Kaon_LT Experiment

                 Apr 24/25 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, Ivan Zhenchuk, Ali Usman, Alicia Postuma,

   Nathan Heinrich, Vijay Kumar, Nacer Hamdi

JLab - Dave Gaskell

FIU - Pete Markowitz

Virginia - Richard Trotta

Ohio - Julie Roche

Richard

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KaonLT both Q2=3.0 settings update

- W=2.32 setting

  - modified fitting algorithm, had some constraints on the fit range of some

    parameters, the ranges for some parameters were widened

  - it=10 shown

  - Data/MC ratios generaly better, particularly for lower 2 t-bins

  - higher 2 t-bins have weird Data/MC ratios near zero for phi~0 at high

    epsilon, where there's good data, Richard is investigating

  - L/T/LT/TT t-dependences look fairly reasonable

    - L>T everywhere

    - LT is still large, similar magnitude to L

    - TT~15, which is still large, but quite a bit smaller than last week

    - believes the differences are due to change in fitting parameters

    - *NB* Garth asks to next time please show "money plots", i.e. the plots of

      unseparated cross sections vs phi at both epsilon used to determine the

      separated cross sections

- *NB* some discussion about the fitting algorithm

    - Richard says he checks if the chi-square is stable after some iterations

    - Garth stresses the importance of also checking if the output parameters

      are close to the edge of a fitting window.  If they are, the chi-square

      will be stable, but the fit results not optimized

- W=3.14 setting

  - Data/MC ratios nicely between 0.75-1.25 for lowest t-bin

- *NB* SIMC might not yet have Ali's resolution correction, needs to confirm this

Next steps:

- finish W=2.32 setting

- reparameterize W=3.14 with new form

- parameterize Q2=2.115 and do first tests, should have this by next week

- planning full replay of Data and SIMC at end of May

  - Dave asks if a full replay is really necessary at this time

  - Richard points out it would be helpful to do before starting on

    systematics, as otherwise they would have to be redone later

  - Garth suggests to try replaying the "worst" setting and see if anything

    changes before deciding whether to replay everything else

Vijay

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PionLT Q2=0.425 MM offset study

- low epsilon, ~7 MeV shift between Data and MC, differences between peak

  positions are clearly evident before offset is applied

- mid epsilon, ~2 MeV shift

- high epsilon, ~4 MeV shift but not all SHMS settings done yet.  Some SIMC

  settings appear to have a normalization error

Next steps:

- will try calculating pion missed triggers correction using Alicia's G4 code

Ali

---

piDelta BSA analysis, new binning of 3 of 5 kinematic settings

- starting with Q2=3.0, W=2.32 "The worst setting"

  - hoping for 2 t-bins instead of 1

- low -t (0-0.6) center SHMS setting

  - fit of MCs to Data MM distribution generally looks good, except for a systematic

    discrepancy on left side of Delta peak

    - in comparison to the shown MM Data region (>1.0), the brown pi+n MC looks

      too low

    - however, the pi+n MC is actually fit to the top of the pi+n peak that is

      outside of this MM range, there is not sufficient freedom to raise the MC

      normalization to fully reproduce the data in the 1.0-1.1 MM region

    - the issue is that the resolution correction doesn't fully describe the

      pi+n tail

    - fortunately, the MM integration range for piDelta BSA excludes this poor

      fit region

- Alicia: how will the systematic uncertainty be calculated, will it take into

  account this discrepancy?

  - one systematic will be determined from the difference between data and MC

    shapes

  - another systematic will be determined by varying the background

    normalization within a "reasonable range", for the pi+n this should be

    based on the statistical variation at the top of the pi+n peak, and so will

    still not come all the way up to the data in the 1.0-1.1 MM region

- low -t right SHMS setting

  - good statistics and fits in all 8 phi-bins

- high -t left SHMS setting

  - 4 of 8 phi bins have good enough statistics and MM shapes to be fit

- high -t right SHMS setting

  - the other 4 phi bins have good data, so the sum of left and right gives

    good phi coverage

  - this setting has more statistical variation than the left

- high -t center SHMS setting still in progress

  - the issue is that at high -t, there is no pi+n tail between 1.0-1.1 GeV in

    some phi bins and Ali's MC fiting code breaks

  - shows plots at end of meeting, where Ali removed the pi+n MC from the fit

    - phi bins 4,5 do not have Delta MM shape and will not be included despite

      the fact that the code successfully gave a fit (i.e. fit is too uncertain

      to extract).  bins 1,8 are empty

Alicia

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BSA paper: No update yet from PLB

