Simulation Code

A Monte Carlo code developed by Cherniaten and Chikanian [1] was used to simulate the CSC response. The Monte Carlo code does the following:

• creates primary electrons in the gas volume of the CSC chamber
• diffuses the electrons as they drift to the anode wire
• shifts the electron positions according to the Lorentz angle, incident angle of the track, and angle of the strips with respect to the anode wires
• multiplies the number of electrons at the anode wire according to the gain of the chamber
• induces the charge on the cathode strips and then
• adds electronic noise and calibration uncertainty to the cathode charge measurements

After the total charge has been deposited onto the cathode strips, the charge distribution is fit and the centroid position is compared to the initial position of the track. The original code extracted the centroids using a center of gravity calculation and a gaussian fitting calculation. A fit using the Mathieson function [2], which more accurately represents the charge distribution on the strips and has been shown to produce better centroid measurements of [3] strips has been added to the code.

The input parameters to the code, and the baseline values are listed here:

• strip width - 0.5 cm, 1.0 cm readout
• anode-cathode spacing - 3.175 mm
• anode wire spacing - 5.0 mm
• gain - 1.0e5 (should be 2.0E4 for true baseline)
• # primary electrons/mm - 5.2/mm
• Lorentz angle - 8 degrees/0.8 T, B=0.3T
• electron range - 0.055 mm
• diffusion/mm drift - 0.051/mm
• charge collection time - 500 ns
• rms noise - 5000 electrons (should be 3000 for true baseline)
• rms noise from calibration errors - 0.005 (fractional)
• incident theta angle - 22.5 degrees
• incident phi angles - 11 degrees
• angle of strips - 0 degrees

The orientation of our endcap chambers, with respect to the global coordinate frame is shown in Figure 1.

 
Figure 1: The orientation of our CSC chambers with respect to the global coordinate system and the magnetic field.