236 research outputs found
Hard Pomeron in exclusive meson production at ILC
We calculate the exclusive process gamma* gamma* ->rho rho at high energy.
The Born order estimate and the leading (LLA) and next to leading order (NLLA)
BFKL resummation effects show the feasibility of experimental detection in a
quite large range of Q2 values at future high energy e+e- linear colliders.Comment: 4 pages, Presented at Photon2005, International Conference on the
Structure and Interactions of the Photon, Warsaw 31.08-04.09.2005, by Samuel
Wallo
Probing Transversity GPDs in Photo and Electroproduction of Two Vector Mesons
Electroproduction of two mesons well separated in rapidity allows the first
feasible selective access to chiral-odd transversity GPDs provided one of these
mesons is a transversely polarized vector meson rho_T.Comment: 3 pages, 5 figures, to be published in the proceedings of the
International Conference on the Structure and Interactions of the Photon
(Photon 2007) Paris, july 200
Testing the dynamics of high energy scattering using vector meson production
I review work on diffractive vector meson production in photon-proton
collisions at high energy and large momentum transfer, accompanied by proton
dissociation and a large rapidity gap. This process provides a test of the high
energy scattering dynamics, but is also sensitive to the details of the
treatment of the vector meson vertex.
The emphasis is on the description of the process by a solution of the
non-forward BFKL equation, i.e. the equation describing the evolution of
scattering amplitudes in the high-energy limit of QCD. The formation of the
vector meson and the non-perturbative modeling needed is also briefly
discussed.Comment: 17 pages, 8 figures. Brief review to appear in Mod. Phys. Lett.
Transversity GPD in photo- and electroproduction of two vector mesons
The chiral-odd generalized parton distribution (GPD), or transversity GPD, of
the nucleon can be accessed experimentally through the photo- or
electroproduction of two vector mesons on a polarized nucleon target,
\gamma^(*) N --> \rho_1 \rho_2 N', where \rho_1 is produced at large transverse
momentum, \rho_2 is transversely polarized, and the mesons are separated by a
large rapidity gap. We predict the cross section for this process for both
transverse and longitudinal \rho_{2} production. To this end we propose a model
for the transversity GPD H_T(x,\xi,t), and give an estimate of the relative
sizes of the transverse and longitudinal \rho_{2} cross sections. We show that
a dedicated experiment at high energy should be able to measure the
transversity content of the proton.Comment: 15 pages, 9 figures. Extended discussion of experimental prospects in
the conclusions. Version to appear in EPJ
Hard exclusive reactions and hadron structure
The generalized Bjorken regime of exclusive reactions opens new ways to
explore the hadron structure. We shortly review the present status of this
domain where generalized parton distributions, generalized distribution
amplitudes and transition distribution amplitudes describe various aspects of
confinement physics.Comment: 7 pages LATEX, 5 figures, invited talk at the Vth Conference on
Hadronic Physics held at ICTP, Trieste, Italy, May 200
Vector Meson Photoproduction from the BFKL Equation II: Phenomenology
Diffractive vector meson photoproduction accompanied by proton dissociation
is studied for large momentum transfer. The process is described by the
non-forward BFKL equation which we use to compare to data collected at the HERA
collider.Comment: 39 pages, 29 figure
DGLAP versus perturbative Pomeron in large momentum transfer hard diffractive processes at HERA and LHC
We evaluate within the LO DGLAP approximation the dependence on energy of the
cross section of the photo(electro)production of vector meson V
() in the hard elastic processes off a parton as the function of momentum transfer . We
demonstrate that in the limit the cross section does not
contain double logarithmic terms in any order of the DGLAP approximation
leading to the energy independent cross section. Thus the energy dependence of
cross section is governed at
large by the gluon distribution within a proton, i.e. it is unambiguously
predicted within the DGLAP approximation including the stronger
dependence at larger . This prediction explains recent HERA data. The
calculations which follow perturbative Pomeron logic predict opposite trend of
a weaker dependence at larger . We explain that at the HERA
energies double logarithmic terms characteristic for DGLAP approximation
dominate in the hard processes as the consequence of constraints due to
energy-momentum conservation. We give predictions for ultraperipheral hard
diffractive processes at the LHC and show that these processes are well suited
for looking for the contribution of the single logarithmic terms due to the
gluon emission in the multiRegge kinematics. We also comment on the
interrelation between energy and dependence of the cross sections of the
hard exclusive processes.Comment: 12 pages, 3 figure
Gaps between Jets in the High Energy Limit
We use perturbative QCD to calculate the parton level cross section for the
production of two jets that are far apart in rapidity, subject to a limitation
on the total transverse momentum Q0 in the interjet region. We specifically
address the question of how to combine the approach which sums all leading
logarithms in Q/Q0 (where Q is the jet transverse momentum) with the BFKL
approach, in which leading logarithms of the scattering energy are summed. This
paper constitutes progress towards the simultaneous summation of all important
logarithms. Using an "all orders" matching, we are able to obtain results for
the cross section which correctly reproduce the two approaches in the
appropriate limits.Comment: 29 pages, 9 figures, minor corrections to text and improved figure
Rapidity gaps at HERA and the Tevatron from soft colour exchanges
Models based on soft colour exchanges to rearrange colour strings in the
final state provide a general framework for both diffractive and
non-diffractive events in ep and hadron-hadron collisions. We study two such
models and find that they can reproduce rapidity gap data from both HERA and
the Tevatron. We also discuss the influence of parton cascades and multiple
interactions on the results.Comment: 4 pages, 4 EPS figures, presented at UK Phenomenology Workshop on
Collider Physics, Durham. Uses iopart.cl
QCD factorizations in gamma* gamma* -> rho rho
We calculate the lowest order QCD amplitude, i.e. the quark exchange
contribution, to the forward production amplitude of a pair of longitudinally
polarized mesons in the scattering of two virtual photons . We show that the scattering amplitude
simultaneously factorizes in two quite different ways: the part with transverse
photons is described by the QCD factorization formula involving the generalized
distribution amplitude of two final mesons, whereas the part with
longitudinally polarized photons takes the QCD factorized form with the
transition distribution amplitude. Perturbative
expressions for these, in general, non-perturbative functions are obtained in
terms of the meson distribution amplitude
- âŠ