ACD Recon Upgrade - Identifying Ghosts

Introduction

Like the other subsystems, the ACD suffers from ghost hits. There are two sets of electronic channels

• PHA Processing:
  • Responsible for calculating the energy deposited in the ACD element
  • Relatively slow readout which suffers from ghost energy deposition
• Fast Discriminator:
  • Fire a simple veto when voltage reaches a certain value (calibrated to 0.45 MIPs)
  • Relatively fast readout and reset, not expected to suffer much from ghosts

The idea behind de-ghosting the ACD focuses on the correspondents between these two channels. For in-time events where the PHA analysis measures more than 0.45 MIPs, the trigger veto should have ~always fired. However, for out-of-time events, the PHA can still be > 0.45 MIPs, but the trigger will have fired and reset. Thus, we can identify some ghost hits as having more than 0.45 MIPs but no trigger veto.

Basic Numbers

Pure Ghost Sample

Data Set: Periodic GR-v19r4p1gr07
Pre-Filters: '(GltGemSummary&32) && CalEnergyRaw>5'

No Ghost BKG MC

AG with Ghosts

v19r4p1gr13

with FswGamState == 0

BKG with Ghosts

v19r4p1gr13
FswGamState == 0