In order to determine the efficiency of detecting charged particles with the Veto detectors, I analyzed one compton data run. The run number was 4871 which contained events from the 9Be target.
The following cuts were applied to isolate the true Compton scattering events from the background in the data
The figure below shows the distributions for the opening angle, energy conservation, and cluster seperation. In fact, the opening angle and cluster seperation are the same effect so only one cut was needed.
The next figure below are distributions of dPhi in the following order
The next figure below is of the x-position from the Veto detectors versus the x-position from HYCAL. The Veto detectors determine x by which counter was hit and assigned the x-position to be the center of the paddle. The narow width of the Veto x-positions is NOT due to resolution.
The next set of plots show the x-y distributions from the HYCAL detector for all clusters(top, left), charged particles determined by Veto(top, right), and neutral particles not found in Veto(bottom, left).
For the two cluster events, the figure below shows the charged particle combinations of cluster 1 and cluster 2. The total number of entries gives the number of compton events.
Next I added a timing cut between the photon time and the Veto hit time to be within 10ns. The sum of the 1 charged and 1 neutral particles gives the number of compton events determined by the Veto detectors. The result is about 25%.
