Review of Veto Work

Calibration

• Timing - Done
• x position - Done
• y position - Done

Reconstruction

• Timing - not applied.
• Waiting for final calibration of tagger.
• Small effect (very little background in timing difference spectra).
• x position - Done
• y position - Almost Done.
• No correction needed for pair production and snake-scan calibrations.
• Correction needed for compton and pi0 production analyses.
• Veto2hycal - Almost Done.
• These are routines to match veto and HyCal hits.
• It fills the "veto" status of the hycalcluster bank.
• It is under investigation with physics analyses
• Pair production - efficiency ~ 96-97%
• Misidentified photons (false veto) ~1%
• pi0 production - ~3.5% (see plots below).

This study is a check of the veto cuts applied to the pi0 production events. I analyzed all of the Pb target data. The maximum number of clusters per event was 10, and the mass was calculated for each combination of 2 clusters. Below is a plot of the invariant mass with and without veto cuts.

The cuts applied were

• Cluster energy - threshold was set at 500MeV.
• Cluster xy - accept clusters with |x| > 4.5cm and |y| > 4.5cm

Here is a legend of the different colors:

• Black - No veto required.
• Red - Veto says both clusters are photons.
• Green - Veto says both clusters are charged.
• Blue - Veto says 1 cluster is charged, and the other cluster is a photon.

Last week, I showed a mass plot with a mysterious peak at 200MeV. It is present only in one Pb target run (4881). The mass spectra for this run is shown below.

Finally, I fit the pi0 peak in mass spectrum for no veto cuts(left) and with the 2 photon status from the veto(right). The yield after the veto cut is 3.5% lower than without the cut.

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