Kaon_LT Experiment

                 June 4-5/26 PionLT/KaonLT Analysis Meeting Notes

                 ------------------------------------------------

                               (Notes by GH)

                       This week: Gabriel will go first

Please remember to post your slides at:

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

Thursday: Present

-----------------

Regina - Garth Huber, Nathan Heinrich, Alicia Postuma, Dex Yadlowski,

   Vijay Kumar, Nermin Sadoun

Virginia - Richard Trotta

JMU - Gabriel Niculescu, Ioana Niculescu

Ohio - Julie Roche

CUA - Tanja Horn, Chi Kin Tam

Gabriel

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Bin Centering in KaonLT analysis

- goal is to determine Sigma0/Lambda and Lambda*/Lambda ratios for high

  epsilon, higher energy data, taking advantage of full statistics (no diamond

  cut applied)

- believe they understand the analysis workflow, looked at a variety of

  sources, including: Mohring, Volmer, Horn theses, Blok paper, V. Klimenko

  (Hall B 2024 thesis)

- Mohrning applies an explicit bin centering correction, however, to apply it

  here, would need to preserve all SIMC tries, not just successes

- looked more carefully at the Volmer+Blok MC Ratio Method that we use

  - justification of Ratio Method needs clarification

    - similar to Cauchy's Mean Value Theorem, which states there is a point

      where f(x-mean)=f-mean(x), but this point is not necessarily x-mean

    - one can argue that the relation is okay provided the bin size is

      sufficiently small

- did a pseudo-data study, generated MC data divided into 5 t-bins spanning

  5-95% coverage range, nearly equal statistics/bin

  - for each bin, find average Q2,W

  - calculate sigma-ave(Q2,W) vs sigma(Q2-ave, W-ave), find they differ by

    2-3%, giving a measure of the non-linearity of the cross section, clearly

    depends on the granularity of the bin

- looking at the convolution:

  f(x)_measured_distr=Int(a,b)[ g(y)_physics_distr * r(x,y)_det response]dy

  - going from g(y) to f(x) is straighforward, the backward transformation f(x)

    to g(y) is more complicated

  - tried various functions for g(y), e.g. Lorenzian+Gaussian kernel, and see

    if can recover g(y) from f(x) using the MC Ratio method

  - sees no problems at ~5% level, but random deviations between g_extracted

    and g_input with sigma~3%

- did only 1 iteration, would things be better if do more iterations?

  - tried g(y) with phi-distr+Gaussian kernel, fit

    g=a(1+b*cos(phi)+c*cos(2phi)) and do up to 20 iterations

  - find a strong correlation between a,c terms, fit did not converge with more

    iterations

- Julie: when doing this on data, one uses the experimental error bars and the

  improvement of chi-square vs iteration to prevent over-fitting, need to

  quantify whether the fit is "good enough"

  - if the cross section no longer changes, then it's good enough

  - also asks about the wrap-around from phi=-pi to phi=+pi in his analysis,

    where the data wrap-around, but the fit function has a rapid decline to

    zero at these points

- Tanja: agrees that the bin size is very important to the accuracy of the MC

  ratio procedure

  - It also depends on whether the cross section is changing rapidly (e.g. at

    the phi=-pi,+pi points in his study) while the exclusive reactions

    generally vary slowly with kinematics, the only real exception being pi+n

    sigL at -tmin and we need to take care to bin more finely there

  - inclusive studies are more susceptible to this, as it's much harder to

    identify experimental background leaking into the signal.  But in exclusive

    reactions the MM reconstruction is much cleaner in comparison

- Garth: the PionLT t-phi binning is not larger than Fpi-2 binning, the bin

  sizes between 12 GeV and 6 GeV data are about the same.  We paid attention to

  this when designing the experiment

- Vijay: did not find this problem of non-convergence in his LT-sep fitting

  - found that parameters did not change at all after a few iterations, both

  - the fit parameters and the experimental yields were stable, no need to keep

    iterating if nothing changes

- *NB* suggestion to Gabi was to incorporate the experimental errors in the

  procedure as per Julie's suggestion, as the pseudodata study seems to exhibit

  instabilities we do not see in practice with the data

  - other than this, no easy answers were offered

Friday: Present

---------------

Regina - Garth Huber, Alicia Postuma, Nathan Heinrich, Nacer Hamdi,

   Dex Yadlowski, Vijay Kumar, Nermin Sadoun

CUA - Chi Kin Tam, Tanja Horn

Virginia - Richard Trotta

Nathan

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Difficulties converting scripts for JLab new batch submission system, from SWIF

to SWIF2

SWIF: add-jsub Deprecation

The legacy add-jsub command has been deprecated and will be removed on June 15.

