Kaon_LT Experiment

                 Aug 31/23 PionLT/KaonLT Analysis Meeting Notes

                 ----------------------------------------------

                              (Notes by GH & AH)

                     Today: PionLT will be discussed first

Please remember to post your slides at:

https://redmine.jlab.org/projects/kltexp/wiki/Kaon_LT_Meetings

Present

-------

Regina - Garth Huber, Nathan Heinrich, Muhammad Junaid, Vijay Kumar,

   Nacer Hamdi, Alicia Postuma

FIU - Pete Markowitz

CSULA - Konrad Aniol

CUA - Richard Trotta, Tanja Horn, Casey Morean

JLab - Dave Gaskell

Nathan Updates

--------------

Corrections to standard.kinematics went well.  Finished!

- pushed changes to GitHub yesterday

- no huge errors, only small corrections

- a few notable issues:

  - Target Mass: Corrected entries to use free proton mass rather than hydrogen

    atomic mass (in AMU). 

  - LD- runs, same for deuteron (use free neutron mass)

Next steps:

- will meet soon with Junaid to coordinate strategy

- need to double check Jacob's Hodoscope calibration, to be sure its set up in

  the database correctly 

  - if it was not entered correctly, it would affect Drift Chamber calibs, and

    some work would unfortunately need to be redone

- started writing batch scripts for full replay, which will be done after

  Junaid finishes calorimeter calibs

- Garth: are the report files ready for the new replay? 

  Nathan: need to add in NGC info

  - may want to add PID efficiency info

  - can probably do a full replay, then do 1st pass studies and optimize cuts

    for 2nd pass replay

- Richard: will clean up his Lumi scripts, particularly the EDTM calcs, so

  they're ready for Nathan and Junaid's analysis

Junaid Updates

--------------

Calorimeter calibs

- HMS 2021,22 calibs done

- now working on SHMS calorimeter calibs (negative polarity runs), should be

  done in a few days

- Cuts used for HMS CAL calibration:

  H.cent.npeSum > 7

  -8 < H.gtr.dp < +8

- Cuts used for SHMS CAL calibration:

  H.cent.npeSum > 7

  -10 < H.gtr.dp < 20

- the high SHMS npe cut is needed to select electrons (neg polarity runs only)

Nest steps:

- checking the hodoscope calibs (mentioned above) is the most important thing

  - will probably do a few DC calibs and compare, as a check

- Found Jacobs's hodoscope calib slides. He sent them to Garth and Nathan, and

  will post them on RedMine

Richard Updates

---------------

Luminosity analysis

- looked more carefully at getting a clean electron sample

  - Solved software bug which allowed bad events not passing cut to still get

    included in the analysis

  - fixing this helped a lot, much less scatter in the data

- Carbon HMS relative yield vs current: looks good

  - compare to Carlos Yero's Carbon and LH2 boiling factors vs current

- Carbon HMS Boil factor vs. ELREAL rate: looks flat without correction

  - (unweighed fit)

- Obtained corrections (error-weighted fits):

  Carbon: 1.85% +/- 2.1%/100uA (slight boiling)

  LH2: 4.86% +/- 2.8%/100uA

  - results are nicely consistent with Carlos'

- DG: the correlation for Carbon vs Current is tighter than the flat

  correlation vs Rate, this suggests a correction to the BCM calibration is

  needed, based on the Carbon vs Current correlation of 1.85%/100uA

  - then re-check Carbon vs Rate to see if the BCM correction introduces a

    residual rate dependence that needs to be removed (there might not be one,

    as the points get re-ordered on the rate plot)

  - finally, check the corrected LH2 correlation vs Current to get the final

    cryotarget boiling correction

Next steps:

- update SIMC for LT-sep analysis, needs to update the function in

  physics_iterate.f

  - was planning to start with the function in Marco's thesis

  - GH suggests to instead use the same function that Vijay has already tried,

    as it has more free parameters and is more flexible

  - Marco's analysis had many fewer statistics, and so could only use a simple

    function with fewer free parameters

  - GH suggests to get the subroutine from Vijay, as he already has it working

    - the only change that should be needed is to replace mpi with mK in the

      pole term part

Vijay Updates

-------------

- DaveG asked for hodoscope efficiencies per plane, needed to add to report

  file, still waiting for replay

Next steps:

- working on Luminosity Summer-2019 data

Alicia Updates

--------------

BSA Binning MC requested by DaveG

- the question to be answered is "how much difference does phi-binning make to

  the BSA fit results?"

