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The Mott Group has a GEANT4 simulation of the JLab MeV Mott Polarimeter. This simulation was built from 2014-2016 simultaneous to the upgrade efforts on the polarimeter. The primary purpose of this simulation is to determine, from first principles, the shape of the effective Sherman function with respect to target thickness. This page serves a few purposes: it provides links to the relevant references for simulation users, provides a brief tutorial, and shows results. Additionally, this page may serve as a place to indicate what work is being done or needs to be done on the simulation.

Where To Find the Simulation

  • A working version is maintained on the ifarm computers CUE in the directory /group/mottgrp/MottG4/.
  • To use this, the user must set the environment variable $MOTTG4DIR to /path/to/MottG4/ before using the simulation.
  • Additionally, the user must have access to cmake version 2.8 or later.
  • The current version is maintained at github for those who want the model on their personal computers or some other location for development purposes. Contact Martin McHugh at for access to this repository.


The best way to get started is to read the

    • Tutorial slides

Herein lies all that Marty McHugh has written about the Mott GEANT4 simulation:

External sources of interest:

Future Work: A Suggested To Do List

  • Get Xavier's calculations for gold and other nuclei of interest on a 100-250 keV over the whole range of energies (approx. 2-10 MeV)
    • Integrate this into the exiting interpolation method in
    • Perform calculations for target foil thickness extrapolation based on final Run 2 parameters:
      • Scattering Angle
      • KE = 4.9 MeV.
      • Final thickness measurments from Marcy.
  • Build Mott Physics Class (single scattering based on Xavier's data). (Low priority)