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Veto Results on pi0 Analysis

Veto Results on pi0 Analysis



September 8, 2005

I analyzed 10 files of run 5242 which was a pi0 production run with the carbon target. I selected events with 2 clusters only and reconstructed the pi0 from the 2 clusters. Next, I flagged the veto status for each cluster. Comparisons are shown below with a few veto/cluster combinations.

Here is a legend of the different colors:


Invariant Mass of 2 photons Invariant Mass of 2 photons (better view of pi0 peak)

Theta angle of reconstructed pi0's


September 15, 2005

In this section, I analyzed the same files in the previous section, but this time I selected events with only 3 clusters. I made calculated the invariant mass for different 2 cluster combinations and plotted the mass with the same veto status cuts listed above.


Number of clusters per event

Invariant Mass of 2 photons Invariant Mass of 2 photons (better view of pi0 peak)


September 22, 2005

I analyzed pi0 production data for events with clusters from 2 to 10. The plots below are from run 5242 (Carbon target) and 5267 (Lead target). The statistics in this example are low (1 run); however, the majority of the contributions to the pi0 peak are from 2, 3, and 4 clusters.


Carbon target

Lead target

In this figure, I made ratios of the mass spectra with veto cuts by the mass spectrum without veto cuts. The number of clusters selected was 2 and 3 per event.


Ratio of mass spectra for Carbon target run.


September 29, 2005

This time I analyzed all of the Pb target data and plotted the 2 photon invariant mass. With the full statistics, the veto cuts do a better job of reducing the background.


Lead target (all files)

Below, I fitted the mass spectrum for the 2 cluster events when there is no veto cut(left) and when the veto cut is set for both clusters to be photons(right). The mass of the peak is 0.131 GeV with a FWHM = 5.8 MeV.


Inv Mass w/ 2 cluster events and no veto Inv. Mass w/ 2 cluster events and both neutrals from veto

I focused on the pi0 peak of the right plot above to see what the fit was missing. The peak has a high mass shoulder and is not exactly gaussian.


Closer look at pi0 peak in the right plot above.


October 27, 2005

I implemented all of Dustin's cuts except for the elasticity and timing ones. The cuts are

  1. Cluster energy > 0.5 GeV
  2. x > 3.8cm, y > 3.8cm
  3. Total energy of 2 clusters in the range of 3.5 to 6.5GeV
  4. Mass of 2 clusters > 0.085GeV

Here is the result of these 4 cuts on the number of clusters per event.


Number of clusters after cuts

Here is the results on the comparison on mass by veto status. The colors are as follows


Inv. Mass by veto status

Here is the results on the comparison on mass by cluster location. The colors are as follows


Inv. Mass by cluster location.

In these two plots, I zoomed in on the pi0 peak for events with only 2 clusters.


Inv. Mass by veto status Inv. Mass by cluster location

Here are the theta distributions by cluster location.


pi0 theta by cluster location


November 18, 2005

Here is a legend of the different colors:


Invariant mass w/ both clusters in PbWO4

Inv. Mass w/ no veto cuts Inv. Mass w/ Veto cut=both clusters are photons Inv. Mass w/ Veto cut=both clusters are electrons