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    README file for ALICE Time Of Flight Detector Offline Code
    ==========================================================

Intorduction
------------

This is a short overview of the TOF code within the AliROOT framework.
Some additional details have been introduced to 

Structure
---------

There are 3 libraries build for the TOF. These are 

* libTOFbase:
  This contains the basic stuff, like data classes and managers. 

* libTOFsim: 
  This contains code used by the simulation only. This includes the
  detector class, AliTOF, and its derivatives. It also contains the
  code for building the geometry, as well as the (s)digitisers, raw
  data writer, QA checker and data containers.

* libTOFrec:
  Code needed for the reconstruction. This includes the reconstruction
  code itself, as well as cluster and track containers and QA checker.

The content of these libraries is detailed more below. 

libTOFbase:
-----------

Till today (February 6th 2008), it contains the following classes

  AliTOFGeometry:
	Manager of TOF geometry data. All code queries this manager
	for geometry parameters, so that the data are always consistent. 
  
  AliTOFdigit
  AliTOFrawData
  AliTOFHitData
  AliTOFHitDataBuffer
	Base classes for digits and real digits. They are all data
        classes that hold the TOT and TOF values for a single sensitive
        TOF element.

  AliTOFChannelOffline
  AliTOFChannelOnline
  AliTOFChannelOnlineStatus
  AliTOFcalib
  AliTOFDataDCS
  AliTOFFormatDCS:
	Calibration data classes.

  AliTOFRawMap:
	A map of (AliTOFrawData) indices.
        The AliTOFRawStream class uses this map to store raw data
        before making digits or clusters.

  AliTOFDecoder
  AliTOFRawStream:
	Classes to read raw data files.

  AliTOFAlignment:

  AliTOFPreprocessor
  AliTOFPreprocessorFDR:

libTOFsim:
----------

Till today (February 6th 2008), it contains the following classes

  AliTOF:
	Manager for all TOF simulation code.

  AliTOFv5T0
  AliTOFv6T0:
	Simulation drivers for the TOF detector.
	AliTOFv5T0 corresponds to a simulation where services are not
        completly described
        AliTOFv6T0 contains a more detailed description of all TOF
        detector components.

  AliTOFhit
  AliTOFhitT0:
	Base classes for hits. They hold the geometrical and physical
        informations of a single sensitive TOF element, like the ALICE
        coordinates, the detector indices, i.e. 5 integer numbers
        (sector, module, strip, par-row and pad numbers), the hit
        coordinates in the pad reference system and the
        time-of-flight measurement. Moreover, they hold also some
        additional measurements, like the momentum components, the
        energy loss in the sensitive TOF element and the track incident
        angle on the pad. Only the AliTOFhitT0 object contains also
        the track length measurement.

  AliTOFSDigit:
	Base classes for sdigits. They hold the TOF detector informations,
        like the detector indices, i.e. 5 integer numbers
        (sector, module, strip, par-row and pad numbers), the
        time-of-flight and the time-over-threshold informations
        according to the test beam results.
	Each detector element can record more than one sdigit (but
        not more than 3).

  AliTOFSDigitizer
  AliTOFDigitizer:
	Base class for the (s)digitiser. AliTOFSDigitizer makes
	summable digits (AliTOFSDigit) from hits, and AliTOFDigitizer
        makes digits (quasi real data) from summable digits.

  AliTOFHitMap
	A map of (AliTOFSDigit) indices.
        The AliTOFSDigitizer uses this map to store simulation data
        (i.e. hits) before making sdigits.

  AliTOFDigitMap:
	A map of (AliTOFdigit) indices.
        The AliDDLRawData uses this map to store the TOF digits indices
        before making real digits (i.e. raw data).

  AliTOFDDLRawData:
	Base class for digit-to-raw_data transformation.
        It makes raw data from digits: practically, it transforms the
        5 detector indices (sector, module, strip, pad-row and pad numbers)
	in hardware address, consisting of 5 induces (TOF readout
        module, slot, chain, TDC and channel numbers).

