Veto Analysis of pi0 Events from Pb Target

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.