Difference between revisions of "Meeting-3-8-2018"

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(Current analysis/issues)
 
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# Current analysis/issues:
 
# Current analysis/issues:
#*  
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#* [https://halldweb.jlab.org/wiki-private/images/1/18/CDC_Mar7.pdf CDC]
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#*[http://www.jlab.org/Hall-D/detector/fdc/reports/DC_mar8_2018.pptx CDC events again]
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#*
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# fADC125
 
# fADC125
 
# Other
 
# Other
 
 
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= Minutes =
 
= Minutes =
  
Participants: Naomi (CMU) Eugene, Beni, Alex B., Simon, Sergey, Alex A., and Lubomir (JLab).
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Participants: Naomi (CMU) Eugene, Beni, Alex B., Simon, Alex A., Thomas, and Lubomir (JLab).
 
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= Discussions about the current run  =
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== CDC thresholds ==
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- Naomi proposed several options: setting the CDC thresholds from the widths of the pedestal, scaling the current thresholds, or doing dedicated threshold scan with 4 different thresholds same for all straws.
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After lengthy discussions that included all kind of topics, we agreed that it is worth doing the threshold scan but after we figure out what is going on with the CDC gas leakage. Initially, the observable to be optimized was signal/noise as taken from the amplitude spectrum (if you can fit the noise and the signal reliably). At the end of the discussion we concluded that it is better to have enough statistics to get the rho yields (like 10M triggers per setting).  Sergey pointed out that we should not really be calling the initial "noise" peak "noise".  With the cosmics runs we see a real noise peak from the electronics - the earlier threshold scan would have set the thresholds to make this noise level acceptable.  What we are seeing now is (presumably non-hadronic) background.    Later addition from Naomi: it would be best to do the threshold scan when the atmospheric pressure is stable, so that the changing gain does not confuse the analysis.
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- Beni: excluding the hits with times before the expected signal may improve the tracking (the wire-based one) and then the effect of the threshold may not be so important. Simon will re-analyze the two runs that Justin used to compare the rho yields with different thresholds, using a more appropriate software time window on the CDCdigihits.
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=  Current analysis/issues  =
  
== CDC gas issues ==
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- Naomi analyzed the runs from the CDC threshold scan (presentation attached). The number of hits certainly depends on the threshold, mostly pronounced between 90 and 110 (f125 units). The percentage of hits that participate in the tracks (about 30% ) also goes down with the threshold, however this change is relatively small in the 90-140 threshold range.
  
- Naomi showed amplitude spectra for different regions of the drift time spectrum and compare them for runs in December and now. Her conclusion is that we are losing some charge, possible due to oxygen contamination in the gas as Beni suggested this morning. On Monday during the access Lubomir will measure the O2 contamination. We will also sniff around the CDC. If needed we may increase the flow and re-measure the O2.
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- The interesting feature Naomi found is that there's a class of events with low amplitudes with a peak in time that is 20ns later than the peak in the drift time for the good hits. Some of these hits end up as part of the tracks, especially at low thresholds, and their theta/z distributions look similar to the ones of the good hits. We had long discussions about the origin of these hits without any conclusion: cross-talk, some kind of e.m.background, electronic noise, reflection at the open end of the straw ... Important is to look at the wave forms of these events (Eugene). Pure electronic noise we can study on the channels that are disconnected from the straws. To study the electronic noise we are also going to take data with the pulser (random trigger).  
  
- Lubomir showed the average charge vs drift time for the FDC that is indicative of electron losses due to electronegative contamination. The relatively small slope was always there and is related to the way the charges are collected by the electronics, also because only one peak is readout. Important is to compare such plot for the CDC for runs in December and now.
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- Lubomir measured the Oxygen contamination in the CDC with the two sensors both showing very small values, however the sensors need calibration. Also the sniffer showed some higher levels of Ar/CO2 at the sides of the magnet. At the end most likely the sniffer was damaged by the magnetic field so Beni could not use it today.  
  
= fADC125 =
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- Lubomir showed some CDC events from the raw mode run, that were shown before by Sergey, just adding info about the drift time in the x/y plots (attached).
  
- Cody is working on implementing multi-peak mode. The way it works now, without comparing to the threshold, is not very useful. Naomi: only the first peak is calculated precisely.  We will still have to be very careful with the thresholds.  Lubomir: Still, having second is better than nothing. Eugene; the best is to use raw mode and evaluate all these effects. It should be done with the nominal high current even with a dead time close to 100%. We plan to have such run with ~10M trigger.
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- Not directly related to the tracking: we discussed the 30 J/psi events that are missing in the newest analysis; Thomas finds also 20-50% reduction of the phi's in v7 (and v11) of the the 2016 data analysis, compared to v6. Alex is going to relax the cuts to try to reconcile v6 and v7.
  
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- We were kicked out of the room by the next gluex meeting.

Latest revision as of 11:02, 9 March 2018

March 8, 2018 Drift Chamber meeting

Connection

  1. Instructions for Bluejeans meeting connection
  2. Meeting ID: 290664653

Headline text

  1. To join via a Web Browser, go to the page [1] https://bluejeans.com/290664653.

Agenda

  1. Current analysis/issues:
  2. fADC125
  3. Other

Minutes

Participants: Naomi (CMU) Eugene, Beni, Alex B., Simon, Alex A., Thomas, and Lubomir (JLab).

Current analysis/issues

- Naomi analyzed the runs from the CDC threshold scan (presentation attached). The number of hits certainly depends on the threshold, mostly pronounced between 90 and 110 (f125 units). The percentage of hits that participate in the tracks (about 30% ) also goes down with the threshold, however this change is relatively small in the 90-140 threshold range.

- The interesting feature Naomi found is that there's a class of events with low amplitudes with a peak in time that is 20ns later than the peak in the drift time for the good hits. Some of these hits end up as part of the tracks, especially at low thresholds, and their theta/z distributions look similar to the ones of the good hits. We had long discussions about the origin of these hits without any conclusion: cross-talk, some kind of e.m.background, electronic noise, reflection at the open end of the straw ... Important is to look at the wave forms of these events (Eugene). Pure electronic noise we can study on the channels that are disconnected from the straws. To study the electronic noise we are also going to take data with the pulser (random trigger).

- Lubomir measured the Oxygen contamination in the CDC with the two sensors both showing very small values, however the sensors need calibration. Also the sniffer showed some higher levels of Ar/CO2 at the sides of the magnet. At the end most likely the sniffer was damaged by the magnetic field so Beni could not use it today.

- Lubomir showed some CDC events from the raw mode run, that were shown before by Sergey, just adding info about the drift time in the x/y plots (attached).

- Not directly related to the tracking: we discussed the 30 J/psi events that are missing in the newest analysis; Thomas finds also 20-50% reduction of the phi's in v7 (and v11) of the the 2016 data analysis, compared to v6. Alex is going to relax the cuts to try to reconcile v6 and v7.

- We were kicked out of the room by the next gluex meeting.