# Trigger system used in Delphi detector for mass and width measurement of Z boson

I am unable to understand the technical language used in Tigger section on page 543. Following were the texts I did not understand :

( I ) coincidences of back-to-back TOF sectors:

( 2 ) majority > 3 TOF sectors:

( 3 ) majority >2 HPC sectors:

( 4 ) coincidence of any TOF with any HPC sector.

For hadronic Z° events with a sphericity axis between 50° and 130° the following efficiencies were obtained:

TOF triggers alone ( 1 + 2 ) : 95.5%,

HPC trigger alone (3): 81.4%,

TOF, HPC trigger (4): 96.4%,

Overall trigger: 99.5%.

What do these texts exactly mean?

The triggers that you have described above rely on fast elements in the detector (the hodoscope-based time-of-flight system and the high-density projection chamber) and just ask if they've seen activity in widely dispersed angular directions (which is what you expect from the decay of $Z$ generating annihilation).