GlueX PID Meeting, March 9, 2021

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Meeting time and day: 10:30 am, Tuesdays

Meeting Connections

  1. To join via a Web Browser, go to the page [1]
  2. To join via Polycom room system go to the IP Address: ( and enter the meeting ID: 927733173.
  3. To join via phone, use one of the following numbers and the Conference ID: 927733173.
    • US or Canada: +1 408 740 7256 or
    • US or Canada: +1 888 240 2560


  1. Announcements:
  2. Updates:
    1. Multivariate method
    2. CDC dE/dx
    3. PIDFOM
  3. PID systematics task force


  1. CDC dE/dx
    • Previously we had discussed how best to implement the space-charge corrections and decided that it would be best to do this in a layer between the REST production and the analysis trees. Naomi has been using it in her phi DSelector and sent the code to Alex A. Alex agreed to take a look at ReactionFilter.
    • Naomi's decision chart on which variety of dE/dx works best at any (p,theta) is near the end of CDC dE/dx space charge correction doc She pointed out that the pion/proton separation is good enough below 0.6 GeV/c that dE/dx from integral would be the better choice for tracks outside the 80-100 degree region of theta.
    • Curtis had suggested using both forms of dE/dx in the region surrounding each boundary and accepting the PID if it's a yes for either form, rather than using a sharp transition between the two forms at 80 and 100 degrees. For the phi this is not necessary, as the tracks are all forward of 80 degrees.
    • There is a gain mismatch between the corrected dE/dx from amplitude (~ 6% low), the monte carlo, and the corrected dE/dx from integral (~ 6% high), this appeared after the dE/dx truncation was reintroduced (the space-charge correction factors were obtained with untruncated dE/dx). Table 1 in the space charge correction doc gives some ratios, although comparison with MC would be more useful. It is not clear if a secondary correction factor is needed, or what it should be (the mismatch also varies with theta). Naomi will send her space-charge-correction DSelector to Nilanga so that he can compare new dE/dx with MC.