364 research outputs found
The photon structure and exclusive production of vector mesons in gamma-gamma collisions
The process of exclusive vector meson production (gamma gamma to J/psi rho^0)
is studied for almost real photons. This process may be reduced to
photoproduction of J/psi off the rho^0 meson. We discuss the possibility of
extracting the gluon distribution of rho^0 and of the photon from such
measurement. Predictions are also given for the reaction (e+e- to e+ e- J/psi
rho^0) for various e+e- cms energies typical for LEP and for the future linear
colliders.Comment: 10 pages with 3 Postscript figure
Evidence for breakdown of the DGLAP description in diffractive DIS at HERA
HERA data on diffractive DIS show deviations from twist 2 DGLAP predictions
below GeV at low pomeron , which may reach up to 100%.
These deviations are consistent with higher twists effects extracted from the
saturation model. It is a first direct evidence for the higher twists in DIS.
This finding affects determination of the diffractive parton densities that are
used for the predictions at the LHC.Comment: 5 pages, 2 figures, Based on the talk presented at the conference
Deep-Inelastic Scattering and Related Subjects (DIS2012), Bonn, 201
Evidence of strong higher twist effects in diffractive DIS at HERA at moderate Q2
We study a twist decomposition of diffractive structure functions in the
diffractive deep inelastic scattering (DDIS) at HERA. At low Q2 and at large
energy the data exhibit a strong excess, up to about 100%, above the twist 2
NLO DGLAP description. The excess in consistent with higher twist effects. It
is found, that complementing the DGLAP fit by twist 4 and 6 components of the
GBW saturation model leads to a good description of data at low Q2. We conclude
that the DDIS at HERA provides the first, strong evidence of higher twist
effects in DIS.Comment: 4 pages, 2 PDF figure
- …