TWIST Technote 79

Simulations of Multiple Scattering in the TWIST detector

Art Olin, 11 March 2003

The core of this report is a series of plots of multiple scattering distributions simulated for the TWIST spectrometer. These have been produced by analyzing simulation runs with positrons generated just outside the target foil for a range of discrete angles and momenta in a 2 T field. Space points from the simulated trajectory were sampled at the position of each detector plane, and compared with the ideal helical trajectory. RMS deviations of these distributions as well as gaussian fits were examined in the radial and azimuthal directions. In order to characterize these distributions in the plane normal to the trajectory I reduced the width in the detector azimuthal plane according to the pitch angle of the helix.

Following these figures is a technical explanation of how they were obtained and some of the implicit assumptions. Finally there is some discussion of the implications of these findings.