Dec 4-5/25 PionLT/KaonLT Analysis Meeting Notes ----------------------------------------------- (Notes by GH) Today: KaonLT will be discussed first Please remember to post your slides at: https://redmine.jlab.org/projects/kltexp/wiki/Kaon_LT_Meetings Thursday: Present ----------------- Regina - Garth Huber, Alicia Postuma, Muhammad Junaid, Nathan Heinrich, Nermin Sadoun Virginia - Richard Trotta CUA - Tanja Horn, Chi Kin Tam JLab - Dave Gaskell Alicia ------ pi+n BSA paper - PLB asked for a 3rd round of edits and sent to reviewer, even though the reviewer said further review was not required - the referee responded quickly, seemed slightly annoyed to have been asked again - PLB has now formally accepted the paper, trying to deal with copyright forms, running into yet more problems with their website - paper is also now on the arXiv:2512.01928 u-channel pi0 region investigations - Q2=3.0, W=3.14, low epsilon, SHMS center setting - Bill requested that Alicia try fitting both pi0 and DVCS simulations to the MM^2 data, rather than a fixed 90%:10% ratio - the fit looks surprisingly good: ~25% DVCS:75% pi0 ~100 counts DVCS vs 300 counts pi0 - project could be assigned to a future summer student to complete, now moving back to omega region analysis proton PID studies - tried a "geometric cut" on the AeroNPE vs RFtime distribution - for Q2=3.0, W=3.14 high epsilon, RF is available for Center and Right SHMS, but not Left - looked at MM, get a few more omega events but unfortunately also a few more pi+ events, the cut needs some fine tuning - the Left SHMS setting has no RF cut available, so more pi+ leakthrough - would probably need to apply a tighter Aero cut and a "geometric cut" on HGC vs Aero Junaid ------ Q2=3.85, W=2.02 LT-sep preparations - will show main plots tomorrow, today just a quick update - finished running SIMC for this setting - this setting has both Right-1 and Right-2 settings, which are different by about 1degree, apparently we did an HMS saturation test as part of run plan, they have to be analyzed separately - high and low epsilon have different Aerogel index - was using same Aerogel cuts, will have to investigate to see if any changes to the cuts are required Nathan ------ PionLT CoinLumi systematic uncertainties - reading Blok paper, looking at how to divide syst unc into scale, point-to-point and partly-correlated categories - Dave: overall systematic uncertainty scale comes from HeepCoin analysis, i.e. how well we are able to reproduce the known elastic cross sections - EDTM syst unc is evaluated by increasing errors to give ChiSquare=1 - Garth: can look at how the ChiSquare varies by rate - Tracking syst unc: Ali did not evaluate systematic uncertainties in his tracking study, will look into this - Dave: suggest to look at Abishek's thesis - SIDIS data are flatter, allow some systematic studies not easily possible with more rapidly varying exclusive data. Can take his values (with citation) where appropriate - also looking at Junaid's LT-sep scripts, will try to reproduce his Q2=3.85, W=2.62 results Friday: Present --------------- Regina - Garth Huber, Nathan Heinrich, Alicia Postuma, Nermin Sadoun, Muhammad Junaid, Nacer Hamdi Virginia - Richard Trotta CUA - Chi Kin Tam, Tanja Horn Ohio - Julie Roche JMU - Ioana Niculescu, Gabriel Niculescu FIU - Pete Markowitz York - Stephen Kay JLab - Dave Gaskell Richard ------- KaonLT Q2=3.0, W=2.32, low epsilon, Center SHMS - checking empirical fits of background near Lambda peak - current method: - first subtract pi+ leakthrough, this still leaves substantial background in Lambda region - then fit a quadratic to shoulder around MM=1.2 p0*(x-1.12)+p1*(x-1.12)^2 - finally fit a 2nd order Chebyshev to region under Lambda - this leaves an unfit background at MM<1.05, Richard asks if he should apply another polynomial to subtract this region? - *NB* Gabriel: you should try to use the Lambda peak shape from SIMC to guide you on how much background you need to subtract - you need to match the data to MC Lambda peak shape over a subset of the MM range (about 1.08-1.15) - only need to estimate background in that region - region lower than MM cut won't be relevant - estimate the background 2 ways: take the difference between them as a systematic - Nacer: your background fit is over a narrow MM range, maybe fitting over a broader MM range will give a more stable result - another possible method is SideBand Subtraction, avoids issues with challenging fit for each t-phi bin - empirical fit error calculation method - define normalized background yield in analysis window - propagate fit uncertainty to integrated background using the full covariance