Kaon_LT Experiment

                 Jan 8-9/26 PionLT/KaonLT Analysis Meeting Notes

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

                                (Notes by GH)

                    Today: PionLT will be discussed first

Thursday: Present

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

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

   Nermin Sadoun

CUA - Sameer Jain, Tanja Horn, Chi Kin Tam

FIU - Pete Markowitz

Junaid

------

Q2=3.85, W=2.02 analysis

- PID: should an Aerogel cut be used or not?

  - tried cuts >0, 0.5, 1.5, 3.0, 5.0 npe

    - low epsilon: no real difference in events away from pi+n MM peak

    - high epsilon: a bigger difference, looks like losting more events in peak

      than background though

  - conclusion: won't apply an Aerogel cut

  - *NB* W=2.62 data set had a >1.5 npe cut, Nathan should recheck if this is

    needed

- MM offsets and Diamond cut finalized

- working next on t-binning

Nathan

------

PionLT Lumi report

- finished tracking systematic uncertainties

  - plotted HMS, SHMS effs vs S1X rate

  - found mean & stddev of residuals from linear fit to get scale and random

    systematics

  - random syst: ~10-6 so can safely ignore

  - scale syst: ~0.1% HMS, ~0.2% SHMS

    - a one -sided uncertainty, means we might be over-estimating the tracking

      effs

    - *NB* Garth: looking more carefully at the scatter of the points in the

      plots, suggests to take the uncertainty as +/- anyways, there are more

      points below than above the linear fit, but the scatter of the points on

      both sides of the line (particularly around 300 kHz) is about the same

  - info added to Lumi report

- will send Lumi report to email list for comments, and eventually post on

  RedMine and Hall-C docDB

Nermin

------

PionLT LD2 analysis

- first step: reviewing Das' PID study for a single LD+, LD- setting from last

  year

  - his study was based on 4 runs of each SHMS polarity

- CoinTime plots: no offset is applied, will do so

- SHMS-CAL: will use <0.8 cut

- SHMS-NGC: will use <2.4 npe cut, particularly important for pi- settings

Next steps:

- will reply all LD2 data

- then do PID study, find detector efficiencies and estimate pi- purity

Sameer

------

KaonLT CoinTime blocking

- was using 3/4xELREAL for CoinRate

  - switched to 3/4x3/4, as suggested by Nathan

- needed to adjust time in Rate calculation for beam-off periods, as

  otherwise the rate is underestimated (sometimes significantly)

  - *NB* however this is not yet implemented for all Rate plots

- *NB* Nathan: the Q2=5.5 plot of CoinBlock vs Rate has some significant

  outliers that need investigation, likely something in the analysis failed

  that needs fixing

- should use EDTM-LT for Coin data, CPU*ELLT for Singles

Friday: Present

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

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

   Vijay Kumar, Nermin Sadoun

CUA - Chi Kin Tam, Tanja Horn, Sameer Jain

JMU - Gabriel Niculescu

CSULA - Konrad Aniol

Chi Kin

-------

KaonLT Q2=3.0, W=3.14 LT-sep

- investigated MM resolution discrepancy Data vs SIMC

  - plot ssdelta vs ssxpfp for SHMS center, low and high epsilon

  - plot x'tar vs MM

    - in both cases, looked for correlations, didn't find anything significant

  - also checked optics matrix element files

    - HMS: hms_recon_conf_opt2018

      - Junaid says this is the correct one

    - HMS: shms_newfit_xptar_april2020

  - studied MC resolution parameter sigma_res=3.5 to 4.5

    - 3.5 seemed best one for left-high epsilon setting

    - center-low epsilon: 4.0 seems better

    - center-high epsilon: tried 1.0 to 10.0

      - data is much wider than MC, but the effect is t-dependent

  - decision: will use modified resolution factor only for Lambda background

    subtraction, not for the MC yield calcs

- updated Lambda background fit procedure

  - when resolution is not a problem:

    - fit Gausian to both data and SIMC to find peak and apply MM offset

    - calculate separate chi-square for peak and sideband regions, and optimize

      chi-square separately for each region

    - seems to work, but needs some individual attention that everything is

      working correctly

  - when resolution is a problem

    - looks more objectively at the sideband regions and change fit by hand

- LT-sep results:

  - sigL shows a nice trend with t, but the 2nd t-bin is a bit low compared to

    3rd t-bin

    - looking at background subtraction to check

    - Data/MC ratios look fairly resonable at low, high epsilon, generally

      1.0+/-0.25 with some mild phi-oscillations

  - however, when adjusting background subtraction to move the 2nd t-bin to the

    1-3 bin trend, the 1st t-bin moves by ~50%(!)

    - *NB* this points to a large background subtraction systematic uncertainty

      that needs to be understood

  - Data vs MC kinematic comparison plots

    - some significant deviations noted, particularly for HMS-delta, yptar

- reran SIMC for all 5 settings

  - need to make sure diamond cut is correct

Alicia

------

- BSA press release

  - some discussion on modifications to the figures to be used

Vijay

-----

PionLT Low Q2 LT-sep

- reanalyzed unseparated cross sections with CoinTime cut width varied +/-10%,

  and computed the difference from the nominal cut:

  - low epsilon: 3.25%

  - mid epsilon: 1.4%

  - high epsion: 1.5%

  - Garth: suggests a scale syst unc of 1.5% for all data and an

    epsilon-dependent uncertainty of 1.8% that will affect primarily sigL (with

    delta-epsilon) magnification

Next Meetings

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

- we will continue with the current meeting schedule for now, can adjust once

  people better know their 2026 timetables

- Thurs: Jan 15 @ 16:00 Eastern/15:00 Regina

  - KaonLT will go first

- Fri: Jan  16 @ 11:00 Eastern/10:00 Regina

  - we will continue where we left off