  AliTOFT0:

  AliTOFTrigger:

  AliTOFQAChecker
  AliTOFQADataMakerSim


libTOFrec:
----------

Till today (February 6th 2008), it contains the following classes

  AliTOFRecoParam:

  AliTOFReconstructor:

  AliTOFcluster:
	Reconstructed point in the TOF. These objects are made
	AliTOFReconstructor. 

  AliTOFClusterFinder:

  AliTOFtrack:
	Base classe for TOF tracks. It holds ...

  AliTOFtracker
  AliTOFtrackerMI
  AliTOFtrackerV1:
        

  AliTOFpidESD:

  AliTOFQADataMakerRec:


TOF Calibration:
----------------

1. Online Calibration

1.1. New Calibration Schema

1.1.1. Configuration

The online calibration which is performed by the TOF preprocessor is 
configured according to a CDB object (stored in /TOF/Calib/Config), where
a flag for the computation of the delays is set according to the type
of data taking (cosmics ---> kFALSE / beam ---> kTRUE), and where the
starting validity of the calibration objects that will be written in the
OCDB is defined (see sec. 1.1.3.). The data are stored in the CDB object 
as entries in a TMap, with IDs "ComputingDelays" and "StartingRun"
respectively.

1.1.2. Objects

- AliTOFChannelOnlineArray: array of floats containing the delay value
  calculated for each TOF channel by the TOF preprocessor starting from
  the DAQ DA for PHYSICS runs (see TOFda.cxx). Inheriting from TObject.

- AliTOFChannelOnlineStatusArray: array of chars defining the status for each 
  TOF channel according to the processing of the data coming from PULSER and
  NOISE runs (TOFpulserda.cxx, TOFnoiseda.cxx). The status is defined also
  according to the FEE map written in the DCS FXS, where the status ON/OFF 
  of the channels is stored. The first (least significant) two bits refer to the
  FEE status, the second two to the pulser data, and the third two to the noise
  data, leaving the last two empy. The status is always (FEE/pulser/noise) 
  defined as:
  00 --> Unknown;
  01 --> Good;
  10 --> Bad.
  Inheriting from TObject.

1.1.3. OCDB

- /TOF/Calib/ParOnlineDelay: directory where the AliTOFChannelOnlineArray
  calibration objects are stored, with validity [0, 999999999], increasing the
  sv number every time. After offline calibration takes place, in case a reset 
  is needed at run XYZ, the validity changes to [XYZ, 999999999], again 
  with increasing sv. 

- /TOF/Calib/Status: directory where the AliTOFChannelOnlineStatusArray
  calibration objects are stored, with validity [current_run, 999999999]. In 
  case of a PHYSICS run, the update occurs only if the FEE map has changed. 
  In case of a PULSER/NOISE run, the update occurs once at the very end of the
  processing, so to merge the information from the FEE status map and those
  from the TOFpulserda/TOFnoiseda.

1.1.4. Reference Data

- /TOF/Calib/DAQData: directory to store the histograms at run level that 
  are produced by the TOFda. 

- /TOF/Calib/DCSData: directory to store the data that come out from the 
  processing of the TOF DCS DPs.

- /TOF/Calib/PulserData: directory to store the histograms that are produced 
  by the TOFpulserda. 

- /TOF/Calib/NoiseData: directory to store the histograms that are produced 
  by the TOFnoiseda. 

- /TOF/Calib/FEEData: directory to store the histogram reproducing the FEE
  status of the TOF channels. 

1.1.5. Usage in Reconstruction 

During reconstruction, both the AliTOFChannelOnlineArray and the 
AliTOFChannelOnlineStatusArray corresponding to the current run have to be
loaded from OCDB in the AliTOFReconstructor class instance. From there, 
they are passed to the AliTOFClusterFinder, where the status of the channel is 
used in order to decide whether to use it or not, while the delay is used to 
calibrate when the offline calibration information is not yet available. 

1.2. Old Calibration Schema

1.2.1. Configuration

No OCDB configuration entry is foreseen.

1.2.2. Objects

- AliTOFChannelOnline: object containing the value of the delay for a 
  certain TOF channel. Inheriting from TObject. An TObjArray of 157248 of such 
  objects is used to store the information coming from the TOF online 
  calibration. Inheriting from TObject.

