Data samples and colour coding

1. black: pp2006 data
2. open green: MC-QCD-TuneA, partonic pt 4-35
3. solid green:  MC-QCD-Perugia0, partonic pt 4-35
    (these not shown yet -> still generating data points)
4. open red MC-prompt-photon-TuneA, partonic pt 3-35
5. solid red MC-prompt-photon-Perugia0, partonic pt 3-35

Event selection

1. di-jets from the cone jet-finder algorithm
2. photon and jet are opposite in phi:
      cos (phi_gamma-phi_jet) < -0.8
3. pt away side jet > 5GeV
4. detector eta of the away side jet: |eta_jet_det| < 0.8
5. data: L2e-gamma triggered events
6. No trigger emulation in Monte-Carlo yet
7. MC scaled to 3.164^pb based on Pythia luminosity (no fudge factors)

Figure 1: Reconstructed photon candidate pt, pt_gamma (no cut on pt_gamma, pt_jet > 5GeV)

Figure 2: Partonic pt distribution (pt_gamma>7GeV, pt_jet > 5GeV)

Figure 3: Estimate of the contribution from low partonic pt,
only QCD-TuneA MC are shown (pt_gamma>7GeV, pt_jet > 5GeV)
Black line: Exponential fit to partonic pt distribution in 4-7GeV range
                   (pt_gamma>7GeV cut for the photon candidate)
Red line: Exponential fit extrapolated to the partonic pt range below 4GeV.
                Ratio of the area under the red line (integral pt=0-4geV)
                to the area under the green line (integral pt=4-35GeV) is 0.0028.

Comments

1. (based on Fig. 3)

   I would propose we drop both of the lowest parton pt bins,
   i.e. pt=2-3 and pt=3-4 (Inherited error for pt_gamma>7GeV < 0.3%)
   and instead use our CPU time to produce more
   statistics in the 4-35 partonic pt range.

2. (based on Fig. 2)

   There is a small difference between CDF-Tune-A and
   Perugia0 tunes partonic pt distributions
   even for the prompt photon Monte-Carlo.

3. Comparison with Perugia0 QCD MC is coming.
   Hopefully after that we will be able to decide what
   Pythia tune is better match the L2e-gamma data.