Nov 28/25 PionLT/KaonLT Analysis Meeting Notes ---------------------------------------------- (Notes by GH) 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, Alicia Postuma, Nacer Hamdi, Nermin Sadoun, Muhammad Junaid, Nathan Heinrich Glasgow - Rachel Montgomery, Kathleen Ramage York - Stephen Kay CUA - Chi Kin Tam Junaid ------ Setting up for PionLT Q2=3.85, W=2.02 analysis - completed RF cut studies. Using cut 1.2100 - yield+error>0 - yield ratio of the Lambda(1.10-1.14) region to pi+ region>5% - slightly adjusted t-bins, now has 4 t-bins and 12 phi-bins - still looking at adjustments to t-bin limits - Data/MC ratios - generally looks good, but gets some bumps in phi-distribution for the highest 2 t-bins - using sigT=p4*exp(-|p5*t|), monotonically falling - has questions whether this is a good form to use, Garth responds that T is expected to be fairly flat, but does not have to fall monotonically for K+, it could have a shallow hump in it, we will discuss this more in Nacer's presentation - no Q2 or W dependence in any of the functions. Nacer suggests to restore a simple W-factor - Data and MC focal plane and physics variable plot comparisons - comparison is notably worse for the Left setting than the Center setting - looking into further improvements - describing Sigma0 peak w/ CrystalBall function, as described earlier - sometimes this gave a long tail underneath the Lambda, leading to over-subtraction - looking at an alternate fit form to avoid this, Gaussian+Tail+Baseline gives a good description. Then exclude the Baseline, subtracting just Gaussian+Tail - some t-phi bins have a weird background between the Lambda and Sigma peaks which doesn't follow either fit form, the statistics for the shown bin looks marginal - looking at Landau distribution with a polynomial - *NB* Garth: is it essential that we retain these t-phi bins, i.e. if this same bin is populated more cleanly by a different SHMS setting, then it would be better to just exclude this bin (for both data and MC), rather than have a large systematic uncertainty from the poorly constrained background fit Nacer ----- KaonLT Q2=0.5 LT-sep refinements - trying different functional forms for sigT, while keeping L=LT=TT=0 in fit - simple Wfac=1/(W^2-mp^2)^2 form used - last week showed a fit that gave fairly good Data/MC ratios, the question is if this can be improved further, to give ratios more uniformly closer to 1 (rather than a t-dependent ratio) and fewer phi-wiggles - Try sigT=(p1*|t|+p2)*exp(-|p3*t|) - Data/MC Ratios fairly flat with phi, but ~1.6 for low -t, higher -t near 1 - the issue is that the model has difficulty accommodating the hump in sigT vs t, cross section drops too quickly at low -t, becoming negative - Try sigT=(p1*|t|+p2)^2 *exp(-|p3*t|) - this forces sigT to not go negative at low -t - ratios much closer to 1 at low -t, low epsilon, but high epsilon is worse ~1.3 - Try sigT=p1*exp(-|p2*t|)/(p3*|t|+p4)^2 - ratios look promising, phi-wiggles but under control - Also tried sigT=p1*exp(-|p2*t|)/(p3*|t|+p4)^2 - gave good ratios after 3rd iteration, except at low -t Next steps: - will go back to sigT=p1/Q^2 + |t|^p2/(Q^2+p3^2)^2 and introduce a simple function for sigL Alicia ------ Investigating the feasibility of u-channel DVCS info from KaonLT data - looking at plots of MM^2=EM^2-PM^2 to see how well DVCS and exclusive pi0 are separated - proton PID and random subtraction applied, but no dummy subtraction - default normalization in study: 90% pi0, 10% DVCS Low epsilon settings, no MM^2 shift is needed in omega region, so MM^2 reconstruction in pi0 region is presumably reliable - Q2=2.1, W=2.95 - DVCS region has poor statistics - Q2=3.0, W=2.32 - DVCS outside coincidence MM^2 region for this setting - Q2=3.0, W=3.14 - pi0 peak is mostly consistent with SIMC MM^2 shape, except for a shoulder on left side that is presumably DVCS - the shoulder indicates DVCS is more than 10% of pi0, could be as much as 20% - Q2=4.4, W=2.14 - also see a DVCS shoulder on pi0, but not as prominent as previous setting - Q2=5.5, W=3.02 - statistics are poor High epsilon settings, no diamond cut is applied to equalize to low epsilon acceptance - Q2=3.0, W=2.32 - MM^2 resolution is poor, but statistics are very good - DVCS region appears easier to interpret than omega region, due to fewer contributing processes - to describe DVCS region, would need both DVCS and pi0 SIMC plus a polynomial background - Q2=3.0, W=3.14 - applied a MM^2 shift, perhaps too far - Q2=4.4, W=2.74 - Q2=5.5, W=3.02 - bad statistics, will get worse if a diamond cut is applied In general, it appears there is enough there to be worthwhile for a MSc or undergraduate summer student to study in more detail. Will go back to omega analysis now - Q2=3.0, W=2.32 - investigate whether MM^2 rather than MM makes it easier to separate omega from pi+n leakthrough - conclusion: the separation between the peaks is larger with MM^2, but so is the width of each peak, so no difference in separation capability Next Week Meetings ------------------ - Thurs: Dec 4 @ 16:00 Eastern/15:00 Regina - KaonLT will go first - Fri: Dec 5 @ 11:00 Eastern/10:00 Regina - we will continue where we left off