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Manuscript Title: The Monte Carlo program LESKO-F for deep inelastic e+-p -> e+-X scattering at HERA including QED bremsstrahlung from the lepton line.
Authors: S. Jadach, W. Placzek
Program title: LESKO-F version 2.2
Catalogue identifier: ACJZ_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 72(1992)221
Programming language: Fortran.
Computer: IBM 3090 300S VF.
Operating system: MVS/XA, JES3 WITH TSO.
RAM: 45K words
Word size: 32
Keywords: Particle physics, Elementary, Event simulation, Radiative corrections, Deep inelastic, Monte carlo simulation, Bremsstrahlung, Electrodynamics quantum (qed), Spin polarization, Electroweak theory, Structure functions.
Classification: 11.2.

Nature of problem:
In deep inelastic electron proton scattering the QED radiative corrections, in particular the effects due to bremsstrahlung from the lepton line, are well known, in some regions of the phase space, to be rather big, even of the order of 100 per cent. These effects have to be calculated if we want to extract physically significant information from the experimental data, e.g. for the measurement of the proton structure functions. The QED radiative effects, as it is generally known, depend substantially on the properties of the experimental set-up (resolutions, acceptance) and on the event selection criteria in the data analysis (triggers, cut-off's). A Monte Carlo event generator is a very helpful tool and the only one which is able to bring these important relations under control.

Solution method:
The Monte Carlo simulation of the process e+-p -> e+-X is applied to analyse the effects of bremsstrahlung from the lepton beam. The electron (positron) proton scattering process is described according to the parton model assumptions by hard lepton-quark sub-scattering which is mediated by the standard electroweak interactions i.e. photon and Z0 boson exchange. The photon emission from leptons is described in the framework of QED. Some realistic cuts are included at the level of the event generation and other ones may be imitated by rejecting some of the generated events.

The incoming e+- may have nonzero spin polarization. Single bremsstrahlung photon is emitted only from the lepton (initial and final states), not from the quark. QCD radiative effects are not included in the simulation, although the proton structure functions have a QCD-style scaling violation property. The structure of the M.C. algorithm allows to include QCD effects in the future.

Running time:
Efficiency is about 1200 events per IBM 3090 300S CPU second for parton distribution functions in Duke and Owens parametrization.