arXiv subjects
Publications and source records attributed to J. Blümlein.
A brief overview is presented of recent developments concerning resummed small-x evolution, based upon the renormalization group equation. The non-singlet and singlet structure functions are discussed for both polarized and unpolarized deep-inelastic scattering. Quantitative results are displayed and uncertainties from uncalculated subleading terms are discussed.
The scalar and vector leptoquark pair production cross sections in hadronic collisions are calculated. In a model independent analysis we consider the most general C and P conserving couplings of gluons to both scalar and vector leptoquarks described by an effective low--energy Lagangian which obeys SU(3)_c invariance. Analytrical expressions are derived for the differential and integral scattering cross sections including the case of anomalous vector leptoquark couplings, $κ_G$ and $λ_G$, to the gluon field. Numerical predictions are given for the kinematic range of the TEVATRON and LHC. The pair production cross sections are also calculated for the resolved photon contributions to $ep \rightarrow e \overlineΦ ΦX$ at HERA and LEP $\otimes$ LHC, and for the process $γγ\rightarrow Φ\overline ΦX$ at possible future $e^+e^-$ linear colliders and $γγ$ colliders. Estimates of the search potential for scalar and vector leptoquarks at present and future high energy colliders are given.
The impact of the resummation of leading small-$x$ terms in the anomalous dimensions is briefly summarized for the evolution of non--singlet and singlet polarized structure functions.
An introduction and summary is given of the main results achieved by working group 1: Structure Functions in Deep Inelastic Scattering at HERA. The prospects were discussed of future measurements of the structure functions $F_{2}, F_{L}, xG_{3}, F_{2}^{Q\overline{Q}}$ and $F_π$ at HERA. The results represent a long term programme of experimentation with high luminosity, different lepton beam charges, proton and deuteron beams, allowing for precision measurements. The theoretical investigations focussed on QED corrections, higher order QCD corrections for different observables, resummation of small $x$ contributions, and the detailed understanding of NLO QCD evolution codes, to allow for a high precision analysis of the forthcoming deep inelastic data.
We perform a numerical study of the QCD corrections to the structure function $F_L(x,Q^2)$ in the HERA energy range. The $K$--factors are of $O(30%)$ and larger in parts of the kinematic range. The relative corrections to $F_L^{c\overline{c}}$ turn out to be scale dependent and partially compensate contributions to the massless terms.
We describe several numerical results for radiative corrections for deep inelastic $ep$ scattering at HERA which are calculated using the HECTOR package. We present radiative corrections for ten different choices of kinematical variables for unpolarized neutral and charged current deep inelastic scattering. Radiative corrections for neutral current scattering off polarized protons are calculated in leptonic variables and compared to those obtained by the POLRAD code for the kinematic regime of the HERMES experiment.
Seven next-to-leading order QCD evolution programs are compared. The deviations of the results due to different theoretical prescriptions for truncating the perturbative series are clarified, and a numerical agreement between five codes of better than 0.1% is achieved. Reference results for further comparison are provided.
The differences are discussed between various next-to-leading order prescriptions for the QCD evolution of parton densities and structure functions. Their quantitative impact is understood to an accuracy of 0.02\%. The uncertainties due to the freedom to choose the renormalization and factorization scales are studied. The quantitative consequences of the different uncertainties on the extraction of the strong coupling constant $α_s$ from scaling violations in deep--inelastic scattering are estimated for the kinematic regime accessible at HERA.
The scalar and vector leptoquark pair production cross sections for deep inelastic $ep$ scattering are calculated. Estimates are presented for the search potential at HERA.
A survey is given of recent developments on the resummed small-$x$ evolution, in a framework based on the renormalization group equation, of non--singlet and singlet structure functions in both unpolarized and polarized deep--inelastic scattering. The available resummed anomalous dimensions are discussed for all these cases, and the most important analytic and numerical results are compiled. The quantitative effects of these small-$x$ resummations on the evolution of the various parton densities and structure functions are presented, and their present uncertainties are investigated. An application to QED radiative corrections is given.
A brief survey is given of recent results on the resummation of leading small-x terms for unpolarized and polarized non--singlet and singlet structure function evolution.
The twist--2 contributions to the polarized structure functions in deep inelastic lepton--hadron scattering are calculated including the exchange of weak bosons and using both the operator product expansion and the covariant parton model. A new relation between two structure functions leading to a sequence of new sum rules is found. The light quark mass corrections to the structure functions are derived in lowest order QCD.
The resummation of $O(α_s^{l+1} \ln^{2l} x)$ terms in the evolution equation of the singlet part of $g_1(x,Q^2)$ is carried out. The corresponding singlet evolution kernels are calculated explicitely. The leading small-$x$ contribution to the three-loop splitting function matrix is determined in the $\overline{\rm MS}$ scheme. Relations are derived for the case of ${\cal N} = 1$ supersymmetric Yang--Mills field theory. Numerical results are presented for the polarized singlet and gluon densities, and the structure functions $g_1^{\, p}(x,Q^2)$ and $g_1^{\, n}(x,Q^2)$. They are compared for different assumptions on the non--perturbative input distributions, and the stability of the results against presently unknown subleading contributions is investigated.
The resummation of $O(α^{l+1} \ln^{2l} x)$ terms in the evolution kernels of non--singlet combinations of structure functions is investigated for both QED abd QCD. Numerical results are presented for unpolarized and polarized structure functions.
The twist-2 contributions to the polarized structure functions in deep inelastic lepton--hadron scattering are calculated including the exchange of weak bosons and using both the operator product expansion and the covariant parton model. A new relation between two structure functions leading to a sequence of new sum rules is found. The light quark mass corrections to the structure functions are derived in lowest order QCD.
The theoretical status of perturbative QED and QCD corrections to deep inelastic scattering is reviewed.
The $k_{\perp}$ dependent gluon distribution for protons, pions,and photons is calculated accounting for the resummation of small~$x$ effects due to the Lipatov equation. It is represented by a convolution of a gluon density in the collinear limit and a universal function ${\cal G}(x,k^2,μ)$ for which an analytic expression is derived.
The $k_{\perp}$ dependent gluon distribution is calculated accounting for the resummation of small~$x$ effects due to the Lipatov equation. It is represented by a convolution of a gluon density in the collinear limit and a universal function ${\cal G}(x,k^2,μ)$ for which an analytic expression is derived.