Here's an updated comparison between the cuts in Weihong's thesis ("old cuts") and a "new" set of cuts.  Note: the "new" set is still being optimized and evaluated (as this blog is part of the evaluation).  The following list of cuts is divided into those common to both sets, followed by the cuts unique to each set.

Cuts Common to Both Sets

• photon energies > 1.5 GeV,
• pi0 p_T > 4 GeV
• M_gg < 0.6 GeV

Other Cuts in Old (Weihong Thesis) Cut Set

• Vertex Z position must be in +/- 150 cm.
• At least one tower in the event must have E_T > 1.5 GeV
• The E_T (using the origin rather than the vertex) of the hits must be > 1.5 GeV
• The central tower for each hit must have E_T > some Guassian function based on the phi and eta of the hit (parameters optimized using old Iron/Air MC)
• Total number of hits centered under the 6-18 towers used for computing the energy of the two hits must be no greater than 4.
• An "eta" computed by adding the radius of the vertex and the distance in the xy plane between the vertex and the position the pi0 would have intersected the Z=270 plane must be within 1.086 and 2.0.  (Note: if the vertex has very small transverse displacement, or if the phi of the vertex nearly matches the phi of the pi0, this "eta" is approximately the eta of the pi0 computed using the vertex.)
• Both photons in the same sector

Other Cuts in New(est) Cut Set

• Distance between photons < 25 cm
• Preshower energy for the towers under the two photons each < 40 MeV
• Energy in SMD for each photon / photon energy > 0.012 for each photon

Comments

The "new" cuts seem to allow more "false cluster splits" through for the IU algorithm, and may also be slightly reducing the signal for this algorithm.  For the TSP algorithm, the new cuts allow a larger amount of photon pairs, and possibly an increase in signal.  A reliable background subtraction method is needed to make stronger statements.