Kaon_LT Experiment

                 Mar  7/24 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, Nathan Heinrich, Muhammad Junaid, Nacer Hamdi, 

   Alicia Postuma, Ali Usman, Vijay Kumar

FIU - Pete Markowitz

CSULA - Konrad Aniol

CUA - Richard Trotta, Casey Morean, Tanja Horn

JLab - Dave Gaskell

Nathan

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PID plots for SHMS NIM paper

- HGC efficiency was found to be low, ~80%

  - removed zero bin entries as Vijay had found in his PID study, then ~99%

    outside of hole region

  - indicates this is still a problem during PionLT data taking

    - DG: are you sure these aren't otherwise bad events?

    - GH: Vijay had shown that bad HGC events corresponded to good MMK, not due

      to other expt backgrouns

  - believed to be due to either a bad reference time or bad pedestal caused by

    high rates per PMT due to low HGC granularity (only 4 channels covering

    focal plane)

  - will eventually need to use fADC mode-10 data to determine an apporpriate

    correction

  - *IMPORTANT NOTE* Richard uses HGC NPE<1.5 cut, so maybe a correction is not

    needed for his data, but he will have to confirm, for example if a good HGC

    time is required to calculate the NPE, then a correction would still be

    needed

- shows efficiency plots vs X,Y and vs delta for Aerogel, NGC, HGC

- shows NPE correlations between detectors for PID

Next steps:

- will look through Lumi scripts and try to understand recent changes

Junaid

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DC efficiency plots for SHMS NIM paper

- removed outliers

- finalizing calorimeter plots for paper

Next steps:

- setting up scripts for Heep COIN data analysis

Richard

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Fixes to xsect uncertainty calcs

- met w/GH on Monday afternoon and found the problem

- errors were not propagated correctly

- uncertainties now stable vs iteration

Pion contamination subtraction

- Ali provided clean pi+ samples for Q2=2.115 and both Q2=3.0 settings

- a sample subtraction is shown

  - pi+ subtraction is red curve, stops at MM=1.24 for some reason

  - DeltaPi contribution seems surprisingly small

  - some rechecks should be done

Xsect comparo w/ and w/o pion subtraction

- Q2=3.0, W=3.14 shows ~20-25% reduction in sigL at low -t, no MM cut applied

  - makes sense that low -t region is most affected, as pi+ cross section

    should have much steeper t-depenence than K+

- comparison with 1.10<MM<1.18 cut applied

  - about 50% reduction in lowest -t bin, less in other bins

Continuing separated Xsect issues

- Q2=3.0, W=2.32 still shows epsLO>epsHi yields

  - sigL works out negative, sigT unrealistically small

- Q2=2.115, sigL consistent w/zero for lowest -t bin

- compare to Marco's K+ data for Q2=3.0, W=2.32

  - his epsLO value is close to our epsHI value

- having difficulty getting things to converge sensibly for different

  iterations

- Vijay: what do your Ratio plots look like?

