6,624 research outputs found
Double-logarithms in Einstein-Hilbert gravity and supergravity
We study the interplay between graviton reggeization and double-logarithmic
in energy contributions to four-graviton scattering in theories with and
without supersymmetry. Predictions to all orders in the gravitational coupling
are given for these double-logarithms. As the number of supersymmetries grows
these terms generate a convergent behaviour for the amplitudes at very high
energies. At two-loop level, we find agreement with previous exact results for
N=8 supergravity and with those of Boucher-Veronneau and Dixon, who studied the
N=4,5,6 supergravities using a conjectured double-copy structure of gravity
Saturation Effects in Deep Inelastic Scattering at low and its Implications on Diffraction
We present a model based on the concept of saturation for small and
small . With only three parameters we achieve a good description of all Deep
Inelastic Scattering data below . This includes a consistent treatment
of charm and a successful extrapolation into the photoproduction regime. The
same model leads to a roughly constant ratio of diffractive and inclusive cross
section.Comment: 24 pages, 12 figures, Latex-fil
Off-Shell Scattering Amplitudes for WW Scattering and the Role of the Photon Pole
We derive analytic expressions for high energy off-shell scattering
amplitudes of weak vector bosons. They are obtained from six fermion final
states in processes of the type . As an application we reconsider the
unitarity bounds on the Higgs mass. Particular attention is given to the role
of the photon exchange which has not been considered in earlier investigations;
we find that the photon weakens the bound of the Higgs mass.Comment: 16 pages, 8 figure
NLO Corrections to the kernel of the BKP-equations
We present results for the NLO kernel of the BKP equations for composite
states of three reggeized gluons in the Odderon channel, both in QCD and in N=4
SYM. The NLO kernel consists of the NLO BFKL kernel in the color octet
representation and the connected kernel, computed in the tree
approximation.Comment: 28 pages, 7 figure
Geometric Scaling in Inclusive Charm Production
We show that the cross section for inclusive charm production exhibits
geometric scaling in a large range of photon virtualities. In the HERA
kinematic domain the saturation momentum stays below the hard
scale , implying charm production probing mostly the color
transparency regime and unitarization effects being almost negligible. We
derive our results considering two saturation models which are able to describe
the DESY ep collider HERA data for the proton structure function at small
values of the Bjorken variable . A striking feature is the scaling on
above saturation limit, corroborating recent
theoretical studies.Comment: 4 pages, 2 figures. Version to be published in Physical Review
Letter
Helicity Parton Distributions at a Future Electron-Ion Collider: A Quantitative Appraisal
We present a quantitative assessment of the impact a future electron-ion
collider will have on determinations of helicity quark and gluon densities and
their contributions to the proton spin. Our results are obtained by performing
a series of global QCD analyses at next-to-leading order accuracy based on
realistic sets of pseudo-data for the inclusive and semi-inclusive
deep-inelastic scattering of longitudinally polarized electrons and protons at
different, conceivable center-of-mass system energies.Comment: 11 pages, 8 figure
Saturation and geometric scaling in DIS at small x
We present various aspects of the saturation model which provides good
description of inclusive and diffractive DIS at small x. The model uses parton
saturation ideas to take into account unitarity requirements. A new scaling
predicted by the model in the small x domain is successfully confronted with
the data.Comment: Presented at New Trends in HERA Physics 2001, Ringberg Castle,
Tegernsee, Germany, 17-22 June 2001, minor corrections, some references adde
Effective action for the Regge processes in gravity
It is shown, that the effective action for the reggeized graviton
interactions can be formulated in terms of the reggeon fields and
and the metric tensor in such a way, that it is local in
the rapidity space and has the property of general covariance. The
corresponding effective currents and satisfy the
Hamilton-Jacobi equation for a massless particle moving in the gravitational
field. These currents are calculated explicitly for the shock wave-like fields
and a variation principle for them is formulated. As an application, we
reproduce the effective lagrangian for the multi-regge processes in gravity
together with the graviton Regge trajectory in the leading logarithmic
approximation with taking into account supersymmetric contributions.Comment: 39 page
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