Difference between revisions of "CDC Hit Generation"

Revision as of 16:00, 6 May 2024

CDC Hits from CDCDigi Hits

• the code that converts raw hits from the fADC125s of the CDC into actual CDC Hits is done in several steps:
  • the code DCDCHit_factory_Calib.cc takes the raw CDCDigiHits and create CDCHits based on the raw information. In this process the pedestal is subtracted from the signal peak amplitude and the integral and in addition the amplitude is converted into an energy based on calibration data. A code snipet of this procedure is shown here:
    double amp = amp_a_scale*gain*double(maxamp);
  • In the following pictures the top row of 3 histograms shows the signal amplitude in ADC counts vs drift-time converted to ns (but not corrected for timing offsets) as reported by the FPGA of the fADC125. The left most graph shows the hits of channels in the same preamp crard if the total number of the hits in that card surpasses 14 hits. The middle one is the same for preamp hit multiplicity 10 to 14 while the right most shows hits from preamp carts with hits less than 10. The raw data is taken from DCDCDigiHit objects generated from DCDCPulse objects. The 2d histogram in the bottom row on the left is the signal amplitude vs drift time again, however these data were taken from the DCDCHit objects where a scale factor and gain correction is applied to the signal amplitude. That move the t0 peak close to 0 drift time. The location of this t0 drift time depends on the signal amplitude and is reported in the graph in the middle of the bottom row. A Gaussian is fit to the distribution to determine the location of t0. The error bars in the plot are the errors on the peak position of the fit.

Example Run 120594 without(left) and with(right) cut at 180 for raw adc signal peak

Example Run 72780 without(left) and with(right) cut at 180 for raw adc signal peak

Example Run 72840 without(left) and with(right) cut at 180 for raw adc signal peak

As expected the CDC Hit efficiency will drop and it drops more at larger drift distances. Below is a comparison of run 72840, first 10 files, without and with a cut of the CDC hit amplitude. At a drift distance of 7mm the drop is about 3.5% absolute.

Alexander A. analysis based on 20 files of a run from 2017 run period the finds:

• ver54 default /volatile/halld/home/aaustreg/RunPeriod-2017-01/monitoring/ver54/hists/merged/hd_root_030730.root
  • 7.76 rho / 1k triggers
  • 1.16 omega / 1k triggers
• ver55 CDC:CDC_HIT_THRESHOLD 180 /volatile/halld/home/aaustreg/RunPeriod-2017-01/monitoring/ver55/hists/merged/hd_root_030730.root
  • 8.22 rho / 1k triggers (+6%)
  • 1.22 omega / 1k triggers (+5%)