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Kaon LT Meetings » mtg_24oct24.txt

Garth Huber, 10/24/2024 06:59 PM

 
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                 Oct 24/24 PionLT/KaonLT Analysis Meeting Notes
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                 ----------------------------------------------
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                                (Notes by GH)
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                     Today: Mark Jones will give a special presentation on
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                     hcana tracking improvements resulting from the VCS anaysis
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Present
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-------
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Regina - Garth Huber, Nathan Heinrich, Muhammad Junaid, Nacer Hamdi,
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   Alicia Postuma
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FIU - Pete Markowitz
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CUA - Tanja Horn
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JLab - Dave Gaskell, Mark Jones
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Mark
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----
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- VCS experiment saw a build up of events between photon and pi0 MM^2 peaks
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- noticed more than expected Chi-square>100 events in Heep elastics
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  - Heep plot of Chi-Square vs W^2 clearly shows the excess at large Chi-Square
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- tried various hcana algorithm improvements to find what was causing these
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  large Chi-Square events
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1) cut on DriftTime after StartTime correction is applied (removes 10-20ns
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  jitter)
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  - reduces # junk hits, but did not help large Chi-Square problem
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2) modified NewLinkStubs algorithm
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  - loops through Ch1,2 SpacePoints
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    - if Stubs in Ch1,2 pass: xt_track_criterion, yt_track_criterion,
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      xpt_track_criterion, then a track is formed
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    - if after above loops, no track is found, makes tracks from all Ch1,2
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      SpacePoint combos and picks the lowest Chi-Square combo
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3) made a NewFindSpacePoints algorithm
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  - old algorithm was ok, but since SHMS/HMS DC have similar layout, clustering
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    algorithm can be simplified
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  - make clusters of like UU',XX',VV' planes instead of pairs of unlike
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    planes
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  - then make combos of UU',XX' into UX clusters, VV',XX' into VX clusters
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  - have X,Y info from UX,VX clusters
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4) modify TrackFit algorithm to eliminate hit w/largest residual and do a new
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  fit
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- plot of SHMSxp stubs difference (StubXpdiff) of golden track
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  - set xp_track_criterion=0.4 to exclude tracks >0.4, <-0.4
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  - #possible tracks got a lot bigger than old code, since only one golden
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    track is selected per event, total #tracks should remain the same
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- Result: new code has 10X fewer events with Chi-Square>100, Heep W peak is
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  narrower
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- *NB* These algorithm changes are OFF by default, need to set flag ON and set
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  spacepoint criterion to implement
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  - *NB* most effective one is: TrackLargeResidCut
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  - only does track fit from stubs if residual was large
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- *NB* Mark has also updated the chamber alignment parameters, these are needed
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   for tighter residual cuts applied in the above algorithms
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- they are available from:
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https://github.com/JeffersonLab/hallc_replay/blob/master/PARAM/SHMS/DC/pdc_newalign_geom.param
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and
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https://github.com/JeffersonLab/hallc_replay/blob/master/PARAM/HMS/DC/hdc_newalign_geom.param
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- Nacer and Junaid will investigate if this makes an improvement to their Heep
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  replays
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Junaid
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------
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PionLT SHMS pi+ PID studies
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- fixed integral calculation, now #events do not drop as much when cuts are
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  applied
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  - used: Aero>2.5pe and 1.2<RF<3.4 cuts
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- check of plot of RFtime vs delta_SHMS
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  - if RFtime is correlated with delta, the correction for pi+ TOF is not
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    applied well
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  - *NB* Junaid will follow-up with Stephen about the TOF correction to RFtime
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- will need different RFtime cuts when beam bunch spacing changes
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  - *NB* also should check the cut for each SHMS setting, hopefully the TOF
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    correction reduces the SHMS momentum sensitivity, but this needs to be
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    confirmed
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  - Junaid will also do some cut dependence study
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Nathan
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------
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PionLT pi+ and SIDIS Coin Lumi scans
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- implemented Random substraction, results now look a lot better
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- LH2 pi+ Runs 14601-14606, now no-track and track plots have consistent drop in
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  yield slope, about 8% @ 70uA
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  - LH2 Runs 15816-15836, no-track and track also consistent
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  - LH2 Runs 16260-16276, also consistent
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  - LH2 RUns 16220-16242, NOT consistent, both show anti-boiling, but different
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    amounts
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    - doing checks, believes the CoinTime cut is letting in randoms
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  - SIDIS Runs 12218-12258 cover less current range than pi+
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    - no-track and track are constent, but slope might different than pi+, need
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      to do a proper fit to know for sure
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- Dave: the purpose of these studies is to compare them to the LH2 boiling from
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  singles and see if there are any extra deadtime effects in the coincidence
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  data
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  - Garth: yes, it seems very likely there is an extra effect, as the pi+
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    14601-6 yield drop is somewhat larger than expected for LH2 boiling
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  - *NB* since extra deadtime effects should be rate-dependent, not
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    current-dependent, we need to disentangle the two effects, can't just apply
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    a larger "effective" LH2 boiling correction
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    - for a given scan, current and rate are directly correlated, it is only by
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      combining different settings at same current but different rate that we
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      can disentangle them
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- *NB* preferred method would be to:
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  1) combine LH2 singles scans to get a more accurate LH2 boiling correction
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  2) apply this correction to the Coin Lumi data
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  3) overlay the different Coin scans, if they are consistent vs current, then
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     probably it is LH2 boiling
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  4) if they are inconsistent vs current, then overlay them vs different SHMS
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     rates to find the one that is most consistent, and use that to determine a
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     second correction to the Coin data
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- overall, the studies look very encouraging, hopefully we can complete them
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  sometime in November
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Alicia
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------
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BSA paper updates
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- PRL sent our response to 2 of 3 referees on Oct 22, still waiting on a
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  response
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Nacer
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-----
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KaonLT Heep singles @ 3.8 GeV
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- last week analyzed HMS singles, obtained R_HMS=1.037 +/- 0.011
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- found the problem with the SHMS singles replay
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  - needed to modify replay macro kin primary and kin secondary
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  - SHMS was analyzed as proton instead of electron, now get W peak
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- also checked SHMS PID cuts
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  - ended up using analogous cuts to HMS electron selection: CAL and W cuts
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  - no HGC, Aero cuts applied
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- obtain R_SHMS=1.017 +/- 0.016
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- Dave: it is very interesting that R_HMS is high
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  - suggest to look at Heep singles runs for other KaonLT energies to
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    investigate any systematic effects
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  - most interested in settings where SHMS/HMS are close to Coin setting
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    kinematics
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Next Meeting
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-------------
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- Thur Oct 31 @ 16:30 Eastern/14:30 Regina
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  - KaonLT will go first
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