  - RT shows Q2=3.0, W=2.32 ratios vs phi

  - sees strong epsilon-dependence to Ratios

  - Ratios at epsLO larger than Ratios at epsHI

  - GH: it is *very important* to look at the Ratios plots for each iteration

    - the goal is to get the Ratios having similar values for both epsLO and

      epsHI, otherwise any separated cross sections are not reliable

  - look more closely at the parameterization

    - GH: suggests to start with only P1 for sigL and P5 for sigT, setting

      others to zero initially

Ali

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Quick updates

- iFarm is very slow, but finished replays for two higher Q2 settings

  - will get these pi+ spectra to RT soon

- working on hodoscope efficiency plots for SHMS NIM paper

SIMC resolution study

- no HMS delta-corr needed for 3 of 5 kinematics, so can finalize SIMC

  resolution tuning

  - Q2=5.5, W=3.02 comparison of MM vs t-bin between new and Feb analysis

  - Feb had overall good agreement, but poor agreement vs t-bin, SIMC was wider

    than data at low -t

  - now doing tuning for all t-bins, to make sure SIMC is not wider than data

    anywhere

- DC resolution factor is now 4x instead of 9x

  - Q2=3.0, W=3.14 center: now 5 t-bins instead of 4

  - Q2=4.4, W=2.74 center

  - reasonable agreement of MM shape w/data

- now running MC for all DeltaPi BSA kinematics w/new resolution correction

  - will start MM shape study for 3 of 5 settings

- Dave: still don't understand why the correction factor is so large, but at

  least it's no longer 9x

- Vijay: suggests to look at xptar, yptar comparison, to make sure this is not

  adversely affected by the MC resolution tuning

  - definitely a *GOOD IDEA* to check this

Vijay

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Summer 2019 LT-sep analysis, Q2=0.38

- shows Yield Ratios vs phi-bin at epsLO w/o iterations

  - sees some unusual phi-dependence in the Ratios that doesn't make sense

  - GH: suggest to turn of LT, TT in initial parameter fit

  - Dave: notices a weird Left-Right asymmetry in the Ratio error bars, one

    side has dramatically smaller errors than the others, if there is

    reasonably uniform phi-coverage these errors should be more uniform

  - Tanja: suggests to look at Ratios separately for each SHMS setting to see

    if things make sense, will be helpful diagnostic for debugging

Alicia

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BSA update: looking at the 3 Q2-settings that don't need HMS delta-corr

- MM cut study

  - compare MM from data and SIMC, more zoomed in than Ali's plots

  - Q2=3.0, W=3.14, center Data is wider than MC

  - Data-SIMC agreement is best at Q2=5.5, but still wider than SIMC

  - what MM cut values to use?

    - Dave: prefers no lower limit cut at all, unless the lack of a cut

      introduces a problem (e.g. extra background)

    - Dave: upper cut 0.98 is too tight, likes 1.0 better

      - suggest to look at Data/MC vs MM and look where the Ratio plateaus for

        deciding your cut values

    - Tanja: the Ratio plateau will occur somewhere around 5-10 sigma from pi+n

      peak

- CoinTime windows for Random subtraction

  - CT spectra are now flat after earlier error fixed

  - can use 6 peaks Left and Right of main peak without issues

  - PID cuts are applied to the plot, but no HGC, and loose MM cut applied

  - Dave: suggests to look at yield of each bucket and stay away from that

    region where yield/bucket starts to decrease

    - GH: the roll off in the yeild will in principle occur at different CT for

      different settings, as the coincidence signal timing is TOF dependent

  - Nacer: where is there a region where peaks are merged together next to the

    first random peak?

    - Dave: it's just due to finite timing resolution and the fact that the

      prompt peak is so large

Nacer

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Resuming KaonLT Q2=0.50 analysis after calibrations

- H.gtr.beta plot is now centered at 1.0 after new calib

- SHMS P.gtr.beta vs P.gtr.dp shows a wiggle

  - Nathan: this is due to a minor fault in the Hodo calib but you can ignore

    it

- P.aero.npeSum vs P.hger.npeSum for K+ identification

  - HGC<3, Aero>3 NPE cuts used so far

  - will have to tune the cuts according to the data distributions

- CTime.eKcointime_ROC1 vs P.kin.secondary.MMK

  - can see small K+Lambda and K+Sigma dots amid large pi+ background

  - GH: can apply a MMK>1.05 cut to remove the big pi+n CoinTime peak and make

    it easier to select K+ CT cuts

- Ali: for these kinematics, you will find the RF cut to be very effective

  - Vijay: agrees, looked at these data earlier, with RF cut, you can get the

    pi+ CT peak to be smaller than K+ peak

- Nathan: eK cointime is not quite centered at 1

  - Stephen may have not set the CT offset quite correctly, you can tune it

- testing some Real/Random cuts to apply

  - MMK after random subtraction shows negative counts in DeltaPi region

  - needs more optimization as part of PID studies

Next Meeting

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- Thur Mar 14 @ 15:00 Eastern/13:00 Regina

  - KaonLT will go first

  - note the change in time for Regina people, because of USA daylight savings

    switch