matrix - if covariance matrix is invalid, use diagonal approximation - evaluate using central differences - convert background-integral uncertainty into a fractional yield uncertainty - Chi Kin: try to avoid the more complicated formula using full covariance matrix, try using just the diagonal approximation - question for us: currently using a 25 count/t-phi-bin threshold in the analysis, if the threshold is raised to 100 counts, end up removing many t-phi bins - *NB* Garth: can you instead use your background error estimate to guide whether to keep the t-phi bin or not? - a clean MM histo with few counts might be easier to analyze than a high count MM histo with very uncertain background Chi Kin ------- KaonLT follow up to Richard's background investigations - method used: - first subtract Sigma0 MC to give a flatter MM dist to right of Lambda peak - then define 2 SideBands left and right of Lambda peak and fit a Chebyshev polynomial underneath the Lambda - issue: the Lambda radiative tail is oversubtracted, agreement between data and Lambda MC is good in main peak region, but poor in tail region - it would be better to fit sidebands and Lambda together - tried approximating Lambda MC peak with CrystalBall distribution and fit this together with the Chebyshev - this didn't always work, too many free parameters to fit - *NB* Gabriel: avoid the CrystalBall distribution, just fit SIMC and background directly to the data. This will have fewer free parameters - for the SIMC, just a scale and small MM offset to fit - Q2=3.0, W=3.14 LT-separations - changed from Richard's more complicated W-factor to Wfac=1/(W^2-mp^2)^2, i.e. same as Nacer - high epsilon Data/MC ratios slightly improved - low epsilon ratios improved too - lowest t-bin: high epsilon sig_uns ~25% larger than low epsilon - next t-bin: sig_uns fairly flat with phi, high epsilon ~10% larger than low epsilon - other 2 t-bins: high epsilon = low epsilon within errors - sigL has a significant t-slope - results look fairly encouraging Next week: plan to show first plots for Q2=4.4, W=2.74 Nacer ----- KaonLT Q2=0.50 LT-sep - found a good model for sigT, still working on sigL - the exponential function does not fit well, perhaps will move to flat or a polynomial function - HMS xptar Data vs MC comparison - Dave: looks like there's a consistent shift between them, the entire distribution needs to be shifted by 2.5mrad - the HMS matrix elements have an issue, likely the 0th order offsets were not included correctly when doing the fitting - this effect is seen also in other data sets, affects the phi reconstruction - Nacer uncommented the hphi_offset=-4.9E-3 line in his file and replayed data - the data shifts, but in the wrong direction, needs a positive offset - *NB* Dave: not sure where that number came from - please try hphi_offset=+2.8E-3 and htheta_offset=0 determined by DG using 2022 inclusive data - *NB* Nacer and Richard/ChiKin need to replay their data with this offset - Junaid is using Christine's HMS matrix elements and 0th order offsets determined with NPS data, sees no HMS xptar shift hphi_offset=+5.8E-4 - *NB* Dave: you need to check PionLT data for P_HMS<5 GeV/c, where older ME are being used - other distribution showing a shift is SHMS-xp_fp' - Garth: possibly this is caused by the HMS offset, since exclusive data are highly correlated between the 2 spectrometers - Dave: see what it looks like after modifying the HMS offset and we can discuss again Junaid ------ Q2=3.85, W=2.02 LT-sep preparations (continued) - Aerogel cut: 1.5npe - *NB* Garth: need to evaluate the pi+ cut efficiency for this cut - *NB* Dave: you are only showing the 1D Aero-NPE plot, it's impossible to tell whether this cut is what you need. Not saying that this cut is inappropriate, but rather that it is impossible to evaluate - please look at other variables with this cut, such as CoinTime - Garth: can also look at MM to see background near pi+n region - MM offsets: from fit of Data to MC - obtain offsets of 1-5 MeV - Diamond cuts - low epsilon diamond needs to be a bit tighter, to remove unpopulated regions in other SHMS settings and improve comparison with SIMC - high epsilon diamond seems too high in W compared to low epsilon, for both data and MC - *NB* Garth: please double check that standard.kinematics is set correctly - if it remains, then need to remove non-overlap region from low epsilon diamond Next steps: - will complete these studies, then move to t-binning Next Week Meetings ------------------ - Thurs: Dec 11 @ 16:00 Eastern/15:00 Regina - PionLT will go first - Fri: Dec 12 @ 11:00 Eastern/10:00 Regina - we will continue where we left off