1. Kelli Hardy Compton Study from Experimental Data

2. Kelli Hardy Purpose: To show that method for selecting single arm Compton events works on real Compton data and to see if we can qualitatively see single arm Compton events in production runs.

3. Kelli Hardy Double-Arm (Tested on dedicated Compton run # 4658) Procedure for selecting Compton events: Events in which: 2 clusters in HyCal Timing difference between trigger and tagger was less than 5ns (Timing cut) (see Figures 1&2) Sum of the two clusters was greater than 0.5Gev (Energy cut) (Radial cut): 4 cm< r< 34cm Figure 1: Timing difference between tagger and trigger

4. Kelli Hardy Double-Arm Figure 2: Timing difference between tagger and trigger From analysis of timing coincidence plot, a timing window of 5ns was taken. (As result T-counter 9 was excluded)

5. Kelli Hardy Double-Arm Figure 3: Energy sum of two clusters minus reconstructed tagger energy

6. Kelli Hardy Double-Arm Figure 4:  distribution After taking elasticity and minimum cluster separation cuts, get  peak at ~180 º.

7. Kelli Hardy Double-Arm Blue dots correspond to photons and red dot correspond to electrons. Figure 5: Kinematic correlation between cluster energy and cluster angle

8. Kelli Hardy Double-Arm After applying Compton kinematic cuts, a peak at ~1 is obtained indicating Compton events. This shows the method for selecting Compton events works for double-arm case. Figure 6: Pure Compton events after elasticity,  and minimum angular separation cuts

9. Kelli Hardy Single-arm Compton Used same procedure for selecting double arm Compton events with exception of: Select events with 1 cluster Assume all events are Compton Figure 7: Sign of single arm Compton events in production run

10. Kelli Hardy Single-arm Compton Figure 8: Energy Ratio from production run with r > 6cm

11. Kelli Hardy Single-arm Compton Background decreases with increasing radial cut, but Compton events are also cut out. Figure 9: Energy Ratio from production run with r > 8cm

12. Kelli Hardy Double-arm Compton in Production Data Purpose: To search for double-arm Compton events produced off of the vacuum window of pair spectrometer magnet in production data. Procedure: Same procedure for selecting Compton events in dedicated Compton run was used, with the following exceptions: Pion invariant mass cut (Z measured from target) Z measured from window

13. Kelli Hardy Double-arm Compton in Production Data Figure 10: Elasticity plot with arrow indicating possible double arm Compton events at ~ 0

14. Kelli Hardy Double-arm Compton in Production Data Small peak ~0.135 Gev shows pion invariant mass. Figure 11: M  invariant mass distribution where is the opening angle between the two photons.

15. Kelli Hardy Double-arm Compton in Production Data After cutting elasticity and pion invariant mass, a  distribution with peak around 180º is seen. Figure 12:  distribution with peak~ 180º

16. Kelli Hardy Double-arm Compton in Production Data Plot was made of cluster energy vs. cluster angle to look for possible indications of double arm Compton events. Two different colors correspond to the two different clusters. Figure 13: Kinematic correlation between cluster energy and cluster angle

17. Kelli Hardy Summary Qualitatively, plot for single-arm Compton agrees with plots shown earlier. We have good chance to isolate single-arm Compton events, however work is needed to understand how this process can be used for the following two purposes: To use this process to monitor Hycal gain To monitor efficiency of whole experimental setup There seems to be indication of Compton double- arm events produced off of the pair spectrometer vacuum window.