6 research outputs found
Near-integrability and confinement for high-energy hadron-hadron collisions
We investigate an effective Hamiltonian for QCD at large s, in which
longitudinal gauge degrees of freedom are suppressed, but not eliminated. In an
axial gauge the effective field theory is a set of coupled (1+1)-dimensional
principal-chiral models, which are completely integrable. The confinement
problem is solvable in this context, and we find the longitudinal and
transverse string tensions with techniques already used for a similar
Hamiltonian in (2+1)-dimensions. We find some a posteriori justification for
the effective Hamiltonian as an eikonal approximation. Hadrons in this
approximation consist of partons, which are quarks and soliton-like excitations
of the sigma models. Diffractive hadron-hadron scattering appears primarily due
to exchange of longitudinal flux between partons.Comment: Typographical errors corrected, language improved, reference adde
High energy scattering in 2+1 QCD
High energy scattering in 2+1 QCD is studied using the recent approach of
Verlinde and Verlinde. We calculate the color singlet part of the quark-quark
scattering exactly within this approach, and discuss some physical implication
of this result. We also demonstrate, by two independent methods, that
reggeization fails for the color singlet channel. We briefly comment on the
problem in 3+1 QCD.Comment: 20 pages, references adde
The dependence of the hard diffractive photoproduction of vector meson or photon and the range of pQCD validity
We consider two coupled problems.
We study the dependence on photon virtuality for the semihard
quasi--elastic photoproduction of neutral vector mesons on a quark, gluon or
real photon (at
GeV)). To this end we calculate the corresponding amplitudes (in an
analytical form) in the lowest nontrivial approximation of perturbative QCD. It
is shown that the amplitude for the production of light meson varies very
rapidly with the photon virtuality near .
We estimate the bound of the pQCD validity region for such processes. For the
real incident photon the obtained bound for the meson production is very
high. This bound decreases fast with the increase of , and we expect that
the virtual photoproduction at HERA gives opportunity to test the pQCD results.
The signature of this region is discussed. For the hard Compton effect the pQCD
should work good at not too high , and this effect seems measurable
at HERA.Comment: ReVTeX, 36 pages, 5 Postscript figures, uses epsf.st
Infrared safety of impact factors for colourless particle interactions
We demonstrate, to next-to-leading order accuracy, the cancellation of the
infrared singularities in the impact factors which arise in the QCD description
of high energy processes A + B -> A' + B' of colourless particles. We study the
example where A is a virtual photon in detail, but show that the result is true
in general.Comment: 31 pages latex including 10 figure