Kaon_LT Experiment

                 Mar 14/24 PionLT/KaonLT Analysis Meeting Notes

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                                (Notes by GH)

                     Today: KaonLT 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, Nacer Hamdi, Ali Usman, Muhammad Junaid, Nathan Heinrich,

   Vijay Kumar, Alicia Postuma

CUA - Richard Trotta

York - Stephen Kay

CSULA - Konrad Aniol

JLab - Dave Gaskell

Ali

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MM shape study for DeltaPi BSA

- reran MC's with new resolution parameter

- starting on settings with lower P_HMS, where delta correction is not needed

- shows Q2=3.0, W=3.14, high stats setting, positive helicity

  - initial fit of MCs to data

  - new 10 MeV/bin instead of previous 4 MeV/bin (lower statistical errors/bin)

  - with new MM binning, it is now more clear that strength of DeltaPi peak is

    underestimated for some phi-bins

  - since SIDIS and rho bkds are so similar, using a fixed ratio of 90%

    SIDIS/10% rho for now

  - cyan=sum of bkds, pi+n tail+SIDIS+rho

  - optimistic that 2 t-bins can eventually be used for this setting (data

    shown is over full t-range)

- GH: since they are so similar, why don't you try fitting just one of rho or

  SIDIS to see which one is better, and just use that one?

  - DG: this would be an unphysical choice, but it probably makes no difference

    to your analysis

- Nacer: why are you fitting each phi bin separately?

  - we have confidence that SIMC can properly describe the shapes for the

    different processes, but not their amplitudes, so we need to fit each phi

    bin separately

Alicia

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MM cut study after resolution correction implemented in SIMC

- Dave suggested calculating Data/SIMC ratio for different MM cut values

  - UofR group meeting also suggested to compare w/ w/o HGC cut

    - HGC gets rid of KLambda leakthrough but not the shape of the region

      between pi+n and KLambda

  - ratios do not in general have a plateau vs MM cut

    - Q2=3, W=3.14 data shown

      - t-bins 1,2 show a decrease in ratio vs MM

      - t-bin 3 shows a plateau

      - t-bins 4-6 show an increase vs MM

    - behavior is similar for Q2=4.5, 5.5

- since the ratio is not flat, will instead try placing MM cut in region where

  expt yield is flat

  - Q2=5.5, flat region is MM=0.99-1.03, so will try MM cuts 1.01+/-0.02

  - Q2=4.4, Q2=3.0 W=3.14, flat region looks similar, so same MM cut

  - GH: can't think of anything better to try, given the situation

- Dave: have you looked at BSA vs MM cut?

  - a preliminary study was done last year, the final study will be done with

   these MM cuts

- Dave: if SIMC handles the radiative corrections properly, any cut below 2pi

  threshold should give the same answer

  - GH: not sure about this, the pion scattering in the collimator also

    populates this region, in Fpi-1,2 we had to use a cut well below 2pi

    threshold to avoid being too sensitive to this region

- Dave: there is no SHMS collimator routine in SIMC

  - GH: wasn't aware of no routine was included at all.

    *TASK for GH:* find the HMS collimator code used in Fpi-2 analysis, and get

    instructions on how to modify it for SHMS collimator geometry

- Nacer: can an RF cut be applied to help clean up this MM region?

  - no, only a small subset of 10.6 GeV data has the RF information available,

    unfortunately

HMS Delta-correction

- P_HMS=6.59, Q2=3, W=2.32 data

  - hcana uncorrected MMpi vs hsxpfp shows line with tilt on top half

  - using reconstructed MMpi script to determine correction

    - applying if hsxpfp>0: hsdelta+=3.0*hsxpfp

  - resulting MM distribution is narrowed

- P_HMS=5.292, Q2=2.1, W=2.95 data

  - hcana uncorrected MMpi vs hsxpfp shows line with tilt on bottom half

  - correction: if hsxpfp<0: hsdelta-=4.0*hsxpfp

- having difficulty implementing this correction in hcana

  - recompiling hcana on iFarm gives complaint about missing PODD variables

  - Stephen: please *send* the PODD error and he will look at his notes to see

    if he can fix

  - Nathan: thinks it might be better to implement correction in the kinematics

    file

CKY Regge model

- received LT' predictions from BG Yu for the BSA paper

Richard

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Subtracting pion leakthrough