Please transition to the add-job command or the import features as soon as

possible.

Hanjie Liu:

If it's using the Auger job submission format, it needs to be modified to SWIF2

format.

https://jlab.servicenowservices.com/kb?id=kb_article_view&sysparm_article=KB0015611

Scientific Computing - SWIF - Scientific Workflow Indefatigable Factotum -

Knowledge Portal

Scientific Computing - Workflows - SWIF2 is the recommended tool for managing

groups of related compute jobs. It manages inputs and outputs

Brad's hands-on tutorial:

https://indico.jlab.org/event/1069/contributions/18589/attachments/14051/22727/Farm_Job_Examples-swif_slurm-May2026.pdf

Nathan's new scripts:

https://github.com/heinricn/UTIL_BATCH/blob/master/batch_scripts/run_batch_FullReplay_PionLT_newswif.sh

- no test batch queue is available, so progress is slow

- enountering EXIT_CODE=13, which indicates a permission issue, but no

  information is printed out to diagnose the problem

Richard's template for new system:

https://github.com/trottar/farm_template

Alicia's:

https://github.com/acpostuma/UTIL_BATCH/blob/LTSep_Analysis_2022/batch_scripts/run_batch_uchannel.sh

Alicia didn't immediately see a difference between this and Nathan's script but

this one ran.

- PionLT Q2=5.0 LT-sep

  - did 2 iterations, brought down high epsilon Data/MC ratios a lot, but not

    uniformly

  - fixed a 5 MeV error in P_HMS in SIMC input file

    - was due to Junaid's ad-hoc high momentum P_HMS offset, which was not

      removed although it should have been

- Q2=6.0

  - still missing some ROOT files, which requires job submission scripts to

    work first

Nermin

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PionLT LD2 Lumi studies

- last week: showed HMS scaler yields combined over all 6.4, 9.2 GeV runs gave

  boiling correction: (-3.75% +/- 0.19%)/100uA

  - SHMS was not consistent w/ HMS

- plotted normalized yield vs rate to see if the discrepancy was a rate issue

  - HMS rates up to 220kHz, with highest 220kHz point ~2% lower than linear

    trend

  - SHMS rates up to 1.25 MHz, non-linear dependence with over-correction at

    high rates

  - removed 1 HMS point and all SHMS points >200 kHz, then both spectrometers

    have similar trend, although deviations up to 3sigma are still seen

  - fit only <200kHz data:

    HMS      (-3.137 +/- 0.382%)/100uA

    SHMS     (-2.439 +/- 0.564%)/100uA

    Combined (-2.753 +/- 0.315%)/100uA

    Apply the combined slope to data: obtain a residual slope of

    (-0.273 +/- 0.683%)/100uA

  - Garth: red and black sets (one HMS, one SHMS) disgree by up to 3 sigma, so

    they're not consistent within statistical uncertainties, indicates an

    additional source of systematic error

    - Nermin: planning to add a systematic error to the -0.273%/100uA slope

      result using Nathan's standard-deviation method

- *NB* Nathan: should look also at the 6.4 GeV tracked/untracked data using

  EDTM instead of scaler with ELLT (single arm scans)

