Kaon_LT Experiment

                Sept 26/23 PionLT/KaonLT Analysis Meeting Notes

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                              (Notes by GH & AH)

                     Today: PionLT will be discussed first

Please remember to post your slides at:

https://redmine.jlab.org/projects/kltexp/wiki/Kaon_LT_Meetings

Present

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Regina - Nathan Heinrich, Garth Huber, Vijay Kumar, Nacer Hamdi, Muhammad

   Junaid, Alicia Postuma

CUA - Richard Trotta, Tanja Horn

FIU - Pete Markowitz

Nathan

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Hodoscope calibrations

- time walk work took longer than expected, is finally done

- time walk correction for the hodoscope calibration, using the formula

  (from Carlos's documentation) to fit the time difference between TDC and fADC.

- correction is of the form:

  f_TW = 1/[ (a/t_thr)^c2 - (200/t_thr)^c2 ]

  where the second term is apparently used instead of c1

- some outliers w/small errors are due to bad fits, so they were removed from

  correction

- all paddle data are divided into two periods, Winter 2021-22, Summer 2022

  - some paddles have very clear divisions in the offset

- previous work (last week) missed c1, now it's included

  - had to do some code fixes to get everything working

- now moving to second part of calibration, Vprop

  - wil be asking Junaid for help in seeing how often Vprop needs to be redone

  - will push new offset params and code to GitHub tomorrow

Junaid

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- Still waiting on Nathan to push hodoscope calibration into the working

  software, will help him on calibs starting tomorrow

- Next will be re-check calibration of the drift chamber, using new hodo calib

Richard

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Heep offsets

- replay of data with new offsets to see if they worked

- was running wrong branch, now re-running data with correct branch

LT-sep preliminaries

- issues with t-phi binning

  - getting zeros in certain bins, some histos had wrong ranges, now fixed

  - has a code to automatically equalize statistics between t-bins for low

    epsilon, using center+left settings

    - the code had some issues, for example was using a modulus and this gave

      some weird results, now fixed

- worked on LTsep t-average calculation in parameterization

- discussion about Data/MC ratios at Q2=2.1

  - low epsilon ratios look reasonable before iterations, in the vicinity of 1

  - high epsilon ratios have much larger range, possible bug that needs to be

    fixed

    - using 8 phi-bins, 3 t-bins

    - phi-bin #5 has very high Data/MC ratio (near 1000)

      - GH wonders if maybe one SHMS setting is missed in forming the ratio?

- still some bugs in weight calibration script that need to be fixed

  - running the script causes unexpected changes to the weight

ViJay

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Heep offsets

- started running Heep Coin SIMC Low Q2 data, to allow for in-plane offsets

  extraction

Hodo efficiency calc

- DG suggested adding an extra PID cut to be sure effs near 97% are not due to

  proton contamination

  - looked at code with Nathan, it's in hcana, not the report files

  - this is because it needs to make use of tracking info to select the right

    paddle and not all of this information is available in the report files

  - the code looked confusing, not sure how to implement a better PID cut

  - GH will see if DG, NH, VK are available for a separate meeting on the

    necessary code change

Next steps: elastic cross section measurements

Alicia

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BSA cointime studies

- cointime with PID cut, Q2=3, W=3.14 data

- investigating the reason of asymmetry in the CT distribution

  - i.e. the accidental peaks are not flat near the prompt peak, but have a

    plateau about 30ns wide which are higher and the valleys between the peaks

    are more filled in

- tight missing mass cut around neutron mass leads to more asymmetry

- coincidence time vs. missing mass shows prompt and accidental bands

  - a large band at the neutron mass extending well into accidental events is

    also seen!

  - it is clear this band is the reason for the asymmetry in the CT plot

  - Even with accidentals happening at different times, the tracks are still well

    reconstructed and that corresponds to neutron mass

    - this means we have real e+pi coincidences corresponding to neutron MM

      (info coming from tracking algorithm), but for some reason the CT time is

      wrong up to 10-20 ns!

    - GH speculates this is due to the bad CT resolution in these 10.6 GeV data

      and the loose trigger timing that was used in this beginning KaonLT run

      - the CT problem was fixed mid-way through the KaonLT data, so Alicia

        will have to be careful to treat data before and after this correction

        differently

    - GH: assuming these are real good e+pi coincidences, as indicated by the

      MM peak corresponding to neutron mass, even though CT time is bad, we

      will need to apply a correction for the data lost by the tight CT cut

      - this should not affect the BSA data, but for sure the correction is

        needed for the L/T-sep data ***Richard and Ali take note!***

    - for accidental subtraction, use bands far away from the prompt peak

    - to correct for good e+pi+n events removed by tight CT cut, need to take

      difference between random peaks close and far from the prompt peak

    - TH: Richard should do a cut study to see the effect in the K+ data

       - AP: it would be good if K+ and pi+ corrections are similar within

         errors, and if so, apply the pi+ correction to K+ data as the

         uncertainties would be smaller

Nacer

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- still going through Carlos Yero's thesis and Hall C papers from GH

- looking to start looking at 3.8GeV KaonLT data soon

Next Meeting

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- Tues Oct 3 @ 15:00 Eastern/13:00 Regina/12:00 Pacific

- KaonLT will go first

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