STAR Offline FTPC QA Reference Histograms - Run 6

This document explains the FTPC Offline QA reference histograms for the Year 2006 data runs. For Year 2006, the EventQA histograms are divided into a set of general histograms and one or more multiplicity/trigger class histograms. In comparing the following page numbers and plots to what you have in the actual QA postscript files for your specific QA job, you may notice that things do not match page-by-page. The actual set of QA histograms generated during reconstruction depends on the set of Makers which are active in the chain. However, all plots in the EventQA files should be described here but may not appear on the specified page.

The histograms shown here are for the ppProduction run st_physics_7075188_raw_1030004. The postscript version of the Year 2006 QA reference histograms for this run is available in

Checking FTPC QA histograms with less than 400 pp events does not make much sense because of inconclusive statistics. For run 7075188, the "high tower histogram" set should be used. There are too few minbias events in this set to produce significant plots.

The offline QA histograms are used to monitor the functioning of the FTPC, its read-out electronics, the calibration corrections and the cluster and track finding parameters which are used in reconstruction. Please report significant changes to the FTPC mailing list: ftpc-hn@www.star.bnl.gov

Janet Seyboth, Max-Planck-Institute for Physics, Munich, Germany
March 2006

Page Index for FTPC QA Reference Histograms

General histograms:
  • Page 1
  • Page 2
    Multiplicity class histograms:
    Point histograms:
  • Page 1
  • Page 3
    Global track histograms:
  • Page 7
  • Page 12
  • Page 13
    Primary track histograms:
  • Page 14
  • Page 16
    Vertex histograms:
  • Page 18
  • Page 19

    General Histograms


  • Page 1

  • Ratio of total charge in all reconstructed clusters in FTPC East to West for low (solid line), mid (dashed line) and high (dotted line) multiplicity events. Should be peaked at ~1.

  • Page 2

  • The real chargestep corresponds to the maximum drift time in FTPC West (clusters from inner radius electrode) and is located near 170 timebins. This position will change slightly with atmospheric pressure. The hits beyond the step at timebin 170 are due to electronic noise and pileup. This step should always be visible even if it is only a "blip".

    The real chargestep corresponds to the maximum drift time in FTPC East (clusters from inner radius electrode) and is located near 170 timebins. This position will change slightly with atmospheric pressure. The hits beyond the step at timebin 170 are due to electronic noise and pileup. This step should always be visible even if it is only a "blip".

    The cluster radial position histogram for FTPC East(red) and FTPC West(blue) should show the radius step at the inner radius (~7.8 cm). If the temperature and pressure corrections applied to the FTPC drift maps are correct, the inflection point of the distribution of cluster radial positions will coincide with the black vertical line at 7.8 cm. Deviations of more than 1mm (2 bins) should be reported.

    Multiplicity Class Histograms


    Point Histograms

  • Page 1

  • Distribution of number of reconstructed space points in FTPC East (solid line) and West (dashed line). Should have similar means and widths; scales with centrality, depends on multiplicity cut for this set of plots (i.e. low, medium or high).

  • Page 3

  • Radial distribution of reconstructed space points in FTPC East. The distribution should be uniform except for the insensitive gaps between the readout sectors. Localized denser areas are due to noise. Ideally noisy pads are flagged in the FTPC gain tables so that they are not used for cluster finding. Less densely populated areas not on the sector boundaries are due to dead electronics. Empty areas not on the sector boundaries indicates a serious hardware problem. An FTPC expert should be contacted immediately if this is seen in fast offline-QA during data taking.

    Radial distribution of reconstructed space points in FTPC West. The distribution should be uniform except for the insensitive gaps between the readout sectors. Localized denser areas are due to noise. Ideally noisy pads are flagged in the FTPC gain tables so that they are not used for cluster finding. Less densely populated areas not on the sector boundaries are due to dead electronics. Empty areas not on the sector boundaries indicates a serious hardware problem. An FTPC expert should be contacted immediately if this is seen in fast offline-QA during data taking.

    Number of reconstructed space points assigned to tracks in FTPC East (solid line) and West (dashed line) in each padrow. The horizontal axis shows padrow numbers where FTPC-West is 1-10 and FTPC-East is 11-20. Padrows #1 and #11 are closest to the center of STAR. East and West should be similar in shape and magnitude. Spikes indicate noisy electronics; dips indicate dead electronics.

