Ilya Selyuzhenkov February 20, 2008

Short summary

After processing all available jet-trees for pp2006 (ppProductionLong),
and applying all "gamma-jet" cuts (which are described below):

• there are 47K di-jet events selected

• for pt1>7GeV there are 5,4K gamma-jet candidates (3,7K with an additional cut of pt1>pt2)

• Figure 1: 2,4K events with both pt1, pt2 > 7GeV

  

• 721 candidates within a range of pt1>pt2 and both pt1, pt2 > 7 GeV

Data set

jet trees by Murad Sarsour for pp2006 run, number of runs processed: 323
4.7M di-jet events found (no triggerId cuts yet)

Di-jets gross features

• Figure 2: Distribution of electromagnetic energy (EM) fraction, R_EM, for di-jet events (number of jets/event = 2).
  R_EM = [E_t(endcap)+E_t(barrel)]/E_t(total).
  Black histogram is for R_EM1 = max(Ra, Rb), red is for R_EM2 = min(Ra, Rb).
  Ra and Rb are EM fraction for jets in the di-jet event.
  Same data on a log scale is here.

   

  

Gamma-jet isolation cuts:

1. selecting di-jet events with one of the jet dominated by EM energy,
   and another one with more hadronic energy:

   R_EM1 >0.9 and R_EM2 < 0.9

2. selecting di-jet events with jets pointing opposite in azimuth:

   cos(phi1 - phi2) < -0.9

3. requiring the number of associated charged tracks with a first jet (with maximum EM fraction) to be less than 2:

   nChargeTracks1 < 2

4. requiring the number of fired EEMC towers associated with a first jet (with maximum EM fraction) to be 1 or 2:

   0 < nEEMCtowers1 < 3

    

Applying gamma-jet isolation cuts

• Figure 3: Distribution of eta vs number of EEMC towers for the first jet (with maximum EM fraction).
  Cuts:1-3 applied (no 0 < nEEMCtowers1 < 3 cut).

  

• Figure 4: Distribution of transverse momentum, pt1, of the first jet (with maximum EM fraction)
  vs transverse momentum, pt2, of the second jet.
  Cuts:1-4 applied

  

• Figure 5: Distribution of mean transverse momentum, < pt1 >, of the first jet (with maximum EM fraction)
  vs transverse momentum, pt2, of the second jet.
  Cuts:1-4 applied

  

• Figure 6: Distribution of pseudorapidity, eta1, of the first jet (with maximum EM fraction)
  vs pseudorapidity, eta2, of the second jet.
  Cuts:1-4 applied

  

• Figure 7: Distribution of azimuthal angle, phi1, of the first jet (with maximum EM fraction)
  vs azimuthal angle, phi2, of the second jet.
  Cuts:1-4 applied

  

• Figure 8: Distribution of transverse momentum, pt1, of the first jet (with maximum EM fraction)
  vs transverse energy sum for the EEMC towers associated with this jet.
  Cuts:1-4 applied

  

• Figure 9: Distribution of transverse momentum, pt1, of the first jet (with maximum EM fraction)
  vs transverse momentum, pt2, of the second jet.
  Cuts:1-4 + Et(EEMC) > 3.0 GeV