This blog entry will be used to collect ideas which I happen to think of for systematic studies for gammas.
Contents:
1.0 Underlying event studies / pileup studies
When evaluating purity vs efficiency (PVE) curves, if we get the underlying event wrong, or we get pileup effects wrong, then the PVE curves will be wrong. Too much energy will be in the isolation cone in data compared with Monte Carlo, and the MC events will show better purity and better efficiency.
How to address this?
1. Generate gamma trees
2. Select out gamma candidates with the "normal" set of cuts.
3. For each gamma candidate, define a "transverse region"
- the transverse region spans -1 < eta < 2, centered +/- 90 degrees in phi from the gamma candidate, and is 60 degrees wide.
4. Generate some detailed plots. I am most interested in seeing:
a. Track, tower and total multiplicity for -1 < eta < 2, and in eta bins
b. Track, tower and total ET spectra for -1 < eta < 2, and in eta bins
c. Track, tower and total multiplicty w/in R < 0.3 centered in the transverse region, plotted vs eta, plotted vs etacone - etacandidate.
d. Track, tower and total ET spectra w/in R < 0.3 centered in the transverse region, plotted vs eta, plotted vs etacone - etacandidate.
5. Repeat with pythia.
Comparisons between pythia and real data should allow us to "tune" pythia,
ala CDF.
Plots of ET sums, multiplicities, etc... as eta --> 1 will indicate how much energy "pileup" tracks are impacting the analysis.
A seperate, but related issue is how likely is the underlying event to trigger the charged-particle-veto. Or deposit significant energy in the postshower detector?
2.0 Optimizing the cuts
Can a better CPV cut (i.e. higher efficiency) be formed? What about a better analyzing cut (eg raise threshold and/or demand Epre2 < threshold)? By better, I mean what is the impact on the stat. and syst. uncertainties?
What about adding in transverse shower-shape cuts. Again, how do these affect the stat. and syst. uncertainties in the extracted yields?
3.0 Stability of yields with cuts
How do the yields vary as the "non essential" cuts are varied. e.g. the isolation cuts, shower shape cuts, etc...
4.0 Trigger Systematics
The background efficiency for satisfying the analyzing cut probably changes near the trigger threshold. The question may be "how low can we go" when setting the minimum pT for the measurement.
5.0 Beam Backgroud Effects
Look at the phi dependence of conversion rates using single photons from pion decays. Not enough etas w/ current finder.
