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Kaon LT Meetings » mtg_23feb02.txt

Garth Huber, 02/03/2023 07:12 PM

 
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                 Feb 2/23 PionLT/KaonLT Analysis Meeting Notes
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                 ---------------------------------------------
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                           (Notes by GH and SJDK)
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                    Today: KaonLT will be discussed first
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Please remember to post your slides at:
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https://redmine.jlab.org/projects/kltexp/wiki/Kaon_LT_Meetings
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Present
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-------
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Regina - Stephen Kay, Garth Huber, Ali Usman, Alicia Postuma, Nathan Heinrich,
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   Vijay Kumar
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JLab - Dave Gaskell
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Ohio - Jacob Murphy
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CSULA - Yeranuhi Ghandilyan, Konrad Aniol
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CUA - Richard Trotta, Tanja Horn
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FIU - Pete Markowitz
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Vijay Updates
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-------------
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Update on Q2=0.38 low epsilon Analysis
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- CT peak, one peak either side of prompt peak looks very different (more
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  counts), one is 2 left of Prompt, other is 3 right of Prompt
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  for LEFT-2 SHMS setting only
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   - Possibly a different particle leaking in, but then why does this give
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     peaks on both sides?
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   - Should create 2D distributions to check this
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      - Plot CT vs MM
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      - CT vs Beta too
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   - TH: some weird random peaks were seen in Fpi-2 as well, but only on one
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     side, it is weird here to have weird peaks on both sides of prompt peak
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   - DG: yes, we can place cuts to avoid these weird peaks in the random
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     subtraction, but we should spend some effort to understand why they're
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     weird first
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- -ve events in MM distribution after Dummy and Random subtraction, to right of
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  neutron peak
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      - Green - central
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      - Red - left1
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      - Black - left2
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   - After dummy + random subtraction - over subtraction?
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      - Wrong charge assumed in dummy subtraction or similar?  *Check*
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- MM peak is also very off, wrong MM used?
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   - neutron peak is at 0.89, this is off a lot!
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   - Vijay thinks it is MMpi, could easily be MMK if using Richard's analysis
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     though  *Check*
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- Diamond cut on low epsilon data
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   - Cut shown for central setting
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   - DG: How was this done?
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      - Script maybe overcomplicating it?
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      - It should be a relatively straightforward set of cuts
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      - TH: Often it is nearly impossible to be sure exactly what you're doing
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        if a complicated script is used
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      - Each plot you make, you should be able to *understand* exactly what is
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        done to the data
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   - Some ragged blue region, it looks like SHMS+HMS acceptance cuts not
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     applied
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   - important to set the diamond cut after applying other physics analysis
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     cuts, apply to ALL three epsilon data, including low epsilon, for
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     consistency
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- RefTime cuts for this data?
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   - Originally said not set but then said it was, not 100% clear
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      - Think it's set ok?  *Verify*
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- t-binning
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   - Need same t bins for all three epsilon settings
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   - Lowest t bin will have nothing from left2
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   - Similarly highest bin will be only left2!
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   - Look at all statistics for three epsilons to determine t binning
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      - Apply diamond cut to mid/high epsilon, and other physics cuts too, such
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        as MM, etc.  Want the t-coverage and statistics to correspond
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        reasonably well to what will be seen in the final physics analysis
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- Data/SIMC comparison
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   - No scaling applied to SIMC, and normalization comparison looks
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     reasurringly good, as pion model should work very well at these
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     low Q2
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   - Pion model should be much better than kaon model to begin with
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   - SIMC distribution broader than data in xptar
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      - implies on some aperture in the simulation is "off"
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      - Which though? Very hard to determine
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      - This is a mystery
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      - Dave G has already updated target geometry in SIMC so it isn't that
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      - DG has no other suggestions, but notes that the same is seen in SIDIS
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   - SHMS yptar distributions SIMC, Data have same width, but a slight shift
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     indicating a small offset issue?
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Richard Updates
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---------------
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- Diamond cuts
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   - Q2=5.5 looks good
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         - Acceptance cut is applied, less ragged edges than what Vijay showed
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         - script crashes for Q2=2.11, investigating
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- t binning
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   - Apply all cuts
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      - PID
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      - CT
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   - Only one epsilon shown, will have to show both epsilons after diamond cuts
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     to determine optimal binning
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- t-distribution goes through zero (not allowed), lots of events at t>0
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    - Centre/left look OK
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    - Right PID looks bad
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         - Still clearly getting pi/p leakthrough
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         - Large delta background under lambdas that needs to be removed
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      - Try to get a clean pion sample, normalise this to residual neutron peak
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        with kaon PID
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         - Subtract it off
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         - Basically infer the shape of the pion background from selecting out
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           clean pions
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      - Likely have to similarly get a clean proton sample, and normalize to
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        residual omega peak, to remove proton leakthrough
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   - Something seems to have gone very wrong for the right setting
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     *Investigate*
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      - DG: maybe its an error pointing to a wrong calibration file?
