A Deuteron Quasielastic Event Simulation for CLAS12

An experiment to measure the neutron magnetic form factor ($G^M_n$) is planned for the new CLAS12 detector in Hall B at Jefferson Lab. This form factor is extracted from the ratio of quasielastic electron-neutron to electron-proton scattering off a liquid deuterium ($LD_2$) target. The QUasiElastic Event Generator (queeg) models the internal motion of the nucleons in deuterium. It extends a previous version used at Jefferson Lab.\footnote{J.D.Lachniet, PhD thesis, Carnegie-Mellon University, 2005.} The program generates events that are used as input to the Geant4 Monte Carlo (gemc); a program that simulates the particle's interactions with each component of CLAS12 including the target material. The source code for queeg was modified to produce output in the LUND format, set the position of the center of the $LD_2$ target, and simulate a realistic deuterium target. The event vertex was randomly distributed along the beamline in the target region and von Neumann rejection was used to select random points in the plane transverse to the beamline within a fixed radius from the beam. An initial study of the impact of the target structure and material revealed only limited effects.