Overview

The TRF processor is designed to measure the trigger efficiency of the SNO detector. Its inputs are data sets in which the trigger signals themselves are connected to the FECD (Slot 15 of Crate 17) and the detector is triggered asynchronously off of a source (typically the laserball). The output of the TRF processor is a titles bank (TREF, held in trigger_efficiency.dat) which holds the efficiencies and errors at each in-time NHIT value measured for each NHIT trigger type. In addition, there is an ntuple file (treff.ntp) which holds hbook-formatted versions of the information in the titles bank.

To measure the trigger efficiency, TRF applies sliding 93 ns window (corresponding to the trigger coincidence window) is applied throughout entire spectrum of hit PMT times to determine the maximum number of in-time channels, $\tilde N$, in each event. To determine whether or not a particular NHIT trigger fired in a given laser triggered event, the corresponding FECD channel is checked to see if it is in the event. In practice, there is an additional check on the low gain integrated charge (QLX) for any FECD channel in the event to ensure that the channel fired on a pulse from the corresponding raw trigger rather some sort of noise or pickup. Therefore, for a given value of $\tilde N$ representing the maximum number of hits in any 93 ns time window, the trigger efficiency is the ratio of the number times the NHIT trigger is observed to fire based on the FEC/D channels to the total number $\tilde N$ occurrences over all events.

The errors for the efficiencies are calculated using tables generated by Cousins and Feldman, to properly account for the fact that the efficiencies often run up agains the physical boundary (either 0 below threshold or 1 above).

For more details on the trigger efficiency analysis, please see the Analysis Report by Neubauer and Klein.