387 research outputs found
Status of Polarized and Unpolarized Deep Inelastic Scattering
The current status of deep inelastic scattering is briefly reviewed. We
discuss future theoretical developments desired and measurements needed to
further complete our understanding of the picture of nucleons at short
distances.Comment: 9 pages, 2 figure
Precision of electro--weak couplings of scalar leptoquarks at TESLA
We investigate the potential to measure the electro-weak couplings of scalar
leptoquarks at TESLA for energies in the range of \sqrt{s} \simeq 1
\TeV using the pair production process .Comment: 4 pages LATEX, 2 Refs. adde
A Kinematic Condition on Intrinsic Charm
We derive a kinematic condition on the resolution of intrinsic charm and
discuss phenomenological consequences.Comment: 6 pages, 3 Figures, final version appearing in the Journa
Reduction of Multiple Harmonic Sums and Harmonic Polylogarithms
The alternating and non-alternating harmonic sums and other algebraic objects
of the same equivalence class are connected by algebraic relations which are
induced by the product of these quantities and which depend on their index
calss rather than on their value. We show how to find a basis of the associated
algebra. The length of the basis is found to be , where is
the depth of the sums considered and is given by the 2nd {\sc Witt} formula. It
can be also determined counting the {\sc Lyndon} words of the respective index
set. The relations derived can be used to simplify results of higher order
calculations in QED and QCD.Comment: 4 pages, 1 style file, to appear in the Proceedings of ACAT03,
Tsukuba, Japan Refereces update
Representation of the virtual Compton amplitude for polarized scattering in the generalized Bjorken region
The Compton amplitude is calculated in terms of expectation values of
light-ray quark operators. As a technical tool we apply the nonlocal light-cone
expansion. Thereby we express the expectation value of the vector light-ray
operator with the help of the expectation value of the corresponding scalar
operator of twist 2. This allows important simplifications. In the limit of
forward scattering the integral relations between the twist-2 contributions of
the structure functions are implied directly.Comment: 3 pages LATEX, 1 style file. Contribution to the Proceedings of the
7th International Workshop on Deep Inelastic Scattering and QCD, Zeuthen,
April 1999, Nucl. Phys. B (Proc. Suppl.
Leptoquark Pair Production in \gamma\gamma Scattering: Threshold Resummation
The possibilities to pair-produce leptoquarks in photon-photon collisions are
discussed. QCD threshold corrections lead to a strong enhancement of the
production cross section. Suitably long-lived leptoquarks (\Gamma_\Phi \lsim
100 \MeV) may form Leptoquarkonium states.Comment: 7 pages LATEX, 2 eps figures. Contribution to the Proceedings of the
\gamma \gamma Workshop, 200
Computer algebra tools for Feynman integrals and related multi-sums
In perturbative calculations, e.g., in the setting of Quantum Chromodynamics
(QCD) one aims at the evaluation of Feynman integrals. Here one is often faced
with the problem to simplify multiple nested integrals or sums to expressions
in terms of indefinite nested integrals or sums. Furthermore, one seeks for
solutions of coupled systems of linear differential equations, that can be
represented in terms of indefinite nested sums (or integrals). In this article
we elaborate the main tools and the corresponding packages, that we have
developed and intensively used within the last 10 years in the course of our
QCD-calculations
Universal Higher Order QED Corrections to Polarized Lepton Scattering
We calculate the universal radiative QED corrections to polarized lepton
scattering for general scattering cross sections in analytic form. The flavor
non--singlet and singlet radiation functions are calculated to . The resummation of the non--singlet and singlet contributions to the
QED--anomalous dimensions is performed to all
orders. Numerical results are presented for the individual radiation functions.
Applications to polarized deeply inelastic lepton--nucleon scattering are
given.Comment: 39 pages, latex, 1syle file, 11 figure
On the Structure of the Virtual Compton Amplitude in the Generalized Bjorken Region: Integral Relations
A systematic study is performed of the structure of the twist-2 contributions
to the virtual Compton amplitude in deep-inelastic non-forward scattering for
general spin states in the non-local light cone expansion. The gauge invariance
is proven in this approach for the twist-2 contributions for non-forward
scattering. Relations are derived between the contributing non-forward
amplitudes.Comment: 23 pages LATEX, 1 style file, slightly extended versio
On the Behaviour of Non--Singlet Structure Functions at Small
The resummation of terms in the evolution
kernels of non--singlet combinations of unpolarized and polarized structure
functions is investigated. The agreement with complete calculations up to order
is demonstrated, and the leading small- contributions to the
three--loop non--singlet splitting functions are derived. The
additional contributions due to the resummed terms are studied numerically for
the most important non--singlet structure functions. They are found to be about
or smaller in the kinematical regions accessible at present and in the
foreseeable future.Comment: 10 pages, encoded ps file using uufile
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