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Manuscript Title: rhad: a program for the evaluation of the hadronic R-ratio in the perturbative regime of QCD.
Authors: R.V. Harlander, M. Steinhauser
Program title: rhad
Catalogue identifier: ADRT_v1_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 153(2003)244
Programming language: Fortran.
Operating system: Alpha, Linux, Solaris.
Keywords: Hadronic R-ratio, Perturbative QCD, Electron-positron annihilation, Running and decoupling of alphas, Elementary particle physics.
Classification: 11.5.

Nature of problem:
The hadronic R-ratio R(s) is a fundamental quantity in high energy physics. It is defined as the ratio of the inclusive cross section sigma(e+e- -> hadrons) and the point cross section sigmapt = 4 pi alpha**2/(3s). It is well-defined both from the experimental and the theoretical side. R(s) belongs to the few physical quantities for which high-order perturbative calculations have been performed (partial results up to order alphas**4 exist!). Mass effects from real and virtual quarks, the evolution of the MSbar parameters, in particular in the presence of thresholds, and other subtleties lead to fairly complex results in high orders. Thus it is important to provide a comprehensive collection of formulas in order to make them available to non-experts.

Solution method:
rhad is a compilation of all currently available perturbative QCD corrections to the quantity R(s). Several options are provided which allow for a flexible use. In addition, rhad contains routines which perform the running and decoupling of the strong coupling constant. Thus only the center-of-mass energy has to be provided in order to determine R(s).

The applicability of rhad is restricted to the perturbative energy regions and does not cover the narrow and broad resonances.

Running time:
The typical runtime is of the order of fractions of a second.