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Scalers

During a run, a number of electronics registers (scalers) would be used to count particular events, being reset at the beginning of every spill. Their information is essential for setting up and maintaining the optimal running conditions, and for obtaining probabilities of physically meaningful events (e.g., creation of a kaon in the $Pb+Pb$ collision) from the data. In particular, the experimentalist needs to know the number of beam particles crossing the target over the time of observation . Some fraction of the time, the data acquisition system is busy handling the incoming information and the new data can not be recorded. The triggers may be presented, but not accepted. This is the dead time of the experiment, and it can be large for some trigger conditions. The $SCBCL$ scaler records beam counter coincidences over the live-gated time. Alternatively, one can count beam counter coincidences continuously and, knowing the ratio of presented/accepted triggers, correct the beam count for the dead time.