ALICE FMD Off-line code

0.1

Contents

• Introduction:
• Structure:
  • libFMDbase: (see also Basic classes)
  • libFMDsim: (see also Simulation)
  • libFMDrec: (see also Reconstruction)
  • libFMDutil: (see also Utility classes.)
• Scripts (see also Scripts)
• Quick start
• Authors:

Introduction:

This file contains a short overview of the FMD code. It is by no means authoritative - only the code is good for that. However, I'll try to explain things a bit here.

Structure:

There are 4 libraries build for the FMD. These are

• libFMDbase: This contains the basic stuff, like data classes and managers.
• libFMDsim: This contains code used by the simulation only. That includes the detector class AliFMD and it's derivatives. It also contains the code for building the geometry, as well as the digitisers and raw data writer.
• libFMDrec: Code needed for the reconstruction. This include the reconstruction code itself, as well as a raw data reader.
• libFMDutil: This is a special library that contains various utility classes for the FMD expert/developer/tester. It includes code to read all data produced by the FMD, a simple event display, and code to make fake calibration and alignment data. This library is not loaded by aliroot automatically. The user has to load it herself:

        gSystem->Load("libFMDutil.so");
  

  The content of these libraries is detailed more below.

libFMDbase:

This currently (18th or March 2006) contains the classes

• AliFMDBaseDigit, AliFMDDigit, AliFMDSDigit: Base class for digits, real digits, and summable digits. The are all data classes that holds the ADC value(s) for a single strip.
• AliFMDBoolMap: A map of booleans, one for each strip.
• AliFMDUShortMap: A map of unsigned short integers, one for each strip.
• AliFMDDetector, AliFMD1, AliFMD2, AliFMD3: 3 classes that holds the parameters for each of the 3 FMD sub-detectors. These derive from AliFMDDetector, and are managed by AliFMDGeometry. Each of these also contains the translation from sensor reference frame to global reference frame.
• AliFMDRing: Parameters for the FMD rings (inner and outer type). These are managed by AliFMDGeometry.
• AliFMDGeometry: Manager of FMD geometry data. All code queries this manager for geometry parameters, so that the data is always consistent.
• AliFMDParameters: Manager of FMD parameters, like calibration parameters. This class fetches data from CDB if necessary. All code queries this manager for parameters, so that the data is always consistent.
• AliFMDCalibPedestal, AliFMDCalibGain, AliFMDCalibSampleRate, AliFMDAltroMapping: Containers of calibration parameters. These correspond to the pedestal and its width, the gain of each strip, the oversampling rate used in read-out, and the map from hardware address to detector.
• AliFMDAltroIO, AliFMDAltroReader, AliFMDAltroWriter: Low-level classes to do input/output on ALTRO formated buffers.

libFMDsim:

This currently (18th or March 2006) contains the classes

• AliFMDEdepMap: Cache of energy deposited and total number of hits for each strip. The digitiser AliFMDDigitizer uses this to store simulation data before making digits.
• AliFMDHit: A hit in the FMD active elements, as described by the simulation back-end during transport.
• AliFMD, AliFMDv0, AliFMDv1: Simulation drivers for the FMD. AliFMD is the base class. AliFMDv0 corresponds to a simulation where no hits are created, but the material distribution is right. AliFMDv1 is like AliFMDv0, except that hits are produced.
• AliFMDGeometryBuilder: Build the FMD geometry in terms of TGeo objects. The information for building the geometry is retrieved from AliFMDGeometry.
• AliFMDBaseDigitizer, AliFMDDigitizer, AliFMDSDigitizer: Base class for the digitisers. AliFMDDigitizer makes `real' digits (AliFMDDigit) from hits, and AliFMDSDigitizer makes summable digits from hits.
• AliFMDRawWriter: Writes a pseudo raw data file from the digits created by the digitisers. It uses the AliFMDAltroMapping from AliFMDParameters to make the mapping from detector coordinates to hardware addresses.

libFMDrec:

This currently (18th or March 2006) contains the classes

• AliFMDReconstructor: Reconstruct (in a naiive way) the charged particle multiplicity in the FMD strips. This also writes an AliESDFMD object to the ESD files (that class is in libESD).

• AliFMDRecPoint: Reconstructed point in the FMD. These objects are made AliFMDReconstructor.

• AliFMDRawReader: Classes to read raw data files.

libFMDutil:

This currently (18th or March 2006) contains the classes

• AliFMDInput, AliFMDInputHits, AliFMDInputDigits, AliFMDInputSDigits, AliFMDInputRecPoints: Base class, and concrete classes to read in FMD generated data. These provide a simple and unified way of getting the data. Hooks are defined to process hits, tracks, digits, and reconstructed points, as well as geometry and ESD data. See for example the scripts DrawHits.C, DrawHitsDigits.C, DrawHitsRecs.C, DrawDigitsRecs.C in the FMD/scripts sub-directory.

• AliFMDDisplay: Simple event display for FMD data, including hits, digits, reconstructed points and ESD data.

• AliFMDCalibFaker, AliFMDAlignFaker: Classes to write fake (or dummy) calibration and alignment data. These derive from TTask.

Scripts

Most scripts live in FMD/scripts. The notiable exceptions are Simulate.C, Reconstruct.C, and Config.C

Quick start

First, install ROOT. Then Install TGeant3:

    > cd ~/
    > mkdir alice
    > cd alice
    > cvs -d :pserver:cvs@root.cern.ch:/user/cvs login 
    Password: cvs
    > cvs -d :pserver:cvs@root.cern.ch:/user/cvs co geant3
    > cd geant3
    > make 
    

Now you can install AliRoot

    > cd ../
    > cvs -d :pserver:cvs@alisoft.cern.ch:/soft/cvsroot login
    Password: <empty>
    > cvs -d :pserver:cvs@alisoft.cern.ch:/soft/cvsroot co AliRoot
    > cd AliRoot
    > export ALICE_TARGET=`root-config --arch`
    > export ALICE=${HOME}/alice
    > export ALICE_ROOT=${ALICE}/AliRoot
    > export ALICE_LEVEL=new
    > export LD_LIBRARY_PATH=${ALICE_ROOT}/lib/tgt_${ALICE_TERGET}:${LD_LIBRARY_PATH}
    > export PATH=${ALICE_ROOT}/bin/tgt_${ALICE_TERGET}:${PATH}
    > export G3SYS=${ALICE}/geant3
    > make 
    

To simulate one event, do something like

    > aliroot ${ALICE_ROOT}/FMD/Simulate.C
    

To reconstruct the generated event, do

    > aliroot ${ALICE_ROOT}/FMD/Reconstruct.C
    

Now, open the file `AliESDs.root' in AliRoot, and browse through that.

Authors:

• Alla Maevskaya <Alla.Maevskaia@cern.ch>
• Christian Holm Christensen <cholm@nbi.dk>

---