Signal Reconstruction of the ATLAS Hadronic Tile Calorimeter: implementation and performance

TileCal, the central hadronic section of the ATLAS Calorimeter, is a sampling calorimeter made of steel and scintillating tiles. The TileCal front-end electronics read out about 10000 photo-multipliers at 40MHz measuring energies ranging from $simeq 30~MeV$ to $simeq 2~TeV$. The read-out system is designed to provide the ATLAS High Level Trigger with reconstructed PMT signals within the time budget allowed by the First Level Trigger maximun trigger rate of 75 KHz. The signal amplitude, time and a reconstruction quality factor are obtained for each PMT using Optimal Filtering techniques implemented in the Digital Signal Processors (DSP). After a short overview of the Tile Cal read out system we will discuss the implementation of Optimal Filtering algorithms highlighting the constraints imposed by the use of DSPs. We will report on the validation of the DSP algorithm and present the performances as measured in calibration and collision events.