Kaon_LT Experiment

                 Sept 5/24 PionLT/KaonLT Analysis Meeting Notes

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                                (Notes by GH)

                     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 - Garth Huber, Alicia Postuma, Muhammad Junaid, Nathan Heinrich,

   Ali Usman, Nacer Hamdi

Virginia - Richard Trotta

JLab - Dave Gaskell

CUA - Tanja Horn

Ohio - Julie Roche

CSULA - Konrad Aniol

Junaid

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PionLT Heep Coin Hodo-3/4 effs

- new plot of 3/4 effs vs SHMS momentum

  - planes 1,2,3 show a linear drop of eff with increasing momentum

  - plane 4 shows a low eff, but very large variation (50-75%) at P~2.4 GeV/c

  - GH: the drop off at low momentum is expected, but the linear drop at

    high momentum is puzzling

  - Dave: *NB* confident that there is an issue in the PID selection cuts used

    to calculate these efficiencies, that needs to be sorted out first, and

    then we can come back to this

-  finds the 3/4 effs are sensitive to the ptof_tolerance value

   - PionLT value=10, apparently set by C. Yero at start of PionLT run

     - changing to 15 results in slightly LARGER efficiencies

   - Ali: please recall the beta vs. cointime issue KaonLT encountered last

     year, this was because the tolerance variable was set wrong (was 100, it

     was supposed to be 2)

   - a value of 2 should be applied to ALL data

     - Junaid had tried this as well, results in even LOWER effs

More discussion about that to do about the 3/4 effs:

- Dave: NCER cut needs to be removed entirely, makes sense for negative

  polarity SHMS, but no sense at all for positive polarity

  - Junaid tried varying the CERCUT parameter, all the way down to zero

    (default is 2pe) and it made NO difference to the efficiencies

    - note Nathan did calibrate the NGC, so the pedestals should have a

      reasonable value when applying npe=0 cut that Junaid tried

  - Nathan thinks the CERCUT is legacy code that is not called, since for

    example no NGC was installed for KaonLT.  What did the code do then?

  - we spend some time looking at the code, it seems that the HGC is being

    called here instead of the NGC

    - however, protons also never Cherenkov in the HGC either, so this cut also

      should not be applied to Heep data effs

  - Dave suggests to remove this code completely from hcana and see what

    happens

  - Dave looks a bit more at the code, and sees that in THcHodoEff.cxx both

    Cherenkov and Calorimeter cuts are used

  - *NB* Junaid will investigate the code more thoroughly

Nathan

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PionLT Lumi studies

- new plots using Zach's code applied to 2021 data

  - SHMS Carbon 12143-12154

    - Scaler analysis shows a small linear rate dep

      - ElLT not yet applied

    - will look at fixing slopes on Carbon Scaler/NoTrack/Track analyses

- Mild antiboiling seen for LH2 12192-12198

  - Dave and Tanja expect Coin data are not as reliable for determining

    boiling corr than the 2022 dedicated singles runs

- One issue is what to use for TLT

  - right now, Nathan picks the higher TLT from either EDTM or CPU*ElLT

    methods

  - GH: *NB* this is "cherry picking", much better to decide which method is

    more reliable for a given run period, and then use it consistently for

    both Heep and physics data

Richard

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KaonLT Ratio debugging for Q2=4.4, W=2.74

- everything is looking pretty good, except that Ratios converge around 1/3

  instead of 1

  - ratios much flatter than before

  - comparisons of data and MC distribution shapes are reasonable

  - Richard reports that this factor is consistent across all settings, not

    just the Q2=4.4 shown today

  - GH and Tanja agree there seems to be a missing factor of ~pi somewhere in

    one section of the code that is consistent with the others.  When this is

    identified, things should look fairly good

- various studies to try to find the missing factor

  - reran SIMC from scratch instead of recalculating weights -- ratio unchanged

  - looking at histo binning in Exp Yield calc

  - also will check SIMC w/o recon_hcana

    - should change the distribution shapes, but not the normalization

  - Tanja suggested to run for only a small t range (~0.1) to check if it's a

    functional issue w/t-parameteriation

  - Nacer: try applying your code to Vijay's data and hunt for the difference

    between your plots and his

    - Vijay should be back and available for a meeting with Richard next week

Nacer

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KaonLT Heep studies

- proton absorption correction

  - reviewed John Matter's thesis and spreadsheet

    - they compared calculated and experimentally determined proton absorption

      results:

