QUEEG: A Monte Carlo Event Generator for Quasielastic Scattering on Deuterium

We have developed a simulation of quasielastic electron scattering off nucleons in deuterium. The original code was developed by J.Lachniet for the analysis of the CLAS6 GM experiment. The Fermi motion of the nucleons creates an effective beam energy different from the laboratory one as seen from the rest frame of the moving nucleon. This effective beam energy is used with the Hulthen distribution (for the magnitude of the Fermi motion) and the elastic form factors (for the elastic scattering in the nucleon rest frame) to calculate a relative probability as a function of the Fermi momentum pf and θN , the direction of the moving nucleon relative to the beam. The Fermi 3-momentum ~ pf is selected randomly from this distribution, the electron scattering angle is chosen from the nucleon rest frame and boosted back to the lab. An option was added to QUEEG to include an asymmetric distribution in the azimuthal angle between the scattering plane (defined the incoming and scattered electrons) and the reaction plane (defined by the final nucleon momenta). Another option simulates a realistic event vertex distribution for a cylindrical target. Examples of the use of the event generator are shown. The source and Makefiles are available in the CLAS12 repository. CLAS12 Note 2014-007