<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="GENERATOR" content="Mozilla/4.51 [en] (X11; I; Linux 2.2.5-15 i686) [Netscape]">
- <title>PHOS Reconstruction Proposal</title>
-<link REL="stylesheet" href="http://www-subatech.in2p3.fr/~photons/gps_alice.css" type="text/css">
+ <title>PHOS Reconstruction in AliRoot</title>
+ <link REL="stylesheet" href="http://www-subatech.in2p3.fr/~photons/gps_alice.css" type="text/css">
</head>
<body>
-
-
-<h1>
-PHOS Reconstruction Proposal</h1>
-At the Offline meeting held during the September ALICE week, it was decided
-to make a major step in the design of the overall reconstruction framework.
-This document presents the results of our early brainstorming about the
-design of the reconstruction of the Photon Spectrometer PHOS.
-<br>
-<br>
-<p>
-<hr><a NAME="definitions and objectives"></a>
-<h1>
-Definitions and objectives</h1>
-
-<h2>
-What is PHOS ?</h2>
-We hereby consider that the PHOS detector is the <i>union</i> of two sub-detectors
-: the lead tungstate crystals and the Charged Particle Veto (CPV). Both
-sub-detectors are physically organized in <i>modules</i>. A separate document
-is dedicated to the <a href="PHOS_Proposal.html">PHOS geometry</a>.
-<h2>
-What is the reconstruction ?</h2>
-Using the AliRoot framework, we would like to be able to compare several
-CPV alternatives. The main focus will be on the photon identification capabilities
-of PHOS, i.e. on the hadron rejection capabilities.
-<p>This document describes the reconstruction software we intend to write/have
-written to achieve this objective. <i>Reconstruction</i> is meant as the
-full path from the PHOS digits to physical particles. The PHOS digits are
-obtained by the simulation part of AliRoot.
-<p>The PHOS reconstruction can be divided in three passes:
-<dl>
-<dt>
-<b>Clusterization</b></dt>
-
-<dd>
-We group adjacent crystals (pads) with a signal over a given threshold
-to form <i>clusters</i></dd>
-
-<dt>
-<b>Sub-Tracking</b></dt>
-
-<dd>
-Crystals and CPV clusters are associated to form PHOS <i>sub-tracks</i>.
-Loosely speaking, a PHOS sub-track is just a crystal cluster with an information
-on its charge.</dd>
-
-<dt>
-<b>Identification</b> (Tracking)</dt>
-
-<dd>
-Several (at least one) detector sub-tracks are combined and matched with
-<i>particles</i>.</dd>
-</dl>
-The two first passes are detector specific, i.e. do not require any information
-about other detectors. The last part may (and probably will) depend on
-other detector reconstructions.
-
-<p class="right">The key point in the following presented design is that
-we want to be able to experiment several alternatives in each of the three
-passes.
-<h2>
-Generalization</h2>
-We often tried to generalized our design 'one step up', i.e. up to the
-AliRoot framework itself, by defining pABC (pure Abstract Base Classes)
-which we derive from. This is by no mean of way of saying that this is
-the way to go. It's just a proposal, i.e. <i>a call for discussion</i>.
-Also, we tried to make an effort on the class names, but you might find
-our names strange or badly chosen. If this is the case, please <a href="mailto:aphecetc@in2p3.fr">tell
-us</a> !
-<br><!-- ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
-<hr>
-<h1>
-Clusterization</h1>
-The clusterization part of the reconstruction can be summarized by the
-following Use Case :
-<center><img SRC="usecasereconstruction.gif" ALT="[Reconstruction Use Case]" height=355 width=599></center>
-So, the basic functionalities we want here are :
-<dl>
-<dt>
-<b>Storing/Retrieving data</b></dt>
-
-<dd>
-We want to <i>read</i> digits from file, and want to be able to <i>write</i>
-clusters on file,</dd>
-
-<dt>
-<b>Clusterizing</b></dt>
-
-<dd>
-A separate document will detail the clusterization method(s).</dd>
-
-<dt>
-<b>Keeping track of what we did</b></dt>
-
-<dd>
-We would like to be able afterwards to answer questions like "I have a
-cluster in hand, with which method has it been constructed ? With which
-method parameters ?".</dd>
-</dl>
-We would like to insist on the last point. It is far more general than
-a particular PHOS issue, and must be addressed in some way by the AliRoot
-framework itself.
-<p>The following class diagram outlines the clusterization part of the
-PHOS reconstruction : a Clusterizer object groups some Digits into Clusters.
-<center><img SRC="aliphosclusterization.gif" ALT="[Clusterization Class Diagram]" ></center>
-The key point here is the possibility to actually change of clusterization
-method (Clusterizer class) at runtime. The idea is to use the <a href="http://hillside.net/patterns/">Strategy
-Design Pattern</a> (see <a href="#particle_identification">Particle Identification</a>
-for a class diagram).
