"FineTime" Monitoring

The ATLAS L1 Calorimeter trigger(L1Calo) uses reduced granularity information to arrive at a trigger decision. Have a look here to get an overview of L1Calo. These reduces granularity signals or Trigger Tower signals are digitized by the Pre-Processor modules. For a good energy resolution to assign the event to the correct bunch crossing, the peak of the Trigger Tower Signal must be sampled precisely. Extensive work has been done to ensure this.

The goal of "FineTime" Monitoring is to check for any jitters in this peak sampling during a run. We start with an assumption that the analogue signal region around the peak can be approximated to a parabolic peak.

The Trigger Tower signals are sampled at 25 ns interval. For simplicity and ease, we do an affine coordinate transformation to make sample interval 1 ns and coincide the peak sample at the origin of the system.

Now the parameter "FineTime" is defined as the time for which f(t) is the maximum

* Also have a look at http://indico.cern.ch/getFile.py/access?subContId=0&contribId=1&resId=0&materialId=slides&confId=110246