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.