2008.05.20 Shower shapes sorted by pre-shower, z-vertex and gamma's eta, phi, pt

Ilya Selyuzhenkov May 20, 2008

Gamma-jet algorithm and isolation cuts:

  1. Selecting only di-jet events identified by the STAR jet finder algorithm,
    with jets pointing opposite in azimuth:
    cos(phi_jet1 - phi_jet2) < -0.8

  2. Select jet1 with a maximum neutral energy fraction (R_EM1).
    This is our gamma candidate, for which we further require:
    • No charge tracks associated with jet1 (default jet radius is 0.7):
      nChargeTracks_jet1 = 0
      Note, that this charge track veto only works
      in the EEMC region where we do have TPC tracking
    • No barrel towers associated with jet1 (pure EEMC jet):
      nBarrelTowers_jet1 = 0
    • Ratio of the energy in the 3x3 EEMC high tower cluster
      to the total jet energy to be:
      R_cluster>0.99 (previous, softer, cut was 0.9)


  3. For the second jet2 (away side jet) we require:
    • That jet2 has at least ~10% of hadronic energy:


  4. Additional gamma candidate QA requirements:
    • Matching between EEMC SMD uv-strip cluster with a 3x3 cluster of EEMC towers.
      (in addition reject events for which we can not idetify uv-strip intersection)
    • Minimum number of strips in 5-strip EEMC SMD uv-plane clusters to be greater that 3.

Data sample:

  • pp2006(long) - 2006 pp production longitudinal data after applying gamma-jet isolation cuts
    (note the new R_cluster>0.99 cut)

Shower shapes sorted by pre-shower, z-vertex and gamma's eta, phi, pt

Note, that all shapes are normalized at peak to unity

Figure 1:Shower shapes for different detector eta bins


Figure 2:Shower shapes for different detector phi bins


Figure 3:Shower shapes for different gamma pt bins


Figure 4:Shower shapes for different z-vertex bins