In beginning to think about the run9 pi0 and eta ALL analysis Willie and I thought about how best to make a clusterer using the BSMD and BTOW. First we wanted to see how the pi0s and etas distributed themselves among various possibilities in geometry in order to know what we have to look at it in various regions of phase space. Running some single particle MC from pythia with the vertex at (x,y,z)=(0,0,0), particles thrown flat in pseudorapidity, and with a cut on the energy asymmetry of < 0.9 we get the following geometric probabilities where a "pod" is defined as a 2x2 section of towers that has the same eta and phi strips for its BSMD readout.

The probabilities are broken up into 4 classes of events. They are detailed below (and there are images below that)

• Inter-pod Non-adjacent towers - This is when the two decay photons are in different pods and the towers of those pods that had the decay photons are not adjacent to one another. For adjacent we define it as being one of the 8 surrounding towers in a 3x3 grid around the tower of interest.
• Inter-pod Adjacent towers - This is the case when the two decay photons are in different pods, but the towers that contain the photon are adjacent in the way that was described above.
• Intra-pod - This is the case where the two photons are in two different towers within the same pod.
• Intra-tower - This the case where the two photons entered the same tower.

Calculated the decay angle and energy asymmetry probabilities for the pi0 and eta as well. They are shown below.