    Monitors the cluster quality in FTPC East. Ideally the clusters should have a pad length of 3-5 and a timebin length of 4-6. A prominent peak located at (2,2) indicates bad gas or loss of gain or electronic noise. An FTPC expert should check the analogous plots for points on tracks (St*QaGtrkPadTimeFtpcE/W). If the peak at (2,2) is not prominent in these plots, it was caused by noise.

    Monitors the cluster quality in FTPC West. Ideally the clusters should have a pad length of 3-5 and a timebin length of 4-6. A prominent peak located at (2,2) indicates bad gas or loss of gain or electronic noise. An FTPC expert should check the analogous plots for points on tracks (St*QaGtrkPadTimeFtpcE/W). If the peak at (2,2) is not prominent in these plots, it was caused by noise.

    Global Track Histograms

  • Page 7

  • Scatter plot of good global track multiplicities in FTPC West versus FTPC East. Distribution should be correlated and lie along the diagonal reference line. Magnitudes and widths depend on trigger condition and multiplicity cut for this set of plots (i.e. low, medium or high).

  • Page 12

  • Distribution of the number of fitted points on track for FTPC-East (solid line) and FTPC-West (dashed line) global tracks. Distributions should be similar within statistics and peak at 10. For year 2006 data, the peak at 6 is due to pileup.

    Azimuthal distributions for track direction angle (psi) for FTPC-East (solid line) and FTPC-West (dashed line) global tracks. These should be similar and flat within statistics except for dips at 30,90,150,210,270 and 330 degrees due to the hexagonal FTPC sector structure. Other holes indicate dead electronics. (Note that this plot is zero suppressed)

    Distributions of absolute value of pseudorapidity for FTPC-East (solid line) and FTPC-West (dashed line) global tracks. These should be similar within statistics and range from about 2.5 to 4.

    Transverse momentum (GeV/c) distributions for FTPC-East (solid line) and FTPC-West (dashed line) global tracks. These should be similar within statistics.

    Total momentum (GeV/c) distributions for FTPC-East (solid line) and FTPC-West (dashed line) global tracks. These should be similar within statistics.

  • Page 13

  • Impact parameter (in cm) from primary vertex for FTPC-East (solid line) and FTPC-West (dashed line) global tracks. These should be similar within statistics.

    Scatter plot of (x,y) coordinates for the first fitted space points on FTPC-East global tracks. The plot should be uniformly populated with hits; the FTPC hexagonal structure is visible.

    Scatter plot of (x,y) coordinates for the first fitted space points on FTPC-West global tracks. The plot should be uniformly populated with hits; the FTPC hexagonal structure is visible.

    Primary Track Histograms

  • Page 14

  • Mean transverse momentum distribution for FTPC-East (solid line) and FTPC-West (dashed line) primary tracks. These should be similar within statistics and peak between 0.2 - 0.4 GeV/c.

    Distribution of absolute value of mean pseudorapidity for FTPC-East (solid line) and FTPC-West (dashed line) primary tracks. These should be similar within statistics and peak around 3 - 3.5, provided that the event vertex distribution is centered at z=0.0.
    If the event vertex distribution (see StE..QaVtxPrz,pg 16 LL) is not centered at z=0.0, the |<eta/>| of the FTPC's is shifted in opposite directions. For example, when the average z position of the event vertices is less than zero (shifted east), the |<eta>| of FTPC East will decrease and the |<eta>| of FTPC West will increase.

  • Page 16

  • Distributions of absolute value of pseudorapidity for FTPC-East (solid line) and FTPC-West (dashed line) primary tracks. These should be similar within statistics and range from about 2.5 to 4.

    Transverse momentum (GeV/c) distributions for FTPC-East (solid line) and FTPC-West (dashed line) primary tracks. These should be similar within statistics.

    Vertex Histograms

  • Page 18

  • Difference between x,y position of primary vertex reconstructed from tracks in FTPC East and tracks from TPC. Ideally the distribution should peak at 0,0 Any significant deviation indicates a calibration problem and should be reported.

    Difference between z position of primary vertex reconstructed from tracks in FTPC East and tracks from TPC. Ideally the distribution should peak at 0. Any significant deviation indicates a calibration problem (t0 and/or temperature corrections) and should be reported.

    Difference between x,y position of primary vertex reconstructed from tracks in FTPC West and tracks from TPC. Ideally the distribution should peak at 0,0 Any significant deviation indicates a calibration problem and should be reported.

  • Page 19

  • Difference between z position of primary vertex reconstructed from tracks in FTPC West and tracks from TPC. Ideally the distribution should peak at 0. Any significant deviation indicates a calibration problem (t0 and/or temperature corrections) and should be reported.