Editing Geant4 Cosmic Ray Detection Simulation (section)

==Geant4 Simulation==


===Two Scintillators===

In order to better simulate the real world,  a second scintillator was put into the simulation. Then, a second scoring volume variable and energy deposition variable were created. Header files had to be altered in order to allow for these variables to be created. Numerous methods in the runacction(), eventacction(), primarygeneratoraction(), and run() header files had to be duplicated to allow for more variables to be created. 


===Finding Theta===

Then, the angle had to be found. Using a triangle and finding the arctangent of the upper angle, theta of the experiment could be found. This theta in the simulation was the same one found in the actual experiment. Following the finding of theta, theta was plugged properly into the distribution used to find the energy of the particle shot out of the beam. When setting the particle energy, Geant automatically sets the energy in KeV. So, the energy needed to be multiplied by 1000. A two dimensional histogram was drawn to compare the energy deposition in the first scintillator versus theta. This is displayed below.


[[File:EnergyvTheta.png|center|frame|Two Dimensional Histogram of Energy Deposition versus Theta]]


===Finding Theta in a Different Manner===

This data had a greater curvature. The curvature in the Geant simulation was about 60%, whereas the curvature in the experiment was about 22%. Since the curvature was so much greater in the simulation, it was figured that much of the data in the actual experiment was being skewed by the resolution of the experiment. After this, it was decided that some of the difference in curvature was due to how theta was being measured in the simulation. In the experiment, theta was found using the difference between the top and bottom scintillators. However, in the Geant simulation, theta was found using just the top scintillator. So, another method to find theta using both scintillators was found and executed. This method involved picking a point randomly from the top scintillator and a point randomly from the bottom scintillator. Then, the momentum magnitude in the x direction was found to be the x location of the point on the bottom scintillator subtracted from the x location of the top scintillator. The y direction momentum was found in the same method as the x direction. The momentum in the z direction was just distance between the two scintillators. Finally, the slope was found in all three directions and traced back to the point where it should begin in order to hit both scintillators. This point was then used as the starting point for the particle in the simulation. After finding the starting position, a new theta was found using the two scintillators. The data, as shown below, did not yield the same results as the experiment. Even with the new method of finding theta, the simulation was still too accurate when compared with the experiment. 


[[File:EnergyvTheta8.png|center|frame|Two Dimensional Histogram of Energy Deposition versus Theta]]


===Changing Angle Distribution===


The next thing that needed to be changed was the run limit. Originally, Geant would not allow for more than 100 events per run, but by altering the vis.mac file from N=100 to N<0. This allowed for an unlimited number of events to be run per run. Another thing that had to be changed was the dependency of the angle coming in from the sun. This angle had a cosine squared dependency and was placed into the code in order to make the simulation more like the actual experiment.  An example of a run with this dependency implemented is shown below.


[[File:EnergyvTheta3.png|center|frame|Geant Simulation with Two Scintillators with Angles Coming in at Cosine Squared Distribution]]


===Finding the Proper Skew===


The final change that needed to be made was the final graph needed to be skewed in the simulation in order to get a run that was closer to the actual experiment. In order to implement the exact skew the actual experiment, the top and bottom data collected had a random Gauss fit number added to it. This made sure that the data was stretched out to be slightly tighter. The correct range was between 0 and 4 centimeters. An example of the graph with the skew is shown below. 


[[File:EnergyvTheta10.png|center|frame|Two Dimensional Histogram of Energy Deposition versus Theta with Skew]]