Etothi Trigger Efficiencies
The Etothi part of the neutral trigger is designed to tag events were 80% of
the available lab energy is deposited in the CCAL. The signals from the 1280
lead glass blocks first go through the level 1 summers where the signals for
each block in a ring are summed. Thus, 20 signals leave the level one summers
(one from each ring). These signals then enter the Etot summer.
At the Etot summer the 20 signals from each ring are summed, after which
they go through an integrator and finally split. One set goes through the
Etotlo discriminator and the other set goes through the Etothi discriminator.
The Etothi discriminator is set to pass signals showing a energy deposit in the
CCAL at least 80% of the available lab energy from the p pbar collision. If a
signal passes the discriminator for Etothi, bit 8 of the NMLU is set. At the
MMLU, if bit 8 of the NMLU was set as well as bits showing a veto on H1*H2' OR and
Fch OR from the charged trigger, the Etothi bit is set.
To calculate the Etothi efficiencies, the signals from the 1280 CCAL blocks
are used to duplicate offline what happens in the hardware during data taking.
For efficiency calculations real physics events
must be used and
accordingly, pi0pi0 events from the Etotlo data stream were chosen. The events
were chosen with the following selection:
Once the pi0pi0 events were selected the
energies for the blocks were summed and compared with the 80% value of the
available lab energy. If the total energy was at least that big, an etothi
software trigger was recorded. A hardware trigger is present
when the MMLU input bit 3 is set. The calculated efficiency is a ratio of the number
of events with both the hardware and software trigger to the number of events
with a software trigger only.