Kaon_LT Experiment

                 Apr 18/24 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, Ali Usman, Vijay Kumar, Nacer Hamdi,

   Alicia Postuma

CUA - Tanja Horn, Casey Morean

UVa - Richard Trotta

York - Stephen Kay

CSULA - Konrad Aniol

Nathan

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PionLT BCM calibrations

- met with Dave Mack on Monday to learn how to do the calibrations

- things going very well, made some improvements to Dave's scripts

- waiting for feedback from Dave Mack on results NH analysis

The steps:

- do a scaler replay of BCM calib runs

- pick beam on/off times

- do a fit of BCM frequency vs Unser current

- look at fit residuals, and exclude outliers

Initial results:

- it looks likely that BCM slopes and intercepts can be combined for periods

  where the physical configuration (PreAmp setup, tune) did not change

- BCM2 intercept and slope looks pretty stable

- DaveM thinks BCM4A is most reliable, as it generally has less non-linearity

  at high current

  - KaonLT used BCM4A and BCM1

- BCM4B is optimized for low current, saturates above 40uA, so calib will be

  done only for lower current portion of scans

- Nathan will make a write-up on changes to code and instructions

Richard

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mc_recon script changes

- as shown last week, there was an offset to some kinematic distributions

  because the recon script was using proton mass (left over from Heep) rather

  than K+ mass

  - after the fix, MM VS yptar correlations look similar for data + MC

  - some odd looking correlation between MM and xptar shown(!)

pi+ leakthrough subtraction

- now using an HGC cut, K+Lambda peak in pi+ sample is eliminated

- investigated variations to pi+ spectrum when varying HGC cut

  - no significant changes seen for NPE>1.5 to 3.0

  - also looked at variations in Aerogel cut

initial iteration results (Q2=3.0, W=3.14 only)

- sigL seems to have a fairly small Q2-dependence within the diamond

- t-dependence still not right yet

  - using exp(-t+0.2), will need to adjust the +0.2 offset in the exponent

- GH: the MMk spectrum after pi+ leakthrough subtraction looks nicely clean

  now, suggest that you try fitting the SIMC K+Lambda and K+Sigma peaks to the

  pi+ subtracted MMk data

  - the K+Sigma peak sits on top of K+Lambda radiative tail, it would be good

    to see what the comparison looks like

Alicia

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- making plots for the BSA paper

  - CoinTime, MM data vs SIMC w/cuts shown

  - sample asymmetries vs phi for Q2=3.0, W=3.14 (2nd highest stats setting)

BSA xB dependence

- last week we saw there is nearly no Q2-dep to LT', so it was suggested to

  explore the xB dependence by fixing -t (but not Q2)

- plots of LT' vs xB shown at -t=0.17, 0.27, 0.31, 0.36

  - 0.17: shows an interesting trend, all of these points are in similar

    Q2-range

  - 0.27, 0.31, 0.36: xB dependence is flatter, generally good agreement

    between Hall C and CLAS results

    - some discrepancy between Hall C and CLAS results at 0.27, which cannot be

      traced to Q2-dependence, as both sets bracket similar Q2-ranges

- don't yet know whether will include in paper or not

  - if we do, we probably won't compare to any theory curves

  - since the Q2-dependence of the data is ignored when making these plots, and

    the Q2-dep of the models differs from the data, this would be a messy

    comparison

Ali

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- last week saw that Q2=3.0, W=3.14 data at high -t had few piDelta events

  - proposed to exclude highest -t region which had many fewer piDelta events

    than background events

- similar study extended to other settings:

  - Q2=3.0, W=2.32, one t-bin

    - exclude events for -t>0.9, based on t-coverage of events in piDelta MM

      cut

  - Q2=4.4, W=2.74, one t-bin, exclude -t>1.0, region is tuned separately for

    each setting, based on how the MM plot looks at high -t

  - Q2=5.5, W=3.02, one t-bin, exclude -t>1.05

- Q2=5.5 phi-coverage

  - found that the piDelta MC somehow changed phi-range to 0-2pi instead of -pi

    to +pi

  - fixes underway, but source of the problem is not yet understood

    - one possibility is an issue with mc_recon

  - Richard: the phi range in hcana is different than SIMC

    - Ali: this is not the issue, that was already taken into account in the

      code, this is a kinematics-dependent change

  - Ali is still testing mc_recon script if it is using correct Mpi instead of Mp

Vijay

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- planning to show diagnostic plots next week on LT-separation

  - full set of plots not ready yet

Nacer

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KaonLT Low Q2 Cut Efficiency studies

- RFtime vs MMk

  - will use data to determine the fraction of excluded KLambda, KSigma events

    excluded due to the RFtime cut

  - since the pi+n MM region is clean, will select these events for the study,

    under the assumption (seems reasonable) that the RFtime distribution is the

    same for pi+ and K+, just shifted in phase

  - apply same cuts (but shifted) to pi+n events as used for K+ selection

  - get an efficiency of 0.987, high epsilon 4.9GeV data

  - will have to repeat study for low epsilon data

HMS electron selection efficiency studies

- quick check using physics data, rather than Heep data

  - For the Cherenkov, get an efficiency of 0.981, which still contains some

    pi- contamination

    - Ali: for higher Q2 KaonLT, the sample was not as clean, got efficiencies

      as low as 0.75, even after using tight Calorimeter cuts to clean up the

      event sample

    - looks like it's good to use Ali's electron efficiencies

pi+ subtraction sample

- the idea is the same as Richard's, except that a very clean pi+ sample can be

  obtained just by using a tight RFtime cut

  - still need to normalize the pi+ sample to the leakthrough

    - Richard: takes MMk region 0.89-0.93, scales to equalize integrals

Next Meeting

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- Thur April 25 @ 15:00 Eastern/13:00 Regina

  - KaonLT will go first