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   - On plots, don't supress -ve counts
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      - Want to see where y=0 actually is, preferably by drawing a line there,
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        then can clearly see what's y<0
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- SIMC rotation matrix differs from what Carlos has
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   - Missing conversion from cartesian to spherical co-ords
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   - Definition of what theta/phi for central spectrometer mean differ too
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   - DG: Would it be easier to take output of SIMC and pass it through a
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     converter/script to adjust the values
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      - Copy what Carlos did and run this on the SIMC data
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      - Some modifications needed
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      - Should probably take values, convert them and save them to a new variable
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      - Could just be added to repository as a standard tool
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- In Bill's LT-sep code, definitely seem to be missing a script still
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   - Vijay noticed that there seems to be this missing link
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   - Should be called "average_ratios.f", or something similar, which combines
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     the different SHMS settings together to get full phi coverage
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- Average the ratios or sum the yields?
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   - Either way should work, see notes from 2 weeks ago (23/01/19)
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Alicia Updates
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--------------
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BSA pi+n Analysis from KaonLT
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- Fixed dummy target subtraction with correct thickness factor
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- widened MM window and NPE threshold in SHMS Aerogel
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- Q2=3.0, W=2.32, 5 t-bin results
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   - Asymmetry fits look a bit better now
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   - Bin 2 (0.21<-t<0.29) still has a different phi-dependence than the rest
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   - simple fit (A) vs full fit (A,B,C) differs by 2 sigma for Bin 2
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   - The last t bin is very wide, please *remove* high t tail
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- comparison of preliminary LT' with VR Regge model
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   - VR model has a known issue that is acknowledged in their paper
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      - Does particularly bad at high -t (> 0.5)
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   - VR curve does not extend to as low -t as the data
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   - GH: this is because the curve is calculated with central kinematics only
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      - need to compare VR to data at actual <Q2>,<W> for each t-bin
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      - lowest -t bin will have a lower -t_min than the central kinematics, and
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        the VR curve will then extend as low as the data
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   - even with these issues, the VR comparo to data looks reasonable up to -t=0.5
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- Q2=3.0, W=2.32 AL data
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   - asymmetry with dummy target data is consistent with zero to 1 sigma
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- Q2 = 4.4, W=2.74 first results
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   - again see the second bin doing its own thing
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   - difference between simple and full fits is only 1 sigma though
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   - AL BSA is consistent with zero within errors
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- Q2 = 2.115 results
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   - *need* finer t-binning, lots of stats
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   - full and partial fits different by <1 sigma, bin 2 issue seems largely
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     absent here
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- Looking at t-bin #2 more carefully
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   - starting to get K+ leakthrough in bins 4,5.  Bin 2 looks fairly clean
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   - background between pi+N and K+Lambda peaks also grows in Bins 3,4,5
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   - DG: Delta contribution seems to have a very different -t dependence to the
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     neutron contribution, see a kink at MM=1.05
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      - GH: piDelta has different t_min than pi+n, so that's why its absent in
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        Bins 1,2
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   - GH: wonders how big the pi+n radiative effects are for the higher t bins,
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     and whether this explains the extra counts left of piDelta
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      - we *need* to run SIMC for these settings and look at the growth of the
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        MM radiative tail with t-bin to better understand this
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      - will make a nice plot for the paper too
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   - DG -For weird second tbin, have you looked at asymmetry before combining
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     settings?
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      - AP: Yes, overlayed, hard to interpret as statistics poorer
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      - Nothing strange immediately jumping out
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      - Can *try* at low Q2, where there are more stats, but the weird effect
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        seems smaller there
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Jacob Updates
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-------------
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new HMS saturation curve including higher momentum data
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- Saturation correction in B sets in above 5.1 GeV/c
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- shows 12% effect at P=6.8 GeV/c
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- DG: Isn't this removed in the magnet setting program?
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   - checks, the program is unchanged since 2018-Aug-26
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   - JM: using B/I from readback, so this is the real effect    
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- Looking at Q1,Q2,Q3 saturation, expect to have more to show next week
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Nathan Updates
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--------------
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Detector time cuts update
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- Made an "open" cuts file
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   - Wide enough that whole distribution can be seen
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- Summing over PMTs since the're stable
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   - Doesn't change much between PMTs
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- Plots shown from run 13090, but other runs look the same
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   - Dashed lines with suggested cuts
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   - HMS Cherenkov looks odd
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      - All events at zero for H.cer.goodAdcTdcDiffTime_PMT2
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   - similarly variables for SHMS calorimeter all zero
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      - GH: unfortunately, hcana initializes all variables to zero, instead of
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        an error code of -9999, so it's not possible to distinguish a "true
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        zero" from an "error code zero".  Suspects this means the variable is
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        actually not present, which is not the same as being present but zero
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      - Maybe variable has been renamed to something else?  *Investigate*
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   - HMS Cherenkov distributions otherwise look fine
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   - HMS Calorimeter double peaks are seen
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      - most detectors have the right peak larger
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      - some detectors have both peaks
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      - others have left peak larger
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      - making cut wide enough to include both peaks for now
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      - GH: the bkd is down by 100X from the peak, so there is a bit more noise
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        leaking in with wider cut, but probably okay
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      - RT: yes, thinks so too
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Next Meeting
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------------
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Thur Feb 9 @ 17:00 Eastern/16:00 Regina/14:00 Pacific
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- PionLT will go first
(164-164/412)