1. COMPTON SCATTERING IN FORWARD DIRECTION
PROGRESS REPORT
PAWEL AMBROZEWICZ
NC A&T

2. GOAL – EXTRACT COMPTON CROSS SECTION WITH GOOD PRECISION
KINEMATIC TOOLS
EVENT SELECTION
YIELD FITS
SIMULATION
CROSS SECTIONS
SUMMARY

3. RECONSTRUCTED QUANTITIES:
KINEMATICS
MEASURED QUANTITIES:
ENERGY OF INCIDENT PARTICLES
POSITIONS AT HyCal FOR BOTH PARTICLES
ENERGIES OF SCATTERED PARTICLES
RECONSTRUCTED QUANTITIES:
DISTANCE TO TARGET (Z):
REQUIRES KNOWLEDGE OF x, y, E FOR BOTH CLUSTERS
ENERGY DIFFERENCE ( E(TAGGER) - E(E1, E2, ) ):
REQUIRES KNOWLEDGE OF ENERGIES FOR BOTH CLUSTERS
AND OPENING ANGLE

4. CO-PLANARITY |-180o|<25o FIDUCIAL REGION OF HyCal :
EVENT SELECTION:
COINCIDENCE TIMING < 3.2 ns
CO-PLANARITY |-180o|<25o
FIDUCIAL REGION OF HyCal :
2+ INNER CRYSTAL LAYERS
OUTERMOST CRYSTAL LAYER
“CRISS-CROSS” PAIR PRODUCTION CUT
’e’ OPENING ANGLE  RMIN > 18.5 cm

5. EVENT SELECTION: MINIMAL OPENING ANGLE/ MINIMAL SEPARATION CUT
ADDITIONAL CUTS SERVE
TO MINIMIZE
SIGNAL-TO-NOISE RATIO
TIMING CUT AFTER ALIGNMENT

7. RADIATIVE EFFECTS NEED TO BE
ACCOUNTED FOR 

8. TYPICAL DATA YIELD FITS

9. SIMULATION: GENERATES SIMPLE GEOMETRIC ACCEPTANCE
APPLIES POSITION SMEAR TO REPRODUCE
EXPERIMENTAL RESOLUTIONS
ACCOUNTS FOR THE BEAM POSITION OFFSETS

10. SIMULATION
ACCEPTANCE DEPENDENCE ON BEAM POSITION SHIFTS

13. ONGOING PARALLEL ANALYSIS – KELLI HARDY
MAIN DIFFERENCES:
FITS ONLY ENERGY DIFFERENCE
USES EMPTY TARGET AS BACKGROUND MODEL
DOES NOT REMOVE PAIR PRODUCTION EVENTS
USES GEANT TO GENERATE ACCEPTANCE

14. SYSTEMATIC ERROR ESTIMATION
STATISTICAL ERROR < 0.5%
SYSTEMATIC ERROR ESTIMATION
PHOTON FLUX %
TARGET THICKNESS %
BACKGROUND SUBTRACTION %
ACCEPTANCE ~2.0%
STABILITY (CALIBRATIONS) ~2.0%
TOTAL ~5%

15. SUMMARY
COMPTON CROSS SECTION HAS BEEN EXTRACTED FOR LARGE PORTION OF THE DATA – INDEPENDENT ANALYSES IN GOOD AGREEMENT
STUDY SHOWS THAT STABILITY OF THE CROSS SECTION IS ~5%
TO IMPROVE PRECISION MONTE CARLO SIMULATION HAS TO BE REFINED – CORRECTING FOR RADIATIVE EFFECTS NECESSARY
REMAINING COMPTON DATA HAS TO BE ANALYZED …
ANALYSIS NOTE – WORK IN PROGRESS …