TRT HT middle bit tuning


Middle bit of TRT high threshold bits can be used to reduce TRT occupancy under higher instantaneous luminosity condition during Run 2. Since high threshold bit pattern distribution is not modeled well in simulation (specifically digitization), HT middle bit fraction is lower in MC about 3 - 10% depending on the TRT parts.

HT middle bit fraction ≡ number of HT hits with middle HT bit high / number of total HT hits


Since HT variables are sensitive to pile-up, low <mu> data (<mu>~6) was selected for the study. Although HT bit pattern distribution of electron and muon is very similar, we studied both electron and muon for completeness.

  • Data
    • data11_7TeV.periodD.physics_Egamma.PhysCont.DESD_SGLEL.repro09_v01/
    • data11_7TeV.periodG.physics_Egamma.PhysCont.DESD_SGLEL.repro09_v01/
    • data11_7TeV.periodI.physics_Egamma.PhysCont.DESD_SGLEL.repro09_v01/
  • MC
    • J/ψ → μμ sample
      • mc11_7TeV.108494.Pythia_directJpsimu2p5mu2p5.merge.HITS.e835_s1310_s1300/
    • Z → ee sample
      • mc11_7TeV.147770.Sherpa_CT10_Zee.merge.HITS.e1443_s1372_s1370/


Athena software release to process data and MC are different since data was processed with old release and MC has to be reprocessed with various TRT digitizations.

  • for data
  • for MC


Two TRT_Digitization tags which are related to the study.

  • TRT_Digitization-01-00-14
    • The baseline TRT digitization tag for tuning study.
    • (Most) tuning parameters are overrided in
    • HT shaping is tabulated in '' and has to be hard-coded.
  • TRT_Digitization-01-00-24
    • The tag which all final tuning parameters are implemented.

HT middle bit tuning

List of tuning parameters

  1. High threshold shaping function
  2. High threshold value
  3. High threshold ΔT0 shift

Tuning of high threshold shaping function

The ASBDLR has a separate discriminators for tracking (low threshold) and TR photon (high threshold). High threshold discriminator has an additional shaping circuitry with a peaking time of 11ns to preserve signal uniformity. The HT signal has to be stretched to increase HT middle bit fraction as shown below. New HT shape (HT shape 3) has slower falling time than origianl HT shape and peaking time also delayed about 1.5 ns.


The Figure below shows the agreement of HT middle bit fraction between data and MC as a function of HT ΔT0 shift for different TRT partitions. HT middle bit fraction is always underestimated with original HT shape for all HT ΔT0 shifts. HT shape 3 is sufficiently large to have a perfect data/MC agreement.


Tuning of high threshold value

High threshold has to be tuned to restore an increased HT probability due to the new HT shape. HT probability increased 8.9% for Barrel short straws, 9.8% for Barrel long straws, 8.0% for Endcap A-wheels and 6.9% for Endcap B-wheels as shown in below figure. High threshold values are raised to restore original HT probability for each TRT partitions.


Tuning of high threshold ΔT0 shift

Generally HT signal is


HT bit pattern distribution


Final results

HT middle bit fraction vs. straw layer


HT bit pattern distribution



-- KyungeonChoi - 2015-06-16
Topic attachments
I Attachment History Action Size Date Who Comment
PDFpdf HTshape.pdf r1 manage 15.8 K 2015-06-17 - 09:34 KyungeonChoi HT shape all
PDFpdf final_HTbitpattern.pdf r1 manage 124.2 K 2015-06-17 - 10:46 KyungeonChoi  
PDFpdf final_HTmiddleBitfraction.pdf r1 manage 167.1 K 2015-06-17 - 10:42 KyungeonChoi  
PDFpdf tuningHLthreshold_HTprob.pdf r1 manage 189.6 K 2015-06-17 - 10:04 KyungeonChoi  
PDFpdf tuningHTdeltaT0.pdf r1 manage 415.1 K 2015-06-17 - 10:36 KyungeonChoi  
PDFpdf tuningHTdeltaT0_HTbitpattern.pdf r1 manage 382.0 K 2015-06-17 - 10:37 KyungeonChoi  
PDFpdf tuningHTshape.pdf r1 manage 116.5 K 2015-06-17 - 09:45 KyungeonChoi  
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Topic revision: r3 - 2015-06-17 - KyungeonChoi
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