S&C Meeting, August 19, 2015 [Status of Hit Efficiency Studies]

  • Use standard track reconstruction with one layer of active Sti volumes excluded from tracking
  • Consider tracks with at least 40 TPC hits
  • In the skipped layer look for candidate hits within 5*sigma window in local Z and Y where sigma = track projection error (before the final track fit)

    In TPC layers we see either zero or one candidate hit in thus defined window

    There are some hits outside of 5*sigma window

    The chi^2 of candidate hits is consistent with the cut applied in Sti standard track reconstruction

  • The measured efficiency can be described using the following components

    P_measured = (P_instrumental + P_background) * P_corr * P_tracking


    P_instrumental (or P_detector) is essentially the probability for the detector active media to produce a signal that can be recorded (Includes efficiency of hardware and/or low level thresholds, pedestals, ...)

    P_background is the probability to have a hit within the window not produced by the considered track (Includes detector noise, other tracks, ...)

    P_corr include cluster/hit reconstruction efficiency, uncorrected unknown distortions, inefficiency of known corrected distortions

    P_tracking is the pure tracking efficiency, i.e. the probability to assign a hit to the track by the tracking algo.
    Includes algo specific requirements such as number of time hits can be used/reused, hit acceptance/rejection cuts (chi^2), ...

  • Currently I measure (P_instrumental + P_background) * P_corr essentially assuming P_tracking ~ 1
  • P_tracking can be measured directly by matching track/hits WITH and WITHOUT the skipped layer
  • Extra support plots

    How projected track position compares to the final track position with respect to the accepted hit?

    How projection error compares to the final track error?

  • http://www.star.bnl.gov/~smirnovd/stihify/

Padrow 1

Padrow 5

Padrow 10

Padrow 15

Padrow 20

Padrow 25

Padrow 30

Padrow 35

Padrow 40

Padrow 41

Padrow 42

Padrow 43

Padrow 44

Padrow 45