERA, but also comparisons with recent
measurements of heavy quark production at the Tevatron are presented. Finally,
the kt-factorization approach is applied to Higgs production at high energy
hadron hadron colliders and the transverse momentum spectrum of Higgs
production at the LHC is calculated.Comment: to be published in MPLA, replaced with new reference