  - Since some sets have limited number of bins, trying to find the adequate

    number in bins for beam asymmetry fits

  - generate random pseudodata with known inputs: A=3; B=0.8; C=0.3

- Fit breaks at: 5 phi bins, and at <= 100 entries 

- 9 phi bins fit OK w/ good statistics

- 11,13 phi bins OK except when stats poor

- second study with A=6; B=0.2; C=0.1

  - similar results

  - Deltapi data have poor statistics, study shows probably fitting only A is

    best

- real data Q2=5.5, W=3.02:

  - vary # phi bins and compare Full Fit to Approximated Fit

  - Number of bins do not change the beam asymmetry outcome up to 1 sigma

- recommended binning:

  Q2=5.5:         4 t-bins, 13 phi-bins

  Q2=4.4:         5 t,      13 phi 

  Q2=3.3, W=3.14: 7 t,      15 phi

  Q2=3.3, W=2.3:  7 t,      15 phi

  Q2=2.1, W=2.95: 8 t,      15 phi

  - Dave: Use same number of phi bins for all the plots, study suggests that

    the minimum number of bins, maintaining good fit in beam asymmetry, is 13

    bins.  Makes it a lot easier to explain in the paper

Discussion of new CLAS BSA paper:

  S. Diehl, et al., Phys Lett B 839 (2023) 137761 1-7

  - analysis of sigma_LT'/sigma_0 for similar kinematics to ours

- Our results are still important: expecting higher precision than CLAS-12

  - combining our data with theirs, we can do Q2-scans of LT' at fixed

    x=0.255+/-0.01, 0.415+/-0.01

  - Diehl's conclusion: JML Regge better at low Q2, GK GPD better at high Q2

    - however, Regge comparison to their data is actually never very good,

      while GK is equally good at low Q2

  - our Q2 scan at fixed x,t should provide a more definitive conclusion

  - Dave: Hall C should have significantly better t-resolution than CLAS-12, so

    t-bin migration will be much less of an issue

    - can do finer t-binning to better see rise in LT' at low -t

- considered whether we can reliably extract LT, TT from BSA A,B,C fits

  - used binning MC w/ known inputs and plot outputs to see how well we can

    accurately measure B->LT, C->TT

  - A=3; B=C=0, Nevts=1000: full fit does give a slight non-zero B,C and slight

    shift to A

  - leaning to not extract B,C values, as they are too uncertain

  - leaning to quoting weighted average for A fits as most reliable

  - the MC study has been very useful, definitely we can make use of these

  - results in the paper

- Diehl's paper used approximate fit and assign 3% systematic error from full

  fit

  - Alicia's MC study suggests that their errors largely underestimated

Garth Updates

-------------

In plane global offsets

- wrote a simple Fortran code to do a global analysis, took only a few days

  - code includes the Heepcheck derivatives and Vijay/Ali's input data, with

    global minimization

- unconstrained fit gives unrealistically large offsets to the beam energy, and

  this then drives unrealistically large HMS, SHMS momentum offsets

- then tried a constrained fit, keeping the beam energy offsets to not larger

  than +/-0.7E-3, based on the arc energy measurement uncertainties

  - Constrained fit works much better

  - Dave: obtained global offsets look plausible

    - SHMS momentum offset: MarkJ put in ad-hoc 2% correction, another 0.18%

      correction to this is reasonable

- GH can do a further study, including the three higher beam energy Heep data,

  will ask Richard/Ali for the shift data

  - it's not obvious whether the same set of offsets will work for the higher

    energy data, or not, as the HMS momentum gets quite high for some of them

  - will decide what to do after seeing initial fit results

Out of plane global offsets

- Vijay provided xptar info for three Heep coin settings from Summer-2019 data

- with these data included, offsets follow linear trend, with one exception of

  one data (3.8 GeV)

- Can Richard/Ali take another look at the replay of the 3.8GeV Heep data,

  there is clearly something wrong with it, maybe a wrong BPM calibration, or

  an error in standard.kinematics?

- to extract the final offsets from the linear fit:

  - need to locate the first order SHMS expansion coefficient in Matrix Element

    file

  - need plots of BPM data for several Heep coin settings

    - will differ from online results, due to newer calibration

    - offsets of up to several mm are reasonable

    - in principle, only 1 setting is needed, but best to do at least several,

      to check for consistency

Next Meeting

------------

- Thur Sept 7 @ 16:00 Eastern/14:00 Regina/13:00 Pacific

- KaonLT will go first

- Poll to see if this meeting time will continue to work for the fall

  https://www.when2meet.com/?21121667-zMYFn

  - so far, the best time appears to be Tuesdays at 16:00 Eastern/14:00 Regina