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Kaon LT Meetings » mtg_23sep26.txt

Garth Huber, 09/26/2023 05:33 PM

 
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                Sept 26/23 PionLT/KaonLT Analysis Meeting Notes
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                 -----------------------------------------------
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                              (Notes by GH & AH)
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                     Today: PionLT will be discussed first
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Please remember to post your slides at:
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https://redmine.jlab.org/projects/kltexp/wiki/Kaon_LT_Meetings
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Present
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-------
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Regina - Nathan Heinrich, Garth Huber, Vijay Kumar, Nacer Hamdi, Muhammad
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   Junaid, Alicia Postuma
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CUA - Richard Trotta, Tanja Horn
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FIU - Pete Markowitz
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Nathan
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------
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Hodoscope calibrations
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- time walk work took longer than expected, is finally done
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- time walk correction for the hodoscope calibration, using the formula
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  (from Carlos's documentation) to fit the time difference between TDC and fADC.
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- correction is of the form:
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  f_TW = 1/[ (a/t_thr)^c2 - (200/t_thr)^c2 ]
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  where the second term is apparently used instead of c1
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- some outliers w/small errors are due to bad fits, so they were removed from
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  correction
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- all paddle data are divided into two periods, Winter 2021-22, Summer 2022
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  - some paddles have very clear divisions in the offset
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- previous work (last week) missed c1, now it's included
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  - had to do some code fixes to get everything working
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- now moving to second part of calibration, Vprop
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  - wil be asking Junaid for help in seeing how often Vprop needs to be redone
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  - will push new offset params and code to GitHub tomorrow
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Junaid
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------
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- Still waiting on Nathan to push hodoscope calibration into the working
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  software, will help him on calibs starting tomorrow
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- Next will be re-check calibration of the drift chamber, using new hodo calib
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Richard
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-------
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Heep offsets
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- replay of data with new offsets to see if they worked
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- was running wrong branch, now re-running data with correct branch
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LT-sep preliminaries
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- issues with t-phi binning
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  - getting zeros in certain bins, some histos had wrong ranges, now fixed
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  - has a code to automatically equalize statistics between t-bins for low
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    epsilon, using center+left settings
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    - the code had some issues, for example was using a modulus and this gave
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      some weird results, now fixed
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- worked on LTsep t-average calculation in parameterization
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- discussion about Data/MC ratios at Q2=2.1
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  - low epsilon ratios look reasonable before iterations, in the vicinity of 1
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  - high epsilon ratios have much larger range, possible bug that needs to be
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    fixed
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    - using 8 phi-bins, 3 t-bins
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    - phi-bin #5 has very high Data/MC ratio (near 1000)
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      - GH wonders if maybe one SHMS setting is missed in forming the ratio?
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- still some bugs in weight calibration script that need to be fixed
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  - running the script causes unexpected changes to the weight
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ViJay
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-----
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Heep offsets
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- started running Heep Coin SIMC Low Q2 data, to allow for in-plane offsets
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  extraction
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Hodo efficiency calc
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- DG suggested adding an extra PID cut to be sure effs near 97% are not due to
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  proton contamination
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  - looked at code with Nathan, it's in hcana, not the report files
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  - this is because it needs to make use of tracking info to select the right
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    paddle and not all of this information is available in the report files
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  - the code looked confusing, not sure how to implement a better PID cut
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  - GH will see if DG, NH, VK are available for a separate meeting on the
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    necessary code change
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Next steps: elastic cross section measurements
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Alicia
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------
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BSA cointime studies
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- cointime with PID cut, Q2=3, W=3.14 data
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- investigating the reason of asymmetry in the CT distribution
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  - i.e. the accidental peaks are not flat near the prompt peak, but have a
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    plateau about 30ns wide which are higher and the valleys between the peaks
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    are more filled in
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- tight missing mass cut around neutron mass leads to more asymmetry
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- coincidence time vs. missing mass shows prompt and accidental bands
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  - a large band at the neutron mass extending well into accidental events is
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    also seen!
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  - it is clear this band is the reason for the asymmetry in the CT plot
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  - Even with accidentals happening at different times, the tracks are still well
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    reconstructed and that corresponds to neutron mass
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    - this means we have real e+pi coincidences corresponding to neutron MM
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      (info coming from tracking algorithm), but for some reason the CT time is
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      wrong up to 10-20 ns!
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    - GH speculates this is due to the bad CT resolution in these 10.6 GeV data
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      and the loose trigger timing that was used in this beginning KaonLT run
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      - the CT problem was fixed mid-way through the KaonLT data, so Alicia
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        will have to be careful to treat data before and after this correction
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        differently
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    - GH: assuming these are real good e+pi coincidences, as indicated by the
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      MM peak corresponding to neutron mass, even though CT time is bad, we
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      will need to apply a correction for the data lost by the tight CT cut
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      - this should not affect the BSA data, but for sure the correction is
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        needed for the L/T-sep data ***Richard and Ali take note!***
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    - for accidental subtraction, use bands far away from the prompt peak
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    - to correct for good e+pi+n events removed by tight CT cut, need to take
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      difference between random peaks close and far from the prompt peak
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    - TH: Richard should do a cut study to see the effect in the K+ data
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       - AP: it would be good if K+ and pi+ corrections are similar within
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         errors, and if so, apply the pi+ correction to K+ data as the
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         uncertainties would be smaller
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Nacer
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-----
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- still going through Carlos Yero's thesis and Hall C papers from GH
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- looking to start looking at 3.8GeV KaonLT data soon
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Next Meeting
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------------
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- Tues Oct 3 @ 15:00 Eastern/13:00 Regina/12:00 Pacific
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- KaonLT will go first
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Join Zoom Meeting
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https://uregina-ca.zoom.us/j/94470211297?pwd=djBROEdWUENLUTF3ZFN1c0kvS0VIQT09
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Meeting ID: 944 7021 1297
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Passcode: 320362
(294-294/412)