Kaon_LT Experiment

                 Apr 11/24 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, Nathan Heinrich, Muhammad Junaid, Alicia Postuma,

   Nacer Hamdi, Ali Usman, Vijay Kumar

CSULA - Konrad Aniol

York - Stephen Kay

UVa - Richard Trotta

JLab - Dave Gaskell

CUA - Tanja Horn

FIU - Pete Markowitz

Richard

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Resolving various issues in KaonLT LT-separation

- RF time cut now removed

- -t distribution offset between data and SIMC

  - found that proton mass was used for detected particle instead of K+

- SIMC recon script did not use the updated kinematics to recalculate the

  weight

  wt'= wt*(sig/sigcm_sim)

- weights were not properly recalculated when doing an iteration

  - ROOT was always using the first iteration weights

  - an over-writing issue in ROOT script now fixed

- with these corrections, there is a significant improvement in the

  phi-distributions at high and low epsilon for the kinematic setting shown,

  Q2=3.0, W=3.14

Outstanding issues

- some mismatches remain between SIMC and data distributions

  - PMISS shape is off

  - Dave: this could be due to the SIMC model not yet being optimized, wait for

    more iterations to be completed before checking this again

- pion subtraction needs improvement

  - "clean" pion sample used for Q2=3.0, W=3.14 leakage subtraction clearly

    shows some K+Lambda events

  - Garth: need to be very careful with the pion subtraction, as it has a

    different epsilon-dependence than the true K+ events, and you don't want to

    induce an artificial epsilon-dependence to the data

    - also very important that both K+ and pi+ samples populate the same focal

      plane limits, i.e. can't have an HGC hole cut on one but not the other

Vijay

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Low Q2 pi+ LT-sep update

- unseparated cross sections shown for 3 epsilons

  - some weird issues remain with phi-distribution of lowest -t bin, although

    not as bad as last time this was shown

- preliminary separated cross sections for L,T

- no ratios or kinematic comparison plots shown, so it's impossible to provide

  helpful suggestion on what to look at

  - it's *VERY IMPORTANT* to also show diagnostic plots

Ali

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piDelta BSA analysis

- last week, showed some preliminary BSA results at Q2=3.0, W=3.14

- since then, the t-bin limits have changed

  - the issue is that the background in the Delta region grows immensely with

    -t

- HGC cuts are applied to remove K+Lambda contamination in piDelta region

  - *IMPORTANT* any SIMC plots need to have the same cut

- MM plots shown for new -t bins, 0-0.37, 0.37-0.60, 0.60-1.0 and total 0-1.0 

  - will exclude the 0.60-1.0 region since there are too few piDelta events

    there for a reliable fit

  - in process of doing MM fits for new t-bins

  - an issue with 0.37-0.60 region is that some phi bins (center setting) have

    very strong background, so getting a good piDelta fit is tricky

    - the SIDIS background grows much faster with -t than the piDelta does

Alicia

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pi+n BSA Q2-scan

- delta(FIT) error will be treated separately from delta(CUTS) error, since

  they're not of comparable size

  - doing RMS of both together results in under-estimate of total uncertainties

- LT'/sig0 data shown vs. Regge model curves from B-G Yu

  - much larger x-dependence than Q2-dependence

  - LT' at fixed t vs Q2 is mostly flat, but different for each x-bin

- overlay of LT' at xB=0.25, 0.40

  - xB=0.25 data sets at Q2=3.0,W=3.14 and Q2=2.1,W=2.95 overlap very well

  - xB=0.40 overlay has more scatter, but still small Q2 dependence

  - Dave: how different are the -t_min for the two xB=0.25 data sets?

    - the difference is quite small, about 0.01

  - Dave: since the Q2-dep is small, how about overlaying all Q2 and look at

    the x-dependence

    - Alicia will make a plot for next week

Nacer

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Low Q2 K+ PID studies

- using runs=6921-6978, Q2=0.5, TH_shms=9.79(left) for comparison

- Main cuts:

  - H.cal.eTotTrackNorm>0.5

  - H.cer.npeSum>2.0

  - 0.15>RFtime(corrected)>0.95

- RF time correction

  - applied an adhoc correction to remove xptar dependence

- Signal/Bkd study via a Gaussian fit + polynomial bkd

  - does fit vs RF time cut

  - apply both Low and High RF cuts, vary each one independently

  - optimum values: Low=0.15, High=0.95

    - throw away events between these limits, correponding to pions

- Best K+Lambda yield appears to be with only RF cut, RF+HMS cuts is similar

  - applying SHMS cuts greatly reduce the K+Lambda yield due to various

    inefficiencies, the extra clean-up of the MM spectrum is not worth it

  - Ali: there appears to be a small amount of piDelta contamination underneath

    the K+Sigma events

    - suggests to do a pi+ leakage subtraction, similar to what Richard is dong

    - Garth: since the RFtime is so effective, can use a tight RF cut to easily

      generate a clean pi+ spectrum for subtraction

- Next steps

  - RF cut efficiency, Lumi checks

Nathan

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PionLT lumi scans

- figured out a reasonable BCM offset for the runs in this scan

  - offset=-0.17uA

  - make scaler(ELREAL) normalized yield flat vs rate

- RelYield-NoTrack has a rate dependence (anti-boiling) indicating a LiveTime

  issue

  - TotalLiveTime(TLT) is too low at high rate

  - Dave: as an intermediate step, try using CPULT instead of TLT, the

    Electronic DeadTime should be very small

  - Richard: can use the CPULT to fine tune your cuts, then re-introduce EDTM

  - Nathan will add EDTM timing plots to investigate cuts

- Dave Mack sent a new BCM calib, but had difficulty w/replay, investigating

  - has a meeting with DM next Monday re. learning how to do BCM calib

  - Dave: do we know how complicated the BCM calib is?

    - the UNSER is very noisy, DM throws away UNSER points that are outliers,

      requires some judgement

    - Nathan: expecting to generate plots and have DM identify outliers to be

      removed, will still take less time than DM having to do all parts from

      scratch

Junaid

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- arriving at JLab on Tuesday night

  - Dave: beam studies on Wednesday, so a Hall C walk through is possible

PionLT Heep analysis

- Ali had pointed out that BPM calibs were wrong

  - slope values were right, but offsets wrong.  All updated now

  - raster config files were also wrong

  - there was an issue for two run ranges where only one pair of raster coils

    were operational, so the other had to be run at double current

    - this is also fixed

- Heep Effective Charge, corrected for TrkEff, but not Calor or Cer Eff

  - wrong BCM still used

  - for setting shown, the data normalized yield is ~2x SIMC yield, which is

    surprising

  - for a different run, the yield ratio is much closer to 1

- Richard: you need to use the kinematics recon script on SIMC data

  - unfortunately, this means the PM, etc. plots have to be redone again

- Dave: make sure you have the correct_eloss flag turned off in the SIMC input

  file

  - by default, SIMC both does energy loss, and corrects for it in the event

    reconstruction, but hcana does not correct for eloss, so you need to turn

    it off

Next Meeting

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- Thur April 18 @ 15:00 Eastern/13:00 Regina

  - PionLT will go first