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Manuscript Title: JetViP 1.1: Calculating one- and two-jet cross sections with virtual photons in NLO QCD.
Authors: B. Potter
Program title: JetViP 1.1
Catalogue identifier: ADKC_v1_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 119(1999)45
Programming language: Fortran.
Computer: HP-Clusters.
Operating system: HP-UX, IRIX, LINUX.
RAM: 9M words
Keywords: Particle physics, Elementary, Event simulation, Chromodynamics quantum, Jet physics, Deeply inelastic Electron-proton (ep) and, Electron-photon (egamma), Scattering (dis), Photoproduction, Transition from Photoproduction to dis.
Classification: 11.2.

Nature of problem:
In eP- and egamma-scattering experiments, the hadronic final state can be analysed by jet cluster algorithms, yielding inclusive single- and dijet cross sections. These can be obtained in a continuous range of photon virtuality. The cross sections allow the extraction of parameters, such as alphas, Lambda MS(bar) or parton densities (also of the virtual photon), if the respective jet cross sections are theoretically known.

Solution method:
JetViP is a computer program for the calculation of inclusive single- and dijet cross sections in eP- and egamma-scattering in NLO QCD. The virtuality of the photon, radiated by the incoming electron, can be chosen in a continuous range, reaching from photoproduction into deep inelastic scattering. The various contributions to the full jet cross section, including the resolved photon contributions, are implemented. The calculation is based on the phase-space-slicing method. The multidimensional phase-space integration is performed with the help of the VEGAS Monte Carlo integration routine [1]. The parton distribution functions (PDFs) from the PDFLIB are used [2] and for the virtual photon PDF the two routines by Schuler and Sjostrand (SASGAM) [3] and by Gluck, Reya and Stratmann (GRS) [4] are used.

Running time:
Varies strongly from LO to NLO and depends on type of subprocess (direct or resolved). At LO, running times of about 1 minute for a cross section with fixed bin-size in one of the kinematical variables are typical. At NLO, the running time for such a cross section varies between 30 minutes (for the single resolved contributions) to 5 hours (for the double resolved contributions).

References:
[1] G.P. Lepage, J. Comp. Phys. 27 (1978) 192.
[2] H. Plothow-Besch, PDFLIB User's Manual. URL: http://consult.cern.ch/writeups/pdflib/
[3] G.A. Schuler, T. Sjostrand, Z. Phys. C68 (1995) 607; Phys. Lett. B 376 (1996) 193.
[4] M. Gluck, E. Reya, M. Stratmann, Phys. Rev. D54 (1996) 5515.