Searcharxiv⌕ Search

arXiv subjects

J. Blümlein

Publications and source records attributed to J. Blümlein.

At least 199 records · Page 11Linked to original sources
arXiv1998

Relations among polarized and unpolarized splitting functions beyond leading order

The role of various symmetries in the evaluation of splitting functions and coefficient functions is discussed. The scale invariance in hard processes is known to be a guiding tool to understand the dynamics. We discuss the constraints on splitting functions coming from various symmetries such as scale, conformal and supersymmetry. We also discuss the Drell-Levy-Yan relation among splitting and coefficient functions in various schemes. The relations coming from conformal symmetry are also presented.

hep-ph↗
arXiv1998

On the Gluon Regge Trajectory in $O(α_s^2)$

We recalculate the gluon Regge trajectory in next-to-leading order to clarify a discrepancy between two results in the literature on the constant part. We confirm the result obtained by Fadin et al.~\cite{FFK}. The effects on the anomalous dimension and on the $s^ω$ behavior of inclusive cross sections are also discussed.

hep-ph↗
arXiv1998

The Resummed Gluon Anomalous Dimension and Structure Functions at Small x

The impact of the resummed next-to-leading logarithmic small-$x$ contributions to the anomalous dimension $γ_{gg}$ is evaluated for the unpolarized parton densities and structure functions of the nucleon. These new terms diminish the gluon distribution and overcompensate the contribution caused by the resummed leading logarithmic small-$x$ anomalous dimension and the quarkonic anomalous dimensions beyond next-to-leading order.

hep-ph↗
arXiv1998

The Evolution of Unpolarized Singlet Structure Functions at Small x

A systematic study is performed of the impact of the various resummed small-$x$ contributions to the anomalous dimensions and coefficient functions on the evolution of unpolarized structure functions in deep-inelastic scattering. The proton structure functions $F_2^p$ and $F_L^p$ as well as the photon structure function $F_2^γ$ are considered together with the corresponding parton densities. The general analytic solution of the evolution equations in Mellin-$N$ space is derived, and different approximate solutions are compared. Potential effects of less singular small-$x$ terms in the anomalous dimension and coefficient functions are discussed.

hep-ph↗
arXiv1997

Twist-2 Light-Ray Operators: Anomalous Dimensions and Evolution Equations

The non-singlet and singlet anomalous dimensions of the twist--2 light-ray operators for unpolarized and polarized deep inelastic scattering are calculated in $O(α_s)$. We apply these results for the derivation of evolution equations for partition functions, structure functions, and wave functions which are defined as Fourier transforms of the matrix elements of the light-ray operators. Special cases are the Altarelli-Parisi and Brodsky-Lepage kernels. Finally we extend Radyushkin's solution from the non-singlet to the singlet case.

hep-ph↗
arXiv1997

O(α) QED Corrections to Polarized Elastic $μe$ and Deep Inelastic l N Scattering

Two computer codes relevant for the description of deep inelastic scattering off polarized targets are discussed. The code $μ$ela deals with radiative corrections to elastic $μe$ scattering, one method applied for muon beam polarimetry. The code HECTOR allows to calculate both the radiative corrections for unpolarized and polarized deep inelastic scattering, including higher order QED corrections.

hep-ph↗
arXiv1997

Summary of Working Group I: Hadron Structure

A summary is given on the main aspects which were discussed by the working group. They include new results on the deep inelastic scattering structure functions $F_2, xF_3, F_L$ and $F_2^{c\bar{c}}$ and their parametrizations, the measurement of the gluon density, recent theoretical work on the small $x$ behavior of structure functions, theoretical and experimental results on $α_s$, the direct photon cross section, and a discussion of the event rates in the high $p_T$ range at Tevatron and the high $Q^2$ range at HERA, as well as possible interpretations.

hep-ph↗
arXiv1997

Small-x Resummation for the Structure Functions $F_2^p$, $F_L^p$ and $F_2^γ$

The numerical effects of the known all-order leading and next-to-leading logarithmic small-$x$ contributions to the anomalous dimensions and coefficient functions of the unpolarized singlet evolution are discussed for the structure functions $F_2^{ ep}(x,Q^2)$, $F_L^{ ep}(x,Q^2)$, and $F_2^{ eγ}(x,Q^2)$.

hep-ph↗
arXiv1997

Evolution Kernels for Light-Ray Operators: Twist 2 and Twist 3 Contributions

The general evolution kernels of the twist 2 light-ray operators for unpolarized and polarized deep inelastic scattering are calculated in ${\cal O}(α_s)$. From these evolution kernels a series of special evolution equations can be derived, among them the Altarelli-Parisi equations and the evolution equation for the meson wave function. In the case of twist 3 the results of Balitzki and Braun are confirmed.

hep-ph↗
arXiv1997

On the Evolution Kernels of Twist 2 Light-Ray Operators for Unpolarized and Polarized Deep Inelastic Scattering

The non-singlet and singlet evolution kernels of the twist--2 light-ray operators for unpolarized and polarized deep inelastic scattering are calculated in $O(α_s)$ for the general case of virtualities $q^2, q'^2 \neq 0$. Special cases as the kernels for the general single-variable evolution equation and the Altarelli-Parisi and Brodsky-Lepage limits are derived from these results.

hep-ph↗
arXiv1997

On the Expectations for Leptoquarks in the Mass Range of O(200 GeV)

A summary is given on the experimental bounds for the couplings and masses of scalar and vector leptoquarks associated to the first fermion generation. We investigate to which extent an interpretation of the recently reported excess of events in the large $x$ and $Q^2$ range at HERA in terms of single leptoquark production is compatible with other experimental results.

hep-ph↗
arXiv1996

$O(α)$ QED Corrections to Neutral Current Polarized Deep-Inelastic Lepton-Nucleon Scattering

The $O(α)$ leptonic QED corrections to neutral current polarized deep inelastic lepton-nucleon scattering are calculated in leptonic variables both for the case of longitudinal and transverse nucleon polarization. The results of the complete calculation are compared with the corresponding leading log expressions. Numerical results are presented for the corrections in the kinematic range of the HERMES experiment and possible future polarized proton beam experiments at HERA.

hep-ph↗
arXiv1996

On the Twist 2 and Twist 3 Contributions to the Spin-dependent Electroweak Structure Functions

The twist 2 and twist 3 contributions of the polarized deep-inelastic structure functions are calculated both for neutral and charged current interactions using the operator product expansion in lowest order in QCD. The relations between the different structure functions are determined. New integral relations are derived between the twist 2 contributions of the structure functions $g_3(x,Q^2)$ and $g_5(x,Q^2)$ and between combinations of the twist 3 contributions to the structure functions $g_2(x,Q^2)$ and $g_3(x,Q^2)$. The sum rules for polarized deep inelastic scattering are discussed in detail.

hep-ph↗
arXiv1996

Vector Leptoquark Pair Production in $e^+e^-$ Annihilation

The cross section for vector leptoquark pair production in $e^+e^-$ annihilation is calculated for the case of finite anomalous gauge boson couplings $κ_{γ, Z}$ and $λ_{γ, Z}$. The minimal cross section is found to behave $\propto β^7$, leading to weaker mass bounds in the threshold range than in models studied previously.

hep-ph↗