4,657 research outputs found
GENTLE/4fan v.2.0 - A Program for the Semi-Analytic Calculation of Predictions for the Process e+e- -> 4f
We describe version 2.0 of the Fortran program GENTLE/4fan for the
semi-analytic computation of cross-sections and distributions in four-fermion
production in e+e- annihilation. GENTLE/4fan covers all charged current and
neutral current our-fermion final states with no identical particles, no
electrons, and no electron neutrinos in the final state. Initial state
radiation representing the most relevant quantum corrections and anomalous
triple gauge boson couplings have been included.Comment: 38 pages, LaTex, 4 tables, uses fleqn.sty and elsart.cl
HECTOR 1.00 - A program for the calculation of QED, QCD and electroweak corrections to ep and lN deep inelastic neutral and charged current scattering
A description of the Fortran program HECTOR for a variety of semi-analytical
calculations of radiative QED, QCD, and electroweak corrections to the
double-differential cross sections of NC and CC deep inelastic charged lepton
proton (or lepton deuteron) scattering is presented. HECTOR originates from the
substantially improved and extended earlier programs HELIOS and TERAD91. It is
mainly intended for applications at HERA or LEPxLHC, but may be used also for
muon scattering in fixed target experiments. The QED corrections may be
calculated in different sets of variables: leptonic, hadronic, mixed,
Jaquet-Blondel, double angle etc. Besides the leading logarithmic approximation
up to order O(alpha^2), exact order O(alpha) corrections and inclusive soft
photon exponentiation are taken into account. The photoproduction region is
also covered.Comment: 74 pages, LaTex, 14 figures, 7 tables, a uuencoded file containing
the latex file and figures is available from: http://www.ifh.de/theory/ or on
request from e-mail: [email protected]
Resonance Propagation and Threshold Singularities
We consider the problem of propagation of an unstable particle in the
framework of Quantum Field Theory. Using unitarity, we show that a real
renormalization constant free of threshold singularities naturally arises.Comment: 5 pages, no figures, revte
Structure determination from powder data : Mogul and CASTEP
When solving the crystal structure of complex molecules from powder data, accurately locating the global minimum can be challenging, particularly where the number of internal degrees of freedom is large. The program Mogul provides a convenient means to access typical torsion angle ranges for fragments related to the molecule of interest. The impact that the application of modal torsion angle constraints has on the structure determination process of two structure solution attempts using DASH is presented. Once solved, accurate refinement of a molecular structure against powder data can also present challenges. Geometry optimisation using density functional theory in CASTEP is shown to be an effective means to locate hydrogen atom positions reliably and return a more accurate description of molecular conformation and intermolecular interactions than global optimisation and Rietveld refinement alone
Automated use of DIANA for two-fermion production at colliders
We describe packages for the calculation of radiative corrections to
two-fermion production at colliders. The packages use DIANA, and also QGRAF,
FORM, Fortran, and further unix/linux tools. The one-loop calculations in the
Standard Model are highly automatized with the package aITALC. Further, the
automatic determination of all the matrix elements for two-loop corrections to
massive Bhabha scattering in QED and the classification of their topologies and
prototypes is done with DIANA. A generalization to the Standard Model is
straightforward.Comment: To appear in the proceedings of ACAT03, Dec 2003, KEK, Japa
Four-fermion production with RACOONWW
RACOONWW is an event generator for e+e- --> WW --> 4fermions(+gamma) that
includes full tree-level predictions for e+e- --> 4f and e+e- --> 4f+gamma as
well as O(alpha) corrections to e+e- --> 4f in the so-called double-pole
approximation. We briefly sketch the concept of the calculation on which this
generator is based and present some numerical results.Comment: 9 pages, latex, 6 postscript files, to appear in the proceedings of
the UK Phenomenology Workshop on Collider Physics, Durham, UK, 19-24
September, 199
Standard SANC modules for NLO QCD Radiative Corrections to Single-top Production
It this paper we present the results obtained with the newly created Standard
SANC modules for calculation of the NLO QCD corrections to single top
production processes in s and t channels at the partonic level, as well as
top-decays. The main aim of these results is to prove the correct work of
modules. A comprehensive comparison with results of the CompHEP system is
given, where possible. These modules are intended to be used in Monte Carlo
generators for single top production processes at the LHC. As in our recent
paper, devoted to the electroweak corrections to these processes, we study the
regularization of the top-legs associated infrared divergences with aid of the
complex mass of the top quark. A comparison of QCD corrections with those
computed by the conventional method is presented both for top production and
decays. For s channel production we give an analytic proof of equivalence of
the two methods in the limit of low top width.Comment: 21 pages, 2 figures, 17 table
S-Matrix Approach to the Line Shape
We analyze the line shape assuming the existence of an analytic, unitary
S-matrix. As an example, from hadron production at LEP we determine
GeV, GeV. This is in accordance with earlier results after performing a shift
of the mass value of about MeV. The cross
section and related observables may be described by a small number of
additional degrees of freedom without relying on a specific field-theoretic
model.Comment: 9 pages, LaTex, 1 table, a uuencoded file containing the latex file
is available at ftp://ftp.ifh.de/pub/preprint/desy91-111.uu Note: paper
published in Phys. Lett. B273 (1991) 51
Electroweak Physics, Experimental Aspects
Collider measurements on electroweak physics are summarised. Although the
precision on some observables is very high, no deviation from the Standard
Model of electroweak interactions is observed. The data allow to set stringent
limits on some models for new physics.Comment: Plenary Talk at the UK Phenomenology Workshop on Collider Physics,
Durham, 199
Convex Hull of Arithmetic Automata
Arithmetic automata recognize infinite words of digits denoting
decompositions of real and integer vectors. These automata are known expressive
and efficient enough to represent the whole set of solutions of complex linear
constraints combining both integral and real variables. In this paper, the
closed convex hull of arithmetic automata is proved rational polyhedral.
Moreover an algorithm computing the linear constraints defining these convex
set is provided. Such an algorithm is useful for effectively extracting
geometrical properties of the whole set of solutions of complex constraints
symbolically represented by arithmetic automata
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