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Kaon LT Meetings » mtg_22oct05.txt

Garth Huber, 10/05/2022 05:35 PM

 
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                 Oct 5/22 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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Regina - Garth Huber, Stephen Kay, Ali Usman, Love Preet, Alicia Postuma,
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   Vijay Kumar
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CSULA - Konrad Aniol, Erika Gwin, Johnathan Conrad
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Ohio - Jacob Murphy, Julie Roche
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CUA - Richard Trotta, Tanja Horm
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JLab - Dave Gaskell
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FIU - Pete Markowitz
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Richard Updates
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---------------
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- Bill's LT-separation code
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   - Two bugs to deal with, going to contact Bill soon
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      - C++ compiling issue
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- Luminosity Updates
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   - Low beam on time runs
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      - Previously used BCM4A, used BCM1
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      - One variable index was set to 4A rather than 1
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      - Current cut applied on BCM4A - which was reading 0
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      - BCMs can be very different, 1 seems to work best
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         - I think this is the one Dave M recommended?
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   - Should use GoodStartTime in addition to GoodScinHit
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   - Tracking and PID cuts improved
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      - separate pi, p cuts for SHMS +polarity
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      - GH: could take all valid positive particles instead
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   - Things starting to look a lot better, particularly with the relative yield
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     without tracking
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      - Possibly correlated with weird behaviour of tracked yield?
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      - Finds that a discrepancy between EDTM-LT and CPU-LT is often due to bad
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        current cut
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   - 10.6GeV Lumi scan:
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      - SHMS relative scaler yield still looks odd
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        Carbon +14% slope @ 60uA
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        LH2 +30% slope
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      - SHMS untracked carbon looks very good except for 1 outlier
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      - SHMS tracked carbon still has 25% slope @ 70uA
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      - overall HMS scans looking good
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   - 8.2GeV Lumi scan (both spectrometers negative):
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      - change to BCM1 dramatically improves things, as most runs were
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        completely cut out when using BCM4A
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      - LH2: might actually see real -5% boiling, as trend is consistent across
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        scaler, untracked and tracked analyses, on both HMS, SHMS
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   - 6.2GeV Lumi scan:
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      - only 3 runs that look good (so far), up to 30uA
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      - this needs to be rechecked
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   - -ve polarity luminosities looking OK, converging
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- HeeP Uncertainties
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   - Included uncertainties
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   - Stat uncertainty on Cherenkov?
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      - DG: Should be a global efficiency that doesn't vary run to run
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      - determine this via a dedicated Cherenkov efficiency study (HMS)
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   - Dave G
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      - Uncertainties probably should not just be sqrt(n)
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         - This is an overestimate
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         - Binomial errors instead
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           https://en.wikipedia.org/wiki/Binomial_distribution
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         - Cherenkov efficiency is like a Yes/no question each time
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- To do
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   - Bill's cross section code
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   - Lumi Analysis
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   - Fast Raster Correction from FPi2
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      - *Might* already be done in hcana?
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      - In Fpi2 the calibration was off, can take a look
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   - Beam/target positions
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      - confirm dimensions compared to Dave Meekins write-up
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      - DG old document (2007) from XEM experiment
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      - DG: F2 people looked at this in Spring-18 data, need to locate this in
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        the hclog
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   - Calorimeter calibrations
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   - HGC efficiency calculation (Ali has write-up, need to add to code)
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      - Aerogel efficiency too
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Discussion 
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----------
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- SOS spectrometer acceptance cut in Data
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   - Mentioned in Blok paper
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   - Finds the boundaries of the acceptance
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   - Measured DIS scattering from deuterium, detailed comparison with SIMC
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   - SOS suffered significant saturation effects, which why it was needed
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   - this was not needed for HMS, should also not be needed for SHMS
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- Richard mentions a tool to port in papers to a bibliography quickly
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   - https://www.zotero.org/
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Vijay Update
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------------
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- Mainly writing committee report
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- Updated shell script for lumi analysis, processed relevant lumi runs for low
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  energy data
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   - Need to process data through yield scripts
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   - Yield vs Current study is next after the report is done
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Discussion
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----------
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- Error bars on the momentum offests
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   - Figure 4.7 (page 61) in Jochen Volmer's thesis -
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     https://misportal.jlab.org/ul/publications/view_pub.cfm?pub_id=5412
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   - How were the error bars here determined?
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      - From examining width of W peak?
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      - Yes, based on sensitivity from kinematics (Delta-W)*(dp/dW)
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   - seems to be a fixed +/-0.1% uncertainty for 5 highest points
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   - One point has very large error bar
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      - Vijay notes that this point also has an angle offset
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      - Magnets should really behave in a smooth and consistent way
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   - Expect a trend on both spectrometer momenta, not neccessarily a trend for
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     the angle (should be reproducible at the same angle)
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      - Generally have a single in-plane angle offset
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         - What about the vertical angle offset?
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            - Dave G doesn't recall seeing this for Hall C in the past 
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            - Could SHMS have affected this? Heavier than the SOS, and Walter
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	      says the hall floor has sagged
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      - Expect small point-to-point variation in the angle offset
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   - Start with one angle offset and one momentum offset in each spectrometer,
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     and see if you can get a global solution, allowing only a small
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     point-to-point variation
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Ali Updates
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-----------
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- Also working on committee report
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- BCM "calibrations" (the one that checks the beam on/off periods) for Lumi
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   - Double check whether this was done for the HeeP analysis
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   - Wasn't, added scaler replay and this determination back in
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- Will check the uncertainty in the efficiencies, as per our discussion
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Jacob Updates
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-------------
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- Chatting to Peter Bosted
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   - Posted something to SIDIS log
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   - He applied 6.2 GeV HMS matrix, sharpened peak and reduced MM tail
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   - should have beter agreement with MC peak shape now
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Stephen Updates
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---------------
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- Discussion of John Matter's proton absorption spreadsheet
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   - Lots of the legwork is done, a few things we'll need to adjust
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   - probability of proton coming in, that gets through for trigger
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   - material thicknesses in g/cm2
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   - uses average of nuclear collision length (Lambda_T) and nuclear
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     interaction length (Lambda_I)
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   - probability goes as p(x)=exp(-Sum(x/Lambda)) for total absorption
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   - this is based on the idea that won't lose elastic scatt (forward) in
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     trigger, but can lose multiple elastic scatterings
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   - calculation is for 2.25 hodo planes, corresponding to minimal 3/4 trigger
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   - Switch proton Lambda values to pion/kaon as appropriate
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      - Kaon values not directly available
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         - Scale pion values by difference in cross section at sqrt(s) for our
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	   reaction?
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         - Need to make some reasonable assumption that we can justify and use
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	   this
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         - plots of pi/K cross sections p.782 of current version of PDG
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   - Need to switch HGC gas from CO2 to C4F10 as actually used in our expt
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   - Remove NGC and replace with scattering chamber as needed
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   - Adjust aerogel based upon refractive index used, i.e. density scales as
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    (n-1)
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   - Adjust LH2 thickness depending upon spectrometer angle
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Next meeting: Wed Oct 12 @ 9:00 Eastern/7:00 Regina/6:00 Calif
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   - PionLT will start first
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