  - if the -2.753%/100uA slope is correct, then the 6.4 GeV tracked data shold

    be flat

  - Nermin: planning to compare TLT from EDTO to ELLT*CPULT for these scans

  - Garth: it's possible CPULT will have a problem, the real criterion will be

    to see what slope the tracked/untracked data give

Vijay

-----

Low Q2 PionLT systematic studies

- pi+ decay systematics

  - shows a plot of SIMC Decay_ON/Decay_OFF vs -t for mid-eps center setting

  - decay correction is 10%

  - trend vs -t looks small, but the SIMC statistical errors are large, running

    more SIMC statistics to see this better

  - Garth: the idea is to see of the decay fraction changes much across the

    acceptance, the pion decay fraction presumably depends on the spectrometer

    path length in the simulation, and the question is how sensitive we are to

    errors in that determination

    - if the dependence across the acceptance is small, one can argue the

      systematic uncertainty is small

    - if there is a 5% error in the correction, the systematic uncertainty for

      the data is 5%x10%correction=0.05%

  - Tanja seems generally happy with this approach, agrees the uncertainty

    appears to be <0.1%

- target thickness systematic

  - looked up Dave Meekins target geometry report (2018), and calculated the

    variation in the caliper measurements

  - obtained a variation of +/-0.027%

  - the same target stack was apparently used for KaonLT and PionLT, only a

    different cell in the stack

- EDTM TLT systematic

  - Nathan: the number he came up with was somewhat ad-hoc, probably reasonably

    correct also for Summer 2019 data

  - Vijay plans to look at TLT vs rate and determine the standard-deviation of

    TLT at a given rate

    - there are no CoinLumi studies in the Summer 2019 data to look at

    - *NB* Nathan agrees this is a sensible approach, however you need to be

      careful to have good beam current cuts to be sure you are comparing rates

      at as close as possible to the same rate

      - might have to make the current cuts tighter than usual for this study

- Tanja: asked whether these systematics are included in the draft paper that

  was circulated to the spokespersons

  - No, these are still in progress.  Garth will redo the model fits with the

    systematics after they are done.  The parameter central values will probably

    not change much, but the error bars will be more realistic

  - the circulated paper is to give the spokespersons a good idea of what the

    paper will look like, and to invite comments

Alicia

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u-channel

- mostly working on slides for Hall A/C (u-channel) and JLUO (BSA paper) talks

- has new Q_effective including Aerogel Knock-On Correction

  - recalculating yields and running a few iterations to get some plots for her

    talk

Nacer

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KaonLT Low Q2 systematic studies

- varying acceptance cuts, MM variation cuts, pi+n leakage normalization cuts

- MM variation cut was too large, took +/-5% of 1.08 GeV cut value, not the

  width of the cut, giving a 50 MeV varation, which is a large change to where

  in the MM histo the cut is applied

  - Garth suggested applying the % variation to the width of the cut instead

- similarly the pi+n leakage variation cut (to select normalization) of +/-5

  MeV seemed large

  - Vijay used 2 MeV cut variation in his MM cut study

Chi Kin

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KaonLT analysis issues

- HMS saturation correction

  - compared w/ Alicia's implementation:

    applied only to half of the focal plane

      if (hsxpfp>0) hsdelta += 3.0%&hsxpfp

  - applying this correction straightens the MM vs hsxpfp "banana", gives a

    reduction in Lambda peak sigma by ~5 MeV

  - also compared C0 parameter vs P_HMS

    - lots of scatter, hard to see trend

    - linear fit C0 = -0.393*P_cent + 1.018

- revisit pi+ leakthrough subtraction w/ improved MM resolution

  - showed a plot of pi+ leakthrough distribution, sees a small Lambda peak in

    pion dist, apparently the pi+ sample is not sufficiently clean

    - *NB* Richard: the pi+ selection cuts need to be tightened before

       subtracting from K+ data

  - will compare background subtraction results w/ Richard

- Heep offsets

  - Garth & Kin offsets somewhat different, but give simiar Heep replay result

  - replayed some physics data to see if MM shift is reduced

    however, used CKT individual beam energy fit offsets, not global offsets

    Q2=3.0 W=3.14:

    high epsilon MM shift is a bit smaller.  Was: 10 MeV.  Now: 6-7 MeV

    low epsilon ~2 MeV shift

  - *NB* Garth: suggests to try Garth and Kin's global offsets from 3 highest

    energies to physics data, instead of individual energy offsets

Richard

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KaonLT analysis

- replaying Q2=2.115 setting, ran into batch difficulties similar to Nathan

- switched to Q2=3.0 W=3.14 w/ new HGC-hole and Diamond cuts

  - big background, even at low epsilon (where RFtime cut is available)

  - HMS saturation correction won't make a big difference here due to P_HMS

  - the pi+n peak in K+ data is small, an empirical background fit is still

    probably needed

  - Garth: as Gabriel has noted earlier, there is no guarantee that the pi+

    leakthrough spectrum determined from PID cuts is exactly the same as the

    actual leakthrough in the K+ data

    - *NB* would it help to normalize the pi+Delta0 region instead of pi+n, in

      the cases where the pi+n peak is too small?

      - Richard will look into this

Next Meetings

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- Thurs: June 11 @ 13:00 Eastern/11:00 Regina

  - KaonLT will be first

- Fri: June 12 @ 12:00 Eastern/10:00 Regina

  - we will continue where we left off