Lumi Sim

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This page discusses the details of the specific implementation of the luminosity monitoring system into the eRHIC IR. Details on the implementation of the simulation setup inside the EicRoot framework is also shown here.

Simulation Scripts

Details on running a simulation in the EicRoot framework can be found here. The process is started by running scripts to define the detector setup. As discussed in on the lumi requirements page, the setup selected for the luminosity monitoring system consists of a zero degree calorimeter and a pair spectrometer. Thus the detector system will consist of three calorimeters, one at zero degrees, and two separated vertically to register conversion electrons from the pair spectrometer. The calorimeters are separated vertically in order to be out of the primary synchrotron radiation fan from the bending electron beam.

Technically, the detectors are constructed from three different scripts named calorimeter_center.C, calorimeter_down.C, and calorimeter_up.C (found in the directory /direct/eic+data/rmpetti/eicroot/tutorials/designer/luminometer). The output of these scripts are root files that contain the detector geometry definitions and are used as input to the simulation.

A magnetic field also needs to be installed as part of the pair spectrometer. A simple dipole field is implemented in the format described here. The file can be found at /direct/eic+data/rmpetti/eicroot/input/IR/PHOTON/dipole_60cm_0_5T_bigGrid_old.csv and can be registered with the simulation by following the instructions in that section.

Lastly, for the full setup in the IR, a converter end cap at the end of the beam line for the photons is placed in the simulation. Some information related to the construction of beam pipe in between magnet elements in the IR can be found on the [beampipe construction] page.

After setting up the detectors, magnetic field, and beam pipe, it is time to start the physics simulation. Import events from your generator of choice (DJANGOH, or the in house simple event generator found at ) and push everything through GEANT tracking in EicRoot by running the simulation.C script. An example used for the luminosity monitor simulations can be found at