Offline Shift System - HELP

Z Filters

Pass1

This filter depends entirely upon quantities computed online, viz numbers of EM towers with energies above either a  low or high threshold.

The cuts are:

• linear cuts on energy sums for the high and low thresholds, plus a correlated cut
• there be at least 10 high-threshold towers
• there be non-zero high-threshold towers in both North and South.

This filter is somewhat prone to noise (otherwise we wouldn't need a Pass2!), but historically, ratio of EIT1/(Precise Bhabhas) has been around 0.85.

Histogram Descriptions

• EHLW 
  • sum of high-threshold tower energies vs sum of low-threshold tower energies
• NEMH
  • number of high-threshold towers
• NHNS
  • number of high-threshold towers in the north vs those in the south

Pass2

This filter makes use of cluster-finding in the LAC. Good clusters have

• E(raw) > 100 MeV
• E_EM1 + E_EM2 > 0

For these clusters, event cuts are:

• SE > 15 GeV
• Energy Imbalance < 0.6
• More than 8 clusters if the thrust axis is in the barrel or 11 in the endcap

The ratio of bhabhas to Z's is traditionally 2.08.

Histogram Descriptions

• FETO 
  • total raw energy of good clusters
• FEIM
  • energy imbalance (0 < Imbalance = [Vector energy Sum]/E_tot < 1)
• FCLB
  • number of good clusters for events with the thrust axis in the barrel (|cosq|<0.8.
• FCLE
  • number of good clusters for events with the thrust axis in the endcap (|cosq|>0.8.

TAKAL Filter

The EIT2 filter was deemed to have ~0.3% background. It was found that for a small efficiency hit, this background could be lowered to 0.1% by requiring tracks in the event and not cutting on the number of clusters. The same cuts on total energy and imbalance as EIT2 are applied, plus:

• More than 3 tracks in either the north or south hemispheres or at least one in each hemisphere.

The ratio of TAKAL/EIT2 is expected to be 0.97.

Histogram Descriptions

• TTFB 
  • scatterplot of number of good tracks in north vs south hemisphers