The Polarized Two-loop Splitting Functions
We present a brief description of the light-cone gauge calculation of the spin-dependent next-to-leading order splitting functions.
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arXiv subjects
W. Vogelsang
Publications and source records attributed to W. Vogelsang.
Isolated Prompt Photon Production at HERA
We study the expectations for prompt photon production rates at HERA in a fully consistent next-to-leading order (NLO) QCD analysis, taking into account the effects of experimental isolation requirements. In particular we examine the sensitivity of the isolated cross section to the photon's gluon content.
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Spin - Dependent Parton Distributions of the Longitudinally Polarized Photon Beyond the Leading Order
A next-to-leading order (NLO) QCD analysis of the spin-dependent parton distributions $Δf^γ(x,Q^2)$ of the longitudinally polarized photon and of its structure function $g_1^γ(x,Q^2)$ is performed within the framework of the radiative parton model. The important issues of a suitably chosen factorization scheme and related boundary conditions are discussed in detail. The typical effects of the NLO corrections are quantitatively studied for two very different conceivable scenarios for the NLO polarized parton distributions $Δf^γ(x,Q^2)$.
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Photoproduction of Jets and Heavy Flavors at Future Polarized ep - Colliders
We study photoproduction of jets and heavy flavors in a polarized collider mode of HERA and in polarized $ep$ collisions at $\sqrt{S}\approx 30$ GeV. We examine the sensitivity of the cross sections and their asymmetries to the proton's polarized gluon distribution and to the completely unknown parton distributions of longitudinally polarized photons.
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The spin-dependent two-loop splitting functions
We present a complete description of the calculation of the spin-dependent next-to-leading order splitting functions. The calculation is performed in the light-cone gauge. We give results for different prescriptions for the Dirac matrix $γ_5$ in $d=4-2 ε$ dimensions and provide the link to the results in dimensional reduction.
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The evolution of parton distributions beyond leading order: the singlet case
A complete description of the calculation of anomalous dimensions (GLAP splitting functions) is given for parton distributions which appear in space-like processes. The calculation is performed in the light-cone gauge. The results are in agreement with the previous results of Furmanski and Petronzio.
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Next-to-Leading Order Radiative Parton Model Analysis of Polarized Deep Inelastic Scattering
A next-to-leading order QCD analysis of spin asymmetries and structure functions in polarized deep inelastic lepton nucleon scattering is presented within the framework of the radiative parton model. A consistent NLO formulation of the $Q^2$-evolution of polarized parton distributions yields two sets of plausible NLO spin dependent parton distributions in the conventional $\overline{\rm{MS}}$ factorization scheme. They respect the fundamental positivity constraints down to the low resolution scale $Q^2=μ^2_{NLO}=0.34\,{\rm{GeV}}^2$. The $Q^2$-dependence of the spin asymmetries $A_1^{p,n,d}(x,Q^2)$ is similar to the leading-order (LO) one in the range $1\le Q^2\le 20\,{\rm{GeV}}^2$ and is shown to be non-negligible for $x$-values relevant for the analysis of the present data and possibly forthcoming data at HERA.
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A Rederivation of the Spin-dependent Next-to-leading Order Splitting Functions
We perform a new calculation of the polarized next-to-leading order splitting functions, using the method developed by Curci, Furmanski and Petronzio. We confirm the results of the recent calculation by Mertig and van Neerven.
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Radiatively Generated Parton Distributions of Polarized Hadrons and Photons
A next-to-leading order QCD analysis of spin asymmetries and structure functions in polarized deep inelastic lepton nucleon scattering is presented within the framework of the radiative parton model. The $Q^2$-dependence of the spin asymmetry $A_1^{p}(x,Q^2)$ is shown to be non-negligible for $x$-values relevant for the analysis of the present data. In the second part of the paper we present LO results for radiatively generated spin-dependent parton distributions of the photon and for its structure function $g_1^γ$.
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Spin-dependent non-singlet structure functions in next-to-leading order
We study in detail the flavor-non-singlet component of polarized structure functions in the framework of a consistent and complete next-to-leading order (${\cal O}(α_s))$ analysis. In this context, we discuss some important features of the calculation of the next-to-leading order corrections. Particular emphasis is put on the $Q^2$-evolution of sum-rules for the first moments of the non-singlet structure functions which, as we show, could serve to explore $SU(2)$ and $SU(3)$ breaking effects in relations between baryonic $β$-decay matrix elements and in the proton's polarized sea. Furthermore we make predictions for polarized non-singlet structure functions measurable in a conceivable $\vec{e}\vec{p}$ collider mode of HERA.
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Radiative Parton Model Analysis of Polarized Deep Inelastic Lepton Nucleon Scattering
A leading order QCD analysis of spin asymmetries in polarized deep inelastic lepton nucleon scattering is presented within the framework of the radiative parton model. Two resulting sets of plausible leading order spin dependent parton distributions are presented, respecting the fundamental positivity constraints down to the low resolution scale $Q^2=μ_{LO}^2=0.23$ GeV$^2$. The $Q^2$ dependence of the spin asymmetries $A_1^{p,n,d}(x,Q^2)$ is investigated in the range $1 \leq Q^2 \leq 20$ GeV$^2$ and shown to be non-negligible for $x$-values relevant for the analysis of present data and possibly forthcoming data at HERA.
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Constraints on the Proton's Gluon Distribution from Prompt Photon Production
We analyze the capability of prompt photon production in pp and pp(bar) collisions to constrain the gluon distribution of the proton, considering data from fixed-target experiments as well as collider measurements. Combined fits are performed to these large-p_T direct gamma cross sections and lepton-proton deep-inelastic scattering data in the framework of next-to-leading order perturbative QCD. Special attention is paid to theoretical uncertainties originating from the scale dependence of the results and from the fragmentation contribution to the prompt photon cross section.
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