GEANT4 Simulation
Introduction
This Monte-Carlo simulation code for Proton charge Radius (PRad) experiment is based on the toolkit for GEometry ANd Tracking 4 (GEANT4).
Two independent event generators are used to generate the events from elastic electron-proton scatterings and electron-electron scatterings with radiative corrections.
Output data from the simulation consist of 1728 ADC channels from the Hybrid Calorimeter (HyCal) and position information from the Gas Electron Multiplier (GEM). Trigger is set to be the total energy sum on HyCal > 500 MeV (for 1.1 GeV incident beam), or > 1000 MeV (for 2.2 GeV incident beam).
The reconstruction program will reconstruct the clusters on HyCal, and do coincidence with GEM, then reconstruct the track with these two detectors.
The extraction program will analyze the reconstructed events, bin the cross sections data, and finally extract the proton charge radius.
Geometries
It shows the current geometries in the simulation code Geometries.pdf, including:
1. Target Cell and its gas inlet
2. Vacuum Box and its curve shape window
3. Vacuum pipe and flange
4. Gas electron multiplier (less detailed)
5. HyCal, HyCal Box, HyCal collimators
Physics List
GEANT4 StandardEM physics list is used.
The step of multiple scattering (SetStepLimitType) is set to be 'fMinimal'
Event Generators
Two independent event generators are used：
1. M. Meziane, I. Akushevich, and A. Ilyichev.
2. A. Gramolin ESEPP for elastic ep and Moller Part.
Output and Reconstructions
The code will output two files "EnergyDeposit.dat" and "GEMPosition.dat", they are both in text format.
EnergyDeposit.dat is the output of HyCal, shows the energy deposit of each channel if it is larger than 1 MeV.
GEMPosition.dat is the output of GEM, it shows each hit on GEM with a resolution of 0.1 mm.
Simulation Results
To be updated
