HCal Reconstruction

Reconstruction for the HCal means zero-suppression, calibration, and corrections - or in other terms: the translation of raw amplitudes to hits calibrated to the MIP scale. Following processing steps are involved:

  1. pedestal subtraction
  2. calibration to MIP scale
  3. zero suppression
  4. correction of SiPM saturation, see SiPM Saturation details

Output of the reconstruction are hits (lcio::CalorimeterHit objects). A dedicated page summarizes which information is accessible how via the hit objects. This page summarizes the reconstruction strategies. Running instructions for the code can be found elsewhere. The same applies to detailed informations on MIP, Gain, and electronic intercalibration.

1. Pedestal subtraction

For now, pedestal subtraction is done by averaging over random trigger blocks in beam data and applying them for all beam events until the next random trigger block. Advantage: simple one pass on one file processing. Disadvantage: relatively low statistics

2. MIP calibration

MIP calibration constants are stored in the conditions database under

/cd_calice/Hcal/MIP/Approved       -- contains MIPConstants objects

As of today, average calibrations over longer data taking periods are stored. A more sophisticated application with temperature-dependent corrections is under study but not mature enough for application.

3. Zero suppression

Zero suppression is done by a cut on the MIP scale, steerable in the IntegratedHcalCalibrationProcessor. The recommended cut is 0.5 MIP for physics analyses. However, central reconstruction is done with a cut at 0.4 in order to allow systematic tests.

4. Saturation correction

Saturation correction is still under study and not fully understood. The best correction as of now uses individual response curves measured at ITEP before integrating SiPMs and tiles. The measurements are available from the conditions database in folder

/cd_calice/Hcal/ITEP_Saturation      -- contains TilesItepSaturation objects

In addition, the connection between hardware address (usually identified as 'module, chip, channel') and SiPM number needs to be made available, which is stored in folder

/cd_calice/Hcal/Production_DB        -- contains TilesProduction objects

The units needed for saturation correction is 'pixels', which means that both intercalibration and gain calibration constants are needed.

/cd_calice/Hcal/Gain/Approved        -- contains GainConstants objects
/cd_calice/Hcal/Inter/Approved       -- contains InterConstants objects

As of today, average calibrations over longer data taking periods are stored. A more sophisticated application with temperature-dependent corrections is under study but not mature enough for application.

HCAL Reconstruction (last edited 2009-10-21 11:40:09 by NilsFeege)