KaonLT u-channel study

- replayed all 10.6 GeV data with proton selected and beam helicity enabled

- interesting discovery re. background underneath omega peak

  - Henry Klest showed a PYTHIA simulation in the talk for his exclusive phi

    production proposal

    - gets a MM distribution similar to Alicia's data

    - Alicia got Henry's code working and will try passing PYTHIA events

      through SIMC

    - Ali has a bit of experience with Python for his MSc work with CMS

  - if that turns out to not work very well, the other option would be to

    modify one of the existing SIDIS generators in SIMC to handle proton

    fragmentation instead of pion fragmentation

    - Garth spoke to Bill about this.  They are planning to make such a

      generator, GH told that we would be very interested if they could make

      one soon rather than later

- RF PID studies

  - Q2=3.0, W=3.14 center SHMS setting

    - the RF works well for this setting, but it is not available for the right

      SHMS setting

    - RF vs Aerogel shows nice delineation between particle types

  - Q2=3.0, W=2.32 - RF is not good, a wide distribution

  - similarly RF not helpful for Q2=2.1 and 4.4 settings

  - Q2=5.5 - RF is helpful and there for all SHMS settings

- MM plots

  - Q2=3.0, W=3.14 helicity=+1

    - pi+n peak is heavily suppressed (~1000x) with PID cuts

  - Q2=3.0, W=2.32 - MM resolution is poorer, omega overlaps with pi+n peak so

    it might be difficult to extract u-channel results for this setting

  - Q2=2.1, W=2.95 - MM resolution is good, will have to apply pi/K sample

    subtraction since no RF info available

  - Q2=4.4 - same

  - Q2=5.5 - should have nice results despite lower statistics.  Can even

    separate eta-prime after pi+n suppressed with RF cuts

- Cherenkov plots

  - Q2=3.0, W=3.14 - HGC cut <2npe, Aerogel cut <3npe probably will change to

    <2npe

    - will evaluate a cut efficiency for the Aerogel, even if it is not

      strictly needed for BSA, the pi+n PRL referee asked for it so we should

      be prepared

  - Q2=3.0, W=2.32 - plots shown of aerogel with HGC cut and vice versa

- Planned analysis order of settings

  1) Q2=3.0, W=3.14: RF=Good Stats=High

  2) Q2=5.5, W=3.02: RF=Good Stats=Low

  3) Q2=2.1, W=2.95: RF=No   Stats=High

  4) Q2=4.4, W=2.74: RF=No   Stats=Low

  5) Q2=3.0, W=2.32: RF=No   Stats=Med

Nacer

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KaonLT Q2=0.5 LTsep setup

- now has Data and SIMC Yields per t-phi bin

  - wants to cross compare with Richard's results as a check

- working on scripts for Data-MC comparison plots and Ratios

- then will look at Richard's iteration scripts, with aim to simplify where

  possible

Junaid

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PionLT Q2=3.85, W=2.62 LTsep setup

- presents full equations for Normalized Yields and Error Calculations

  - very nice!  We appreciate the explicit documentation

- shows spreadsheet of Normalized Yield per t-phi bin

  - Dave: the errors seem too small

  - Note added later: JM found an error in his script, the errors were

    normalized twice by mistake

  - *NB* it would also be good to add columns of #Counts/bin and %error/bin

- working next on SIMC yields per t-phi bin

Nathan

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PionLT Coincidence Blocking studies

- met with Dave last Tuesday

- plots made of CTime.CoinTime_RAW_ROC1,2

  - ROC2 version has main CT distribution sitting on a very wide pedestal, from

    -600 to +600

  - ROC1 version has more structure, same pedestal to right of main CT

    distribution to +600, but a sloping decline to left of CT distribution

    extending to -400 and some sharp peaks at -400

  - Dave is mystified, assuming a 50ns coincidence time window, the full CT

    distribution should only be about 100ns wide, so what is causing the

    distribution to be ~1000 wide?

  - Dave: what timing window cuts are being applied?

    - Nathan says the timing cuts are 2000 bins winde, but isn't sure offhand

      what is the conversion to ns

  - NOTE: Nathan is using ROC1 version in the analysis

    - Dave suggests that the shoulder on the left of the ROC1 plot indicates we

      should use ROC2

      - plotting ROC1 vs ROC2 should indicate that it's running against a

        trigger window limit

- Dave will look at the Timing Cuts used on the files Nathan sent him, to see

  if he can figure out what's going on

- Nathan will try changing the TCOIN.param TDC cuts and see if it makes any

  difference

  - this would mean switching between offline and online versions

  - not expecting the deadtime effect in the Lumi study to go away, but even it

    changing would tell us a lot about the origin of the extra deadtime

Ivan

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- NSERC summer student starting with us next Thursday May 1

- we will have him look at BSA data for low Q2 KaonLT and PionLT settings

- Alicia has kindly offered to replay these data with helicity enabled

Next Meeting

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- Thur May 1 @ 15:30 Eastern/13:30 Regina

  - PionLT will go first

  ** THIS TIME WILL BE USED AT LEAST UNTIL THE END OF AUGUST **