Home » Blogs » genevb's blog

GMT alignment: cosmic ray data

Updated on Thu, 2015-01-08 14:24. Originally created by genevb on 2015-01-08 14:24.
  • Dataset needs:
    • Ideally: perhaps a few thousand (~5k-10k) good tracks per GMT module
    • Minimally: perhaps ~1k tracks per GMT module
    • Past experience: ~1 million cosmic rays per hour traversing TPC
      • Scaling by GMT area over that of the TPC (~0.01 m2 vs. ~25 m2), we expect about 10k tracks in a horizontal GMT module per day.
      • GMT modules are at 2 o'clock and 5 o'clock positions: some reduction in rate from not being straight up and down, particlarly for the 2 o'clock position: perhaps ~2k-3k per day for modues at 2 o'clock, and 5k-7k per day for modules at 5 o'clock.
      • Quality cuts of the TPC tracks likely cause another order of magnitude reduction: minimally only a few hundred events per module per day.
    • Conclusion: would really need to run for a couple weeks of un-prescaled, efficiently-triggered events to get a few thousand tracks per module, but 5 full days may prove minimally sufficient.
  • Trigger needs:
    • TOF-triggered cosmic ray data actually biases against GMT, as TOF modules are where the GMT is not (hits only come from shower events)
    • GMT itself is not trigger-able (hardware was not installed)
    • Zerobias does not work: TPC tracks Z position unknown
    • MTD-triggered cosmic rays have potential
      • MTD has noise, but an MTD coincidence may be low on noise. This can be tested once gas is turned on (MTD gas turns on at same time as TPC gas). [Lijuan]
        • If the coincidence trigger rate is low, we are fine.
        • If the coincidence trigger rate is high, prescaling would be needed, which would inversely impact that amount of time necessary to acquire the needed dataset (signal gets prescaled along with noise)
      • MTD module pairs could be selected which give best chance of having a GMT hit
    • MTD-TOF-coincidence-triggered cosmic rays have potential
      • Coincidence of MTD tray at near a GMT with a TOF tray (group of trays?) on the opposite side of STAR
    • Is MTD-TOF-MTD-coincidence possible?
      • TOF opposite GMT
      • Triple coincidence noise rate must be small???
    • Further data reduction (helpful for minimizing the junk data stored and analyzed) possible with HLT veto. Two possibilities:
      • GMT hit requirement: very simple for HLT if GMT hit collection can be provided to them (GMT hits > 0 ? keep : veto)
        • Needs pedestal subtraction for GMTs. Is this available with reasonable quality?
      • TPC track requirement: HLT finds at least a single TPC track projecting within some window (with large margins) around the GMT modules
        • Needs small effort to set up HLT projection to GMT
    • Conclusion: need to find out coincidence trigger rates once gas is in, but there are likely options which may have different noise rates; those options would need to each be implemented and rate-checked; vetoing by HLT may be helpful to speed up analysis, but needs investigated
  • TPC:
    • Run with gating grid (GG) always open, allowing for near-endcap tracks
      • Pedestals must be taken in this condition during cosmic data-taking as there is a dependence on the opening of the GG.

-Gene

»