- last week's results had HGC hole cut inverted, taking only events in the hole

- now the pi+ dist comes all the way across the MM acceptance

- Q2=2.1 setting, high epsilon

  - pi+ subtraction does not clean up region left of KLambda peak

  - planning to re-optimize PID cuts after graduation

Unsep and Separated Q2=3.0, W=2.32 xsect

- shows ratios vs phi,t at high, low epsilon

  - looking at what's responsible for Data/SIMC ratios being much larger at

    high eps than low eps

  - trying various initial values of model parameters

    sigL=g(W)*(p1+p2*logQ2)exp(p3+p4*logQ2)*(-t+0.2) 

    -- changed last part to just -t to get better t-dependence

    sigT=g(W)*p5/(1+p6*Q2)

  - Dave: maybe remove the Q2-dependence and only have a simple t-dependence

- Dave: the *real issue*, however, is that if you have sigL<0 from the

  beginning, there's a problem with the data itself, not the iteration

  - GH: exactly what MM region is integrated for these yields?

  - MM cut is applied after pi-subtraction

    - GH: if we can't clean up the region left of KLambda with cuts or pion

      subtraction, then we will have to consider fitting a polynomial and

      subtracting it

    - Dave: yes, we will need to sort this out

- Richard shows MM plots for same setting at high and low epsilon

  - RF cut can be used only at low epsilon, region left of KLambda is

    noticeably cleaner than high epsilon

  - GH notices that pion subtraction peak is much narrower than the pi+n MM

    leakthrough peak

  - Ali's pion sample was analyzed as if pions, not K, hence the peak is narrow

    - normalizing to the height of the pi+n peak will result in too little pion

      leakthrough being subtracted, as the integrals won't match

  - *Ali* will give Richard his cuts and RT will make a branch of his analysis

    for the pion subtraction

Vijay

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PionLT low Q2 lt-analysis

- found bug in script, error bars vs phi now more reasonable

- shows results after 1 iteration for Q2=0.38, all 3 epsilons

  - some discussion about phi-dependence of lowest t-bin

  - the low epsilon setting seems to have a different phi-dependence than mid

    and high eps, which is weird

    - Dave: this could indicate a residual offset issue, lowest t-bin is always

      more sensitive to the offsets

    - Vijay will investigate further

  - t-bins 2-7 have more consistent phi-dependence at low, mid, high epsilon

  - 8th t-bin has poor statistics, might have to be removed from analysis

- shows separated cross sections after 1st iteration, and model fits for

  iteration #2

  - t-bins 1,8 look like outliers for sigT,L after iteration #1

  - if only t-bins 2-7 included in fit, things are more consistent

  - will have to see what this looks like after more study

Nacer

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KaonLT low Q2 event selection

- won't show any plots, since the meeting is getting long

- tweaking some cuts, changing the RF windows

  - RF cut is very effective, needs fine tuning

  - GH: since the RF cut is so effective, you can probably get by with a

    combination of slightly looser PID cuts, to avoid cut-dependence to the

    result

Nathan

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Setting up PionLT Luminosity analysis

- in contact with Dave Mack regarding BCM calibrations

  - DM did our first calibs from 2021 run, NH will follow up with him on run#'s

  - Dave: if you can generate ROOT trees for him to analyze, it would be even

    better

Weird hcana issue

- hcana suddenly did not know what replay variables were

  - spent a day debugging

  - restored things, but no idea what happened, as could not find any

    difference from how things were set up before

Going through Richard's python scripts and finding what's missing

- will plan on meeting RT in early April, after his defense

Junaid

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Setting up PionLT Heep study

- had some issues with lt-sep package

- merged cut files for 2021,22

- added ngcer

- updated RF time offsets

PID cuts

- HMS cal-etot-track-norm>0.7

- HMS cer NPE>1.5

- CoinTime, extremely clean, practically no randoms

  - should be able to just place a cut around prompt peak, no random

    subtraction

Next Meeting

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- Thur Mar 21 @ 15:00 Eastern/13:00 Regina

  - PionLT will go first