        A_pred=8.56% spreadsheet

        A_exp=9.03+/-0.07% by looking for missing protons other spectrometer in

	Heep singles data

- modified their table, removed NGC, need to adjust aerogel density for actual

  values used during KaonLT

  - 0.2 density should correspond to n=1.03 aerogel

  - Tanja: 1.015 density=0.08,  1.011 density=0.04

    all trays should have the same thickness aerogel.  The area will be

    different though

  - the correction factor ~7.5%, applying this factor changes the ratio from

    near 1.0 to ~1.08, except for 10.6GeV data where R=1.00 after factor

- tried different MM cuts to exclude pi0

  - ratios get a bit smaller for MM<0.10, 0.09, 0.08 cuts, but all above 1.0

    except 10.6GeV

- HMS matrix element check, hcana default vs old 6 GeV matrix

  - data vs MC shape difference gets a bit worse (8.2 GeV data)

  - ratios also get a few % worse, which is a bit surprising, only expected

    events to move around but not get lost

  - clearly the default matrix elements are better, this issue closed

More discussion about that to do about the ratios with absorption corr included:

- Ali: asks about the momentum dependence to the interaction length in

  spreadsheet

  - Matter's thesis: cross section indep of momentum >1 GeV/c

    - confirmed with their data for 4-10 GeV/c

    - our data are 2-8 GeV/c should be fine

  - Dave: the proton absorption correction is applied by other analyses, it is

    not optional as there are no proton absorption effects in SIMC

- Ali: there is a cut applied on aero tray in the replay, irrespective of

    whether an aero NPE cut is applied to the data

  - *NB* need to be 100% sure the same cut is applied also to SIMC

- GH: *NB* the MM distribution clearly has a much larger tail in data compared

  to MC, independent of the pi0 contamination.  This tail is ~5%, so seems to

  be the cause of the Ratio problem

  - Dave: *NB* please try looking at Emiss, W for Data & MC, not so used to

    looking at MM for Heep data, maybe it will show something

  - Dave: *NB* it is important to look at some Single Arm Heep to see if there

    are similar issues

    - GH agrees this is an excellent idea.  Since no protons are detected, no

      absorption corr is needed to be applied, so it will give important

      information

- *NB* GH's suspicion of what's wrong (added after meeting):

    - the spreadsheet assumes that interacting protons are completely lost and

      no trigger is made

    - if the protons scatter but still give a trigger, they end up in the

      Heep tail, and the spreadsheet correction is an over-estimate

    - if so, we would need to apply a much tigher MM cut to remove the

      interacting protons not included in the SIMC tail

      - hopefully the W and EM plots will shed light on what cut to apply

      - the Heep singles Data/MC ratios will also be critical to this

    - Henk came up with a modified method to evaluate the absorption

      correction, looking at the proportions of events in peak and tail, to

      accont for this

    - *NB* GH will review this info and see how to apply it here

Alicia

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Update from PRL:

- referee reports received Aug 12,14,31

- queries sent to 2 referees after receiving 3rd referee report, 1 response

  received so far

- we infer that one referee gives a report disagreeing with the other 2, and

  they have been asked to comment on it

Garth

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Hall C Winter Workshop  Jan 13-14/25

- at last meeting, discussed a session on "nearly final results" and what

  KaonLT might have ready by then

  - 3 talks seem likely:

    - Vijay, Richard, Ali

    - Richard and Vijay should coordinate e.g. on how best to show the various

      systematic studies

- Tanja: what about general experiment updates?

  - GH: this was not explicitly discussed.  Since there are starting to be lots

    of results nearing publication (unlike a few year ago), priority will be

    given first them.

    - once that part of the program is fleshed out, we will likely go back and

      ask for more general updates

 Next Meeting

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- Thur Sept 12 @ 16:30 Eastern/14:30 Regina

  - KaonLT will go first

  - *NB* Please note the new time and new Zoom ID!