1. Understanding the decay background for measuring fragmentation photons
Ali Hanks
Group Meeting
Sept. 24, 2007
9/24/07

2. Method Get fragmentation photons directly
Use h- conditional yields to select photons correlated with jets
Subtract decay background to isolate jet fragmentation photons
Tagging method for estimating decay photon background
Tag photons from 0's and 's directly
Estimate tagging efficiency as a function of the h- 
Include contribution from other decays using the  distribution
9/24/07

3. Two Major Issues False tagged background subtraction for 0's and 's
Two possible methods: Event mixing, resonance busting
Two sources of background:
uncorrelated combinatoric pairs
real jet correlations
Use PYTHIA to understand the limitations of both methods
Estimating the tagging efficiency
Using fastmc: throw p0's associated with "trigger" hadron using input pT and  distributions from data
Doesn't show same pT trend in efficiency as seen in data
Use PISA to understand detector effects that the fastmc is missing
9/24/07

4. Resonance busting
Reminder of background trend in data:
9/24/07

5. Resonance busting in PYTHIA
9/24/07

6. Minbias event mixing
Includes sector cut in mixed, without it mixed is above data at all pT
9/24/07

7. Minbias event mixing
9/24/07

8. Minbias event mixing in the data
In the data we can see a similar trend
9/24/07

9. Understanding the fastmc
Thus far the fastmc has shown a strong pT dependence not seen in the data
Some of this could be real due to the pT dependent /0 ratio when requiring a hadron trigger in the event (shouldn't be this large?)
Important to understand any possible detector effects
Using PISA we can do the same thing:
Efficiency defined as
Compare this to what we see in the fastmc
9/24/07

10. Understanding the fastmc
Reminder: data vs fastmc (where data is ratio of tag to inc)
9/24/07

11. Understanding the fastmc
PISA vs fastmc
9/24/07

12. Understanding fastmc vs PISA
PT dependence of photon quality cuts:
compare all photon clusters to simulated photon clusters that get detected and pass our quality cuts
1st: standard pc3 cuts: dphi>0.01 and dz>7
2nd: hard pc3 cuts: dphi>0.03 and dz>20
9/24/07

13. Understanding the fastmc
PISA vs fastmc including single photon efficiency in fastmc
9/24/07

14. 9/24/07