Difference: TRTHTmiddleBitTuing (5 vs. 6)

Revision 62015-06-19 - AndrewBeddall

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META TOPICPARENT name="KyungeonChoi"

TRT HT middle bit tuning


Introduction

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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, HT middle bit fraction is lower in MC about 3 - 10% depending on the TRT parts. The goal of this study is to tune TRT digitization to have a best data and simulation agreement. The definition of HT middle bit fraction is following.
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Using only the middle of the tree TRT high threshold (HT) bits reduces the effect of pileup under higher instantaneous luminosity conditions during Run 2. Discrepancies in the modelling (timing and width of the high level signal) results in a HT middle bit fraction lower in MC by 3 - 10% depending on the TRT region. Since TRT particle identification is now based on using only the middle HT bit, the goal of this study is to tune the TRT digitization to improve the agreement between data and simulation.
 
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HT middle bit fraction ≡ number of HT hits with middle HT bit high / number of total HT hits
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The definition of HT middle bit fraction, applied in any region of interest, is as follows:

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

 

Datasets

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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.
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Since HT variables are sensitive to pile-up, low <mu> data (<mu>~6) was selected for the study. Although the HT bit pattern distributions for electrons and muons are very similar, both electrons and muons are studied for completeness.
 
  • Data
    • data11_7TeV.periodD.physics_Egamma.PhysCont.DESD_SGLEL.repro09_v01/
    • data11_7TeV.periodG.physics_Egamma.PhysCont.DESD_SGLEL.repro09_v01/
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Software

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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.
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The Athena software releases to process data and MC are different since data is processed with an old release and MC has to be reprocessed with later TRT digitization versions.
 
  • for data
    asetup 17.2.5.2,AtlasProduction,here
  • for MC
    asetup 19.2.1.2,AtlasProduction,slc6,here
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Hopefully we can have another look at this when we have the Run 2 13TeV data and MC - using the same releases
 

Digitization

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
      postInclude.OverrideTRTparameters.py
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    • HT shaping is tabulated in '' and has to be hard-coded.
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    • 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.
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  1. High threshold ΔT0 shift

Tuning of high threshold shaping function

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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.
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The ASBDLR has separate discriminators for tracking (low threshold) and TR photon (high threshold). The high threshold discriminator has an additional shaping circuitry with a peaking time of 11ns to preserve signal uniformity. For the tuning it is seen that the HT signal has to be stretched to increase HT middle bit fraction as shown below. A new HT shaping function (HT shape 3) has slower falling time than original and a peak time also delayed about 1.5 ns.
  HTshape.png
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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.
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The Figure below shows the agreement for the HT middle bit fraction between data and MC as a function of HT ΔT0 shift for different TRT partitions. The HT middle bit fraction is always underestimated when using the original HT shape for all HT ΔT0 shifts. The HT shape 3 is sufficiently large to have a good data/MC agreement.
  tuningHTshape.png
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Tuning of high threshold value

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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 accordingly to restore original HT probability for each TRT partitions. Below table shows original high threshold values and new high threshold values to cope with new HT shape.
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The high threshold discriminator settings have to be tuned to restore the increased HT probability caused by the new HT shape; the increases in probabilities are 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 the figure below. High threshold values are raised accordingly to restore the original HT probability for each TRT partitions. The table below shows the original high threshold values and the new high threshold values to cope with new HT shape.
 
Original high threshold New high threshold
Barrel short 0.006047 0.006576
Barrel long 0.005477 0.006016
Endcap A-wheel 0.005916 0.006390
Endcap B-wheel 0.005680 0.006074
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Original high threshold New high threshold
Barrel short 0.006047 0.006576
Barrel long 0.005477 0.006016
Endcap A-wheel 0.005916 0.006390
Endcap B-wheel 0.005680 0.006074

tuningHLthreshold_HTprob.png

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Tuning of high threshold ΔT0 shift

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Since there is an additional shaping circuitry for high threshold, high threshold T0 setting can be differ from overall (or low threshold) T0 setting. Tuning of high threshold T0 setting is done by an additional T0 shift on top of overall T0 setting. The shift is applied after discrimination so that it has a discrete step of 0.78125 ns (See Andrew's slides for the detail). The implementation can be applied for each TRT partitions: Barrel short, Barrel long, Endcap A-wheel and Endcap B-wheel.
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Since there is an additional shaping circuitry for high threshold, high threshold T0 setting can be differ from the overall (or low threshold) T0 setting. Tuning of high threshold T0 setting is done by an additional T0 shift on top of overall T0 setting. The shift is applied after discrimination so that it has a discrete step of 0.78125 ns Discussion: 1. The step of 0.78125 ns exists before and after discrimination - I'd simply state that this is the step size. 2. Does it matter if the shift is applied before or after the call to DiscriminatorResponse() ? I guess not since it is the middle bit we are only interested in. (See Andrew's slides for the detail). The implementation can be applied for each TRT partitions: Barrel short, Barrel long, Endcap A-wheel and Endcap B-wheel.
 
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Following figure shows data and MC agreement of HT middle bit fraction as a function of HT ΔT0 shift. Different colors represent each TRT partitions, and empty squares have intersection point(s) with a red dashed line which means perfect data and MC agreement. Red arrows indicate possible HT ΔT0 shifts from original digitization setting. Barrel short is straightforward since it has only one point of intersection, but other three TRT partitions have two points of intersections. HT bit pattern distribution can be used to determine better HT ΔT0 shifts as shown below.
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The following figure shows data and MC agreement for the HT middle bit fraction as a function of HT ΔT0 shift. Different colors represent each TRT partitions, and empty squares have intersection point(s) with a red dashed line which means perfect data and MC agreement. Red arrows indicate possible HT ΔT0 shifts from original digitization setting. Barrel short is straightforward since it has only one point of intersection, but the other three TRT partitions have two points of intersections. The HT bit pattern distribution can be used to determine better HT ΔT0 shifts as shown below.
  tuningHTdeltaT0.png
 
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