- AliTOFChannelOnlineStatus: object containing the status of a TOF channel
  as determined during the reading of the FEE map/ during a pulser run/
  during a noise run. Three TObjArray objects of 157248 of such objects should 
  be present in the OCDB for each run: one related to the FEE status of the
  channels, one related to pulser run results, and one related to noise 
  run results. The status is defined as:
  00 --> Unknown;
  01 --> Good;
  10 --> Bad.
  Inheriting from TObject.
    
1.2.3. OCDB

- /TOF/Calib/ParOnline: directory where a TObjArray of 157248 AliTOFChannelOnline
  calibration objects are stored, with validity [0, 999999999], increasing the
  sv number every time. After offline calibration takes place, in case a reset 
  is needed at run XYZ, the validity changes to [XYZ, 999999999], again 
  with increasing sv. 

- /TOF/Calib/HW: directory where a TObjArray of 157248 AliTOFChannelOnlineStatus
  calibration objects are stored, with validity [current_run, 999999999], as 
  obtained from reading the FEE map from the DCS FXS. The update occurs only if 
  the FEE map has changed. 

- /TOF/Calib/Pulser: directory where a TObjArray of 157248 AliTOFChannelOnlineStatus
  calibration objects are stored, with validity [current_run, 999999999], as 
  obtained from a pulser run.  

- /TOF/Calib/Noise: directory where a TObjArray of 157248 AliTOFChannelOnlineStatus
  calibration objects are stored, with validity [current_run, 999999999], as 
  obtained from a noise run.  

1.2.4. Reference Data

- /TOF/Calib/DAQData: directory to store the histograms at run level that 
  are produced by the TOFda. 

- /TOF/Calib/DCSData: directory to store the data that come out from the 
  processing of the TOF DCS DPs.

- /TOF/Calib/PulserData: directory to store the histograms that are produced 
  by the TOFpulserda. 

- /TOF/Calib/NoiseData: directory to store the histograms that are produced 
  by the TOFnoiseda. 

- /TOF/Calib/FEEData: directory to store the histogram reproducing the FEE
  status of the TOF channels. 

1.2.5. Usage in Reconstruction 

During reconstruction, the TObjArray of AliTOFChannelOnline and the three
TObjArray objects of AliTOFChannelOnlineStatus coming from the FEE map, the 
pulser run data, and the noise run data corresponding to the current run have to 
be loaded from OCDB in the AliTOFReconstructor class instance. From there, 
they are passed to the AliTOFClusterFinder, where the status of the channel is 
used in order to decide whether to use it or not, while the delay is used to 
calibrate when the offline calibration information is not yet available. 

2. TOF Offline Calibration

2.1. Object

- AliTOFChannelOffline: object containing the calibration parameters for 
  each TOF channel that should correct both for the delay introduced by the
  electronics and the hardware, and for the time slewing effect. A TObjArray 
  of 157248 of such objects is stored in the CDB to perform refined calibration 
  during reconstruction. Inheriting from TObject.

2.2. OCDB

- /TOF/Calib/ParOffline: directory containing the CDB entry corresponding to the
  offline calibration of the TOF as stored in a TObjArray object of 157248
  AliTOFChannelOffline objects with validity [0, 999999999], increasing the
  sv number every time. In case a reset is needed at run XYZ, after collecting 
  the statistics necessary to the offline calibration (when the online 
  calibration object becomes valid again), the validity changes to 
  [XYZ, 999999999], again with increasing sv. 

2.3 Usage in Reconstruction

The TObjArray of 157248 AliTOFChannelOffline objects is retrieved for the current
run in AliTOFReconstructor, and passed to AliTOFClusterFinder. As soon as enough 
statistics is collected for every channel, since the validity 
of the offline calibration object was set, for each channel with a valid
status, the calibration is performed using the calibration parameters present in 
this TObjArray of AliTOFChannelOffline.

Authors:
--------

       Annalisa De Caro      <decaro@sa.infn.it>

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