Compton Study from Experimental Data

1. Compton Study from Experimental Data Kelli Hardy

2. 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. Kelli Hardy

3. 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 Kelli Hardy

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

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

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

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

8. 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, Df and minimum angular separation cuts Kelli Hardy

9. 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 Kelli Hardy

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

11. 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 Kelli Hardy

12. 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 Kelli Hardy

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

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

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

16. 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 Kelli Hardy

17. 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. Kelli Hardy