Visualization of task execution in ABB 800xA

The 1131-tasks that execute within the 800xA controller have been visualized by implementing three components extending the functionality of the 800xA control and automation platform. The components named TaskVisualizerCommServer (TSCS) and TaskVisualizerCommClient (TSCC) have been added to the controller and control builder respectively and are responsible for data collection and networking. The third component named Visualizer is a stand alone component handling graphical presentation and associated data handlin

A QCD analysis of HERA and fixed target structure function data

The parton momentum densities in the proton are obtained from a NLO QCD analysis of structure functions measured by HERA and fixed target experiments. The uncertainties in these parton densities, the structure functions and related cross sections are estimated from the experimental errors, taking into account all correlations. Standard Model predictions for the charged current Born cross sections at large x and Q2 are calculated and compared with recent data from ZEUS.Comment: 4 pages LaTeX, 5 eps figures, uses npb.sty. Presented at DIS99, Zeuthen, Germany, April 19-23, 199

Evolution of Parton Distributions

I present a highly efficient method for evolving parton distributions in perturbative QCD. The method allows evolving the parton distribution functions according to any of the commonly-used truncations of the evolution equations (which differ in their treatment of higher-order terms). I also give formul\ae\ for computing crossing functions within the method.Comment: 28 pages, TeX, "draft" notice delete

Structure function evolution at next-to-leading order and beyond

Results are presented of two studies addressing the scaling violations of deep-inelastic structure functions. Factorization-scheme independent fits to all ep and mu p data on F_2 are performed at next-to-leading order (NLO), yielding alpha_s(M_Z) = 0.114 +- 0.002_exp (+0.006-0.004)_th . In order to reduce the theoretical error dominated by the renormalization-scale dependence, the next-higher order (NNLO) needs to be included. For the flavour non-singlet sector, it is shown that available calculations provide sufficient information for this purpose at x > 10^-2.Comment: 3 pages LaTeX including 4 eps-figures, uses npb.sty. Talk presented at DIS'99, DESY-Zeuthen, April 1999. To appear in the proceeding

Solving the Altarelli-Parisi equations with truncated moments

The technique of truncated moments of parton distributions allows us to study scaling violations without making any assumption on the shape of parton distributions. The numerical implementation of the method is however difficult, since the evolution equations for truncated moments are not diagonal. We present a simple way to improve the efficiency of the numerical solution of the evolution equations for truncated moments. As a result, the number of truncated moments needed to achieve the required precision in the evolution is significantly smaller than in the original formulation of the technique. The method presented here can also be used to obtain the value of parton distributions in terms of truncated moments, and therefore it can be viewed as a technique for the solution of the Altarelli-Parisi equations.Comment: 10 pages Late

Impact of the three-loop corrections on the QCD analysis of the deep-inelastic-scattering data

We perform the analysis of the existing inclusive deep inelastic scattering (DIS) data within NNLO QCD approximation. The parton distributions functions (PDFs) and the value of strong coupling constant $\alpha_{s}(M_Z)=0.1143\pm0.0013 (exp)$ are obtained. The sensitivity of the PDFs to the uncertainty in the value of the NNLO corrections to the splitting functions is analyzed. It is shown that the PDFs errors due to this uncertainty is generally less than the experimental uncertainty in PDFs through the region of $x$ spanned by the existing DIS data.Comment: 9 pages, LATEX, 4 figures (EPS). After fixing bug, which caused incomplete account of the NNLO corrections in the fitting program, the fitted value of \alpha_s(M_Z)(NNLO) decreased by 0.002. The PDFs values changed within their experimental errors, the conclusions remain unchange

The Evolution of Unpolarized and Polarized Structure Functions at Small xx

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.Comment: 18 pages Latex, including 11 eps-figures, and a style file. To appear in: Proc. of the International Workshop: QCD and QED in Higher Orders, Rheinsberg, April, 1996, Nucl. Phys. B (Proc. Suppl

NLO prescription for unintegrated parton distributions

We show how parton distributions unintegrated over the parton transverse momentum, k_t, may be generated, at NLO accuracy, from the known integrated (DGLAP-evolved) parton densities determined from global data analyses. A few numerical examples are given, which demonstrate that sufficient accuracy is obtained by keeping only the LO splitting functions together with the NLO integrated parton densities. However, it is important to keep the precise kinematics of the process, by taking the scale to be the virtuality rather than the transverse momentum, in order to be consistent with the calculation of the NLO splitting functions.Comment: 20 pages, 8 figures. v2: version to appear in Eur. Phys. J.

Determination of alpha_s from F_2^p at HERA

We compute the proton structure function F_2^p at small x and large Q^2 at next-to-leading order in alpha_s(Q^2), including summations of all leading and subleading logarithms of Q^2 and 1/x in a way consistent with momentum conservation. We perform a detailed comparison to the 1993 HERA data, and show that they may be used to determine alpha_s(M_Z^2)=0.120 pm 0.005(exp) pm 0.009(th). The theoretical error is dominated by the renormalization and factorization scheme ambiguities.Comment: 24 pages, TeX with harvmac and epsf, 10 figures in compressed postscript. Final (published) versio

Comparison of numerical solutions for Q^2 evolution equations

Q^2 evolution equations are important not only for describing hadron reactions in accelerator experiments but also for investigating ultrahigh-energy cosmic rays. The standard ones are called DGLAP evolution equations, which are integrodifferential equations. There are methods for solving the Q^2 evolution equations for parton-distribution and fragmentation functions. Because the equations cannot be solved analytically, various methods have been developed for the numerical solution. We compare brute-force, Laguerre-polynomial, and Mellin-transformation methods particularly by focusing on the numerical accuracy and computational efficiency. An efficient solution could be used, for example, in the studies of a top-down scenario for the ultrahigh-energy cosmic rays.Comment: 12 pages, LaTeX, 13 eps files, Journal of Computational Physics in press, http://hs.phys.saga-u.ac.j