672 research outputs found
Prompt photon hadroproduction at high energies in the k_T-factorization approach
We consider the prompt photon production at high energy hadron colliders in
the framework of k_T-factorization approach. The unintegrated quark and gluon
distributions in a proton are determined using the Kimber-Martin-Ryskin
prescription. The conservative error analisys is performed. We investigate both
inclusive prompt photon and prompt photon and associated muon production rates.
In Standard Model such events come mainly due to Compton scattering process
where the final heavy (charm or bottom) quark produces a muon. The theoretical
results are compared with recent experimental data taken by the D0 and CDF
collaborations at Fermilab Tevatron. Our analysis also covers the azimuthal
correlations between produced prompt photon and muon which can provide an
important information about non-collinear parton evolution in a proton.
Finally, we extrapolate the theoretical predictions to CERN LHC energies.Comment: 27 pages, 13 figure
Baxter Equation for the QCD Odderon
The Hamiltonian derived by Bartels, Kwiecinski and Praszalowicz for the study
of high-energy QCD in the generalized logarithmic approximation was found to
correspond to the Hamiltonian of an integrable spin chain. We study the
odderon Hamiltonian corresponding to three sites by means of the Bethe Ansatz
approach. We rewrite the Baxter equation, and consequently the Bethe Ansatz
equations, as a linear triangular system. We derive a new expression for the
eigenvectors and the eigenvalues, and discuss the quantization of the conserved
quantities.Comment: 14 pages, latex file, one figur
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
Exact resolution of the Baxter equation for reggeized gluon interactions
The interaction of reggeized gluons in multi-colour QCD is considered in the
Baxter-Sklyanin representation, where the wave function is expressed as a
product of Baxter functions Q(lambda) and a pseudo-vacuum state. We find n
solutions of the Baxter equation for a composite state of n gluons with poles
of rank r in the upper lambda semi-plane and of rank n-1-r in the lower lambda
semi-plane (0 leq r leq n-1). These solutions are related by n-2 linear
equations with coefficients depending on coth (pi lambda). The poles cancel in
the wave function, bilinear combination of holomorphic and anti-holomorphic
Baxter functions, guaranteeing its normalizability. The quantization of the
intercepts of the corresponding Regge singularities appears as a result of the
physical requirements that the holomorphic energies for all solutions of the
Baxter equation are the same and the total energies, calculated around two
singularities lambda, lambda^* --> + i or -i, coincide. It results in simple
properties of the zeroes of the Baxter functions. For illustration we calculate
the parameters of the reggeon states constructed from three and four gluons.
For the Odderon the ground state has conformal spin |m -m | = 1 and its
intercept equals unity. The ground state of four reggeized gluons possesses
conformal spin 2 and its intercept turns out to be higher than that for the
BFKL Pomeron. We calculate the anomalous dimensions of the corresponding
operators for arbitrary alpha_s/omega.Comment: LaTex, 42 pages, 8 .ps figures. Expanded and improved versio
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
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
Integrable spin chains and scattering amplitudes
In this review we show that the multi-particle scattering amplitudes in N=4
SYM at large Nc and in the multi-Regge kinematics for some physical regions
have the high energy behavior appearing from the contribution of the Mandelstam
cuts in the complex angular momentum plane of the corresponding t-channel
partial waves. These Mandelstam cuts or Regge cuts are resulting from gluon
composite states in the adjoint representation of the gauge group SU(Nc). In
the leading logarithmic approximation (LLA) their contribution to the six point
amplitude is in full agreement with the known two-loop result.
The Hamiltonian for the Mandelstam states constructed from n gluons in LLA
coincides with the local Hamiltonian of an integrable open spin chain. We
construct the corresponding wave functions using the integrals of motion and
the Baxter-Sklyanin approach.Comment: Invited review for a special issue of Journal of Physics A devoted to
"Scattering Amplitudes in Gauge Theories", R. Roiban(ed), M. Spradlin(ed), A.
Volovich (ed
Production of electroweak gauge bosons in off-shell gluon-gluon fusion
We study the production of electroweak gauge bosons at high energies in the
framework of kt-factorization QCD approach. Contributions from the valence
quarks are calculated using the quark-gluon interaction and quark-antiquark
annihilation QCD subprocesses. The total and differential cross sections (as a
function of the transverse momentum and rapidity) are presented and the ratio
of cross sections for W and Z boson production is investigated. The
conservative error analysis is performed. In the numerical calculations two
different sets of unintegrated gluon distributions in the proton are used: the
one obtained from Ciafaloni-Catani-Fiorani-Marchesini evolution equation and
the other from Kimber-Martin-Ryskin prescription. Theoretical results are
compared with experimental data taken by the D0 and CDF collaborations at the
Tevatron. We demonstrate the importance of the quark component in parton
evolution in description of the experimental data. This component is very
significant also at the LHC energies.Comment: 33 pages, 18 figure
Diffractive photoproduction at large momentum transfer in coherent hadron - hadron interactions at CERN LHC
The vector meson production in coherent hadron-hadron interactions at LHC
energies is studied 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
rapidity distribution and total cross section for the process , where can be a proton or a nucleus. We predict large rates,
which implies that the experimental identification can be feasible at the LHC.Comment: 10 pages, 5 figures, 1 table. Version to be published in Physical
Review
BFKL at next-to-leading order
This is a summary of the contributions on the next-to-leading order
corrections to the BFKL equation which were presented to the `Small-x and
Diffraction' working group at the 1998 Durham Workshop on HERA Physics.Comment: 6 pages, 2 figure
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