It was noted in a recent blog that requiring the eta of the pi0 momentum to be in [1.086, 2.0] decreased the efficiency.  This blog shows the eta distribution within the latest cuts, and shows that there is not a specific cut which is optimal over the whole pT range.

Cuts

The following cuts were applied:

• Both photon's in the pi0 candidate must have
  
  • energy > 1.5 GeV (IU), 2.0 GeV (TSIU) or 2.5 GeV (TSP)

  • energy in preshower 1 < 40 MeV

  • energy in SMD clusters (u+v) / photon energy > 0.006

• eta of pi0 candidate in 0.5 to 2.5

• mass of pi0 candidate in the window 0.1 to 0.2 GeV  (except for the plot of mass distribution, where the cut is mass < 0.6 GeV)

• pT in 4-5 GeV (low pT results) or pT in 10-12 GeV (high pT results)

Results

The results are attached at the bottom of the page, with a pdf for each algorithm and each pT region (low and high for this study).  The pages are organized as:

1. Distribution of the mass
2. Distribution of the eta
3. Distribution of the vertex Z for each pi0 passing cuts

Conclusions

The eta window corresponding to relatively good sensitivity varies significanly with the pT range, but not significantly with the choice of algorithm.  There is no strong motiviation for using this cut, as the cut does not really define the senstive region anyway, and there is no obvious choice for the placement of the eta cut were it to be used.  For now, this cut will not be used.

The vertex distribution does seem to be pT dependent, which accounts for some of the pT dependence of the eta distribution.