SHMS Single arm Monte Carlo

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Source code

  • Version control of mc_shms_single has moved from tarball to git. is used to store the code. (Useful git instructions/howto.)
    • To checkout and contribute using github:
      • Create an account on and following the directions for storing your public ssh key on the site.
        • NOTE: The github instructions ask you to install a program called "xclip" to help upload your public key. This is unnecessary - you can just "click and paste".
      • Once you have signed into github then go to
        • Select Watch to be notified of changes to mc_shms_single repo and the click on the Fork button to create your own Github copy of the repo.
      • On the computer that you want to run the code type: git clone where Githib-Username is your github username.
      • Now "origin" remote is to your personal Github repository. After cloning you will be in the "master" branch. Make your local changes and commit them to your local copy. You can update the github repository by command: git push origin master . If you want to have these changes incorporated into the JeffersonLab repository then go to your github account Githib-Username/mc_shms_single and click on the pull request button. This will notify the person monitoring the JeffersonLab repository and your changes can be pulled in.
      • To have access to the changes in the JeffersonLab GutHub repository, in your newly created mc_shms_single directory
        • One time need to execute the command: git remote add upstream
        • The command git fetch upstream will fetch any new changes from the original repository
        • The command git merge upstream/master will merge any changes fetched into your working files
    • When compiling code need on JLab ifarm machines need to do:"setup cernlib/2005" to set CERN_ROOT properly.
  • mc_shms_single Git repo on the web.
  • For historical reasons, mc_shms_single_april2012.tar.gz is the tarball. Discussion of the changes made to code.
  • On JLab ifarm64 machines execute : "setup cernlib/2005" before doing ""

Comments on code

  • Designed to be used for studying optics and acceptance of the SHMS.
  • Materials hit when multiple scattering flag turned on.
    • Target
      • When target length greater than 3cm, assumes a beer can target with diameter of 3.37cm and wall thickness of 0.005 inches
      • Need to enter the radiation length of target material in the input file.
    • Scattering chamber window is 0.016inches of aluminum
    • 15 cm of air between scattering chamber and snout. Since snout is not designed this is a guess.
    • SHMS entrance window is 0.020 inches of aluminum.
    • SHMS exit window is 0.020 inches of aluminum.
    • Three options for after the SHMS exit window
      • Argon/Neon Cerenkov. Set the cer_flag=1 ( line 22 in input file). The vac_flag ( line 23 in input file) is ignored.
      • Helium bag replaces the Argon/Neon Cerenkov. This is the assumed mode of option at low momentum. Set the cer_flag=0 ( line 22 in input file) and set the vac_flag=0 ( line 23 in input file).
      • For study, vacuum pipe replaces the Argon/Neon Cerenkov. Set the cer_flag=0 ( line 22 in input file) and set the vac_flag=1 ( line 23 in input file).
    • SHMS wire chambers
  • SHMS wire chamber resolution is 200 microns
  • SHMS collimator is in place and cuts events.
  • Events cut if outside area of drift chambers, S1 and S2 scintillators and the calorimeter in mc_shms_hut.f.
  • Dipole apertures used in the MC model: The following figures describe how to calculate the parameters required to describe the dipole apertures in the MC. The dipole effective length is divided into 8 equal segments and the aperture center and inclinations are calculated at each of these segments. The inclinations angles are shown in angles, and the drift distances and offsets of the center of the aperture with respect to the central trajectory are shown in table of offsets (20 cm drop) and (26 cm drop)