Events are generated by a generator program that simulates the hard scattering process. The output of the generator is passed through a program simulating the hadronization. The generated particles are then passed through the detector simulation and finally through the trigger simulation program.
The hard scattering process is simulated by DJANGO [25], version . The event generator DJANGO simulates deep inelastic lepton-proton scattering including both QED and QCD radiative effects. DJANGO is an interface of the Monte Carlo programs HERACLES [26] version and LEPTO [27] version .
The structure function sets used are MRSA [6]. The initial and final state QCD cascade is simulated using the color dipole model ( CDM) [28] as implemented in the program Ariadne (version ) [29]. The hadronization of the final state uses the LUND string fragmentation model [30] implemented in the program JETSET (version ) [31].
The detector simulation is performed by the standard ZEUS simulation program MOZART [32]. This program is based on GEANT [33] (version ) and incorporates a detailed description of the ZEUS detector, including inactive material. The detector responses have, where necessary, been tuned to test-beam data. The output of this detector simulation program is fed into ZGANA, which simulates in software the ZEUS trigger system.
Events are generated with and for .
The event vertex distribution is determined from a sample of photoproduction data taken in the period for which we analyze the charged current data. For these events the vertex finding efficiency is high and no bias on the distribution of the position of the vertex is introduced.
We generate events which corresponds to a total luminosity of .