15,643 research outputs found
Nonlinearity of vacuum reggeons and exclusive diffractive production of vector mesons at HERA
The processes of exclusive photo- and electroproduction of vector mesons
(770), (1020) and (3096) at collision energies and transferred momenta squared are considered in
the framework of a phenomenological Regge-eikonal scheme with nonlinear Regge
trajectories in which their QCD asymptotic behavior is taken into account
explicitly. By comparison of available experimental data from ZEUS and H1
Collaborations with the model predictions it is demonstrated that corresponding
angular distributions and integrated cross-sections in the above-mentioned
kinematical range can be quantitatively described with use of two -even
vacuum Regge trajectories. These are the "soft" pomeron dominating the high
energy reactions without a hard scale and the "hard" pomeron giving an
essential contribution to photo- and electroproduction of heavy vector mesons
and deeply virtual electroproduction of light vector mesons.Comment: 25 pages, 12 figure
Dynamically Generated Open and Hidden Charm Meson Systems
We will study open and hidden charm scalar meson resonances within two
different models. The first one is a direct application of a chiral Lagrangian
already used to study flavor symmetry breaking in Skyrme models. In another
approach to the problem a SU(4) symmetric Lagrangian is built and the symmetry
is broken down to SU(3) by identifying currents where heavy mesons are
exchanged and suppressing those. Unitarization in couple channels leads to
dynamical generation of resonances in both models, in particular a new hidden
charm resonance with mass 3.7 GeV is predicted. The small differences between
these models and with previous works will be discussed.Comment: 32 pages, 10 figures. Added extra calculations with explicit symmetry
breaking terms in chiral Lagrangian
Elliptic fibrations associated with the Einstein spacetimes
Given a conformally nonflat Einstein spacetime we define a fibration over
it. The fibres of this fibration are elliptic curves (2-dimensional tori) or
their degenerate counterparts. Their topology depends on the algebraic type of
the Weyl tensor of the Einstein metric. The fibration is a double branched
cover of the bundle of null direction over the spacetime and is equipped with
six linearly independent 1-forms which satisfy certain relatively simple system
of equations.Comment: 15 pages, Late
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