Attendees: Ashot, Chao G, Chao P, Dipangkar, Eugene, Haiyan, Li, Mahbub, Weizhi, Xinzhan.

Weizhi: Tried different reconstruction algorithms, but the small bump near the elastic peak seems to be independent of algorithm.
Module wrapper shifts peak.
W spectrum of events show the bump seems to correspond to the Delta resonance. Peter Bosted's inelastic ep model the dump seems to be confirm this. Adding the model to the simulation reproduces the bump, both for crystal and LG region.
Based on this study the estimated inelastic contamination is almost zero for small angle, and about 4-5% at large angles.
These will have to be subtracted. Try different models to get an estimate of the systematic uncertainty due to this subtraction.

Shifting the offset changes the ep/ee ratio, 500 um shift changes ratio by few %. When averaged over all quadrants there is no effect on the ratio (less than 0.5%).

Simulation has problems near the transition region as we have seen before, getting closer but there are still some issues (data has a brush like structure compared to simulation). The position information is from the GEM.
<TASK> Try plotting energy vs x and y position.

After event selection, the distributions are better but there are still some issues.
The two algorithm show some difference at the transition region. This is being studied more.



Xinzhan:

Used simulation to test the two methods. Both methods can reproduce the artificial offset set in the simulated data.

With better Hycal clustering the distributions have improved and now the method 1 and method 2 agree with each other and there is small difference from old offsets. Method 2 has a few outliers because of low statistics. Will use method 1 to generate the new offset table (already done, doing final checks).


Chao:
A final method is being worked on which includes the new information of the inelastic contamination. Will report next week.