Kaon_LT Experiment

                 July 3/25 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, Ivan Zhenchuk, Muhammad Junaid,

   Nacer Hamdi

JLab - Dave Gaskell

Virginia - Richard Trotta

CUA - Tanja Horn

FIU - Pete Markowitz

Junaid

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Q2=3.85, W=2.62 LT-sep

- now using functional forms from Tanja's thesis Eqn 5.9

  - initial parameters are same as Table 5.1 Final Values

- ratios using this parameterization are not surprisingly worse than with the

  Bosted global parameterization

  - high eps: R~0.7 at low -t to R~0.1 at high -t

  - low eps: R~1.0 at low -t to R~0.2 at high -t

  - we expect these ratios to converge rapidly to near 1 after a few

    iterations, the important thing now is the functional form that is tried

- still two scripts to write for LT-separations:

  - SIMC weight recalculation script

  - functional fits to LT-separated cross sections

- also still doing checks on correct error calculation method

Nathan

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PionLT deadtime investigations

- had a conversation with Dave last week about the unexpected time shifts that

  need to be corrected

- has all scripts working now to check if there is a difference if TCOIN.param

  is called, or ONLINE params

- can replicate timing shifts between:

  - explicit call TCOIN.param and implicit call standard.database

  - explicit call ONLINE param and implicit call standard.database

  - this means the implicit one is overwriting the explicit one

- the weird timing shifts must be coming from standard.database

- further to this, Nathan went through with Dave and identified some timing cut

  parameters that are too tight

  - if no good time is found within the window, it might be grabbing a garbage

    time instead

Nacer

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KaonLT Q2=0.50 Lt-sep

- also moved to Tanja's thesis parameterization

  - everything is the same as Junaid, except that mK substitutes for mpi in TT

    denominator

  - no plots to show yet, but ratios are generally similar to what Junaid

    showed, i.e. a decreasing ratio with -t while the Koltenuk model had flat

    ratios near 2

- discussion about the calculation of errors

  - MINUIT is the "gold standard" that all errors should be compared to

  - Nacer is using curve_fit in python

    https://docs.scipy.org/doc/scipy/reference/generated/scipy.optimize.curve_fit.html

  - Dave has confirmed on his own that using absolute_sigma=true in Python

    gives errors very similar to MINUIT

    - example call used by Nacer:

      curve_fit(fit_func, phi_all_fit, xsec_all_fit, sigma=err_all_fit, absolute_sigma

=True, p0=[0.04, 0.16, 0.00, -0.01])

  - Garth's quick script using PHYSICA fit

    - Dave agrees that "E2" error is the one to use, agrees well with MINUIT

Ivan

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KaonLT BSA analysis

- Q2=3.0, W=3.14 K+ sample that was missed last week

  - some phi bins are ~2 sigma away from zero, BSA~0.1, a bit bigger than

    the other K+ Q2 settings, of course statistics are better too

  - only one bin covering full t-range

- Q2=0.5 pi+ 5 t-bins

  - statistics are fairly good

  - BSA is somewhat larger for highest t-bin [0.067-0.11]

  - Nacer: some of the BSA plots are not left-right symmetric about phi=0

    - Dave: this is likely statistical fluctuations, not new physics

  - *NB* Garth: Ivan should take a look at pi+n event selection, PID systematic

    uncertainties

Richard

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KaonLT high Q2 LT-sep

- ran new functional forms for all settings

  - Good News! the new functional forms give reasonable results for ALL

    kinematics

- adjusting pion subtraction scaling for bad t-phi bins

  - previously was using a common background subtraction factor for all

    settings

  - now applying a separate factor for each t-phi bin, as Nacer does

  - this has a significant impact for some bins, as the factor varies from

    ~0.85 to ~0.2, depending on the bin

    - i.e. the pion background was significantly over-subtracted for some bins

      previously

  - the factor is determined by equalizing the integrals in the 0.88<Mk<0.92

    region between K+ spectrum and clean pion spectrum

  - hoping this will help the bins for which sig_uns is higher at low epsilon

    than high epsilon

- *NB* Garth: now that there is a common parameterization for all settings, it

   would be a good idea to make a plot of each fit parameter vs kinematics

   - see his LT-sep slides for an example

   - want to see if the parameter varies in some gradual fashion with

     kinematics, or not

   - this can give clues on whether there is a significant ingredient missing

     in the parameterization, or not

Next Meeting

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- Thur July 10 @ 15:30 Eastern/13:30 Regina

  - KaonLT will go first