Double-Arm Compton Analysis

• February 22, 2007
• March 1, 2007
• March 8, 2007
• March 22, 2007

February 22, 2007

Here is some information on the double-arm compton analysis which is used to check the single-arm compton analysis.

I used the cuts from Yelena's analysis to select the events.

Here is a plot of the elasticity which is the 1 minus the quantity of the sum of energies of the pair of clusters divided by the incident photon energy. I narrowed the cut on elasticity to +/-0.05.

Here is the reconstructed z-position from the compton pair.

Here is the difference in phi angles between the compton pair.

My plan is to fit the phi angle difference, subtract the background, and extract the yield.

Here are the fits for each T-counter where the top. left plot is the sum of all T-counters.

Here is a plot of the normalized yield(counts/photon flux) by T-counter.

March 1, 2007

I talked with Yelena about my results. She recommended to calculate the total cros section similar to what she does. She was unsure how I was calculatingthe solid angle and applying a bin angular bin width.

This is a plot of the acceptance corrected total cross sections.

• Black circles - pi0 prod. run
• Red squares - compton run (single-arm)
• Blue triangles - compton run (double-arm)
• Black line - Klein-Nishina total cross section

March 8, 2007

At the last collaboration meeting, I claimed that my acceptance calculations for single-arm and double-arm compton were the same. The geometrical acceptance was 6.1% whenthe angular range for detecting the scattered photon was 0.5-0.9deg.

I investigated this further by analyzing the different hit combinations in the simulation. I tallied the 4 cases where both the photon and electron are detected in HyCal, the photon is detected and the electron is missed, the photon is missed and the electron is detected, and both particles are missed. The table below shows the results.

The total number of generated events was 12353.

The conclusion from the second row is that within the small angular acceptance of 0.5-0.9deg, there are no events where the electron is missed.

March 22, 2007

I made some more tests on the differences in the yields from a dedicated compton run when analyzed with single-arm and double-arm techniques.

Here is a plot of the energy ratio from the single-arm analysis. The legend is

• Black - all events with number of clusters >= 1.
• Red - events with 1 cluster.
• Blue - events with 2 clusters.
• Magenta - events with 2 clusters where both are photons.

Here is the legend for the next two plots:

• Black circles - pi0 prod. run
• Red squares - compton run (single-arm)
• Blue triangles - compton run (double-arm)
• Black line - Klein-Nishina total cross section

For this study, I threw out events with only 1 cluster and events that did not have an electron identified by the veto.

In this plot, I went back to my loose analysis on the single-arm, but removed the veto cut from the double-arm analysis.