1. VETO Analysis Update Michael Wood University of Massachusetts, Amherst Outline Introduction and basics Reconstruction packages Efficiencies Simulation package Summary

2. Introduction The VETO system consisted of 12 scintillator paddles with a PMT at the top and bottom of each counter. The signal from each PMT was sent to both an ADC and TDC. Raw ADC counts ADC counts with TDC coincidence

3. Calibrations Timing calibrations are completed. The TDC offsets were determined from time differences between VETO and HYCAL (HTRIGT). The ADC threshold per counter was set in software with the MIP from a pair production run. The y-position is determined from the time difference between the top and bottom signals of each counter. To convert from time difference to distance (ie calculating the effective velocity), the VETO time difference was plotted versus the HYCAL y-position. Time-walk corrections were determined by fits to distributions of ADC versus TDC (work done by Dan Pomeroy).

4. y Reconstruction Resolution in y : +/-4 cm

5. Time-walk Corrections TDC = A – B/(ADC – C) Uncorrected ADC vs TDC Corrected ADC vs TDC Functional form of the time-walk correction

6. Reconstruction VETOHIT reconstruction The raw ADC and TDC information is stored in the VETOA and VETOT banks. Physical information such as x, y, time, etc are stored in the VETOHIT bank. The reconstruction software is in the veto library ($PRIMEX_SOURCE/library/veto). The y-position is calculated from the time difference between the top and bottom. Here is the criteria for a good VETO hit: Top and bottom TDC and ADC hits Software ADC threshold cut Top and bottom TDC time matching Timing cut on both TDCs VETO2HYCAL reconstruction Software to match hits in VETOHIT and HYCALCLUSTER banks ($PRIMEX_SOURCE/library/detector_match). Fills entry HYCALCLUSTER.veto. Values for a match: 1: x-position 2: time (+/-5ns) and x-position 3: y-position (+/-10ns) and x-position 4: x-position, y-position, and time matching

7. Efficiencies To calculate the efficiencies of each VETO counter, the number of hits in the VETO was divided by the number of hits in the HYCAL. Two separate efficiencies have been determined, one for charged-particle detection and one for neutral-particle misidetification. For the charged-particle case, a pair production run was analyzed. For the neutral-particle case, the snake-scan calibration runs at the end of the experiment were utilized. These runs were 5334 to 5410. The one disadvantage with the pair production run is that the e+ e- particles were in the horizontal plane (y=0). However, the calibration runs had the beam incident on every HYCAL element so a y-dependent efficiency can be determined.

8. Charged-Particle Efficiency Event selection Energy conservation  cut

9. Neutral-Particle Efficiency x (cm) InterceptSlope-350.010 2.67x10 -5 -250.011 1.96x10 -5 -150.010 -1.84x10 -5 -50.008 -1.9x10 -5 50.011 -1.71x10 -5 150.010 -1.53x10 -5 250.010 350.011 -6.31x10 -6 Results are from x- and y-position matching. No time matching. Analysis with HYCAL Pb-glass is currently underway.

10. Simulation Package The experimental charged and neutral particle efficiencies will be incorporated into Primex simulation packages. Generator – primsim The reaction channels appear well-developed. Test case: generated  0 decay to two photons events. The fiducial acceptance was ~60%. The overall neutral-particle efficiency was 1.8%. Detector simulation – psim_digitize The VETO functions are in the file VetoCounterSim.cc. This package creates VETOA and VETOT banks from the MCPART and MCDEPOSITED banks. I am currently rewriting this package to align the numbering scheme with codaIO library and add functions to apply both efficiency results. What is missing? The MCPART bank does not contain particle charge.

11. Summary  Time and y-position calibrations done  ADC calibration in progress  Reconstruction cuts under control  Charged-particle eff ~ 96%  Neutral-particle eff ~ 1%  Extending neutral-particle eff analysis to Pb-glass region  VETOHIT code to allow for ADC/TDC combinations  Currently reworking VETO simulation software