-<p>The following tables presents a trial CRC study of the PHOS classes
-related to the clusterization that lead to the above class diagram.
-<br><!-- crc template
-<div class="crc">
-<dl>
-<dt><strong>Classname:</strong>
-<dd><em class="classname">Ali</em>
-<dt><strong>Superclasses :</strong>
-<dd>Ali
-<dt><strong>Subclasses :</strong>
-<dd>Ali
-<dt><strong>Responsabilities: </strong>
-<dd>
-<dt><strong>Collaborators: </strong>
-<dd>Ali
-</dl>
-</div>
--->
-<hr class="small-separation">
-<div class="crc">
-<dl>
-<dt>
-<b>Classname:</b></dt>
-
-<dd>
-<i>AliPHOSDigit</i></dd>
-
-<dt>
-<b>Superclasses :</b></dt>
-
-<dd>
-AliDigit</dd>
-
-<dt>
-<b>Subclasses :</b></dt>
-
-<dd>
-AliPHOSCrystalDigit, AliPHOSCPVDigit</dd>
-
-<dt>
-<b>Responsabilities:</b></dt>
-
-<dd>
-Base class for the storage of PHOS digits. Must identify digits (module,row,column)
-and give access to the corresponding signal (energy).
-<br>It can be added to an AliPHOSCluster.</dd>
-<dt>
-<b>Collaborators:</b></dt>
-
-<dd>
-AliPHOSCluster</dd>
-</dl>
-</div>
-
-<hr class="small-separation">
-<div class="crc">
-<dl>
-<dt>
-<b>Classname:</b></dt>
-
-<dd>
-<i>AliPHOSCluster</i></dd>
-
-<dt>
-<b>Superclasses :</b></dt>
-
-<dd>
-AliCluster (?)</dd>
-
-<dt>
-<b>Subclasses :</b></dt>
-
-<dd>
-AliPHOSCrystalCluster, AliPHOSCPVCluster</dd>
-
-<dt>
-<b>Responsabilities:</b></dt>
-
-<dd>
-Base class for PHOS Xtal/CPV clusters. A cluster must know its module,
-its spatial position, must be able to add digits to itself and to give
-access to (/iterates on) its digits.</dd>
-
-<dt>
-<b>Collaborators:</b></dt>
-
-<dd>
-AliPHOSDigit, AliPHOSGeometry</dd>
-</dl>
-</div>
-
-<hr class="small-separation">
-<div class="crc">
-<dl>
-<dt>
-<b>Classname:</b></dt>
-
-<dd>
-<i>AliPHOSGeometry</i></dd>
-
-<dt>
-<b>Superclasses :</b></dt>
-
-<dd>
-none</dd>
-
-<dt>
-<b>Subclasses :</b></dt>
-
-<dd>
-none</dd>
-
-<dt>
-<b>Responsabilities:</b></dt>
-
-<dd>
-Handles several PHOS Xtal/CPV geometrical characteristics (sizes, positions,
-etc...).
-<br>This class is a <b>Singleton</b>.
-</dd>
-<dt>
-<b>Collaborators:</b></dt>
-
-<dd>
-AliPHOS*Cluster, AliPHOSClusterizer*</dd>
-</dl>
-</div>
-
-<hr class="small-separation">
-<div class="crc">
-<dl>
-<dt>
-<b>Classname:</b></dt>
-
-<dd>
-<i>AliPHOSClusterizer*</i></dd>
-
-<dt>
-<b>Superclasses :</b></dt>
-
-<dd>
-AliClusterizer</dd>
-
-<dt>
-<b>Subclasses :</b></dt>
-
-<dd>
-none</dd>
-
-<dt>
-<b>Responsabilities:</b></dt>
-
-<dd>
-Concrete class(es) which implements the makeClusters method. From a list
-of Ali(PHOS)Digit, this method must compute a list of Ali(PHOS)Cluster.</dd>
-
-<dt>
-<b>Collaborators:</b></dt>
-
-<dd>
-AliPHOS*Digit, AliPHOS*Cluster</dd>
-</dl>
-</div>
-
-<div class="crc">
-<dl>
-<dt>
-<b>Classname:</b></dt>
-
-<dd>
-<i>AliParameter</i></dd>
-
-<dt>
-<b>Superclasses :</b></dt>
-
-<dd>
-none</dd>
-
-<dt>
-<b>Subclasses :</b></dt>
-
-<dd>
-(?) probably many of them</dd>
-
-<dt>
-<b>Responsabilities:</b></dt>
-
-<dd>
-pABC. Keep track of methods used and method parameters used. What should
-be the basic interface for this ???</dd>
-
-<dt>
-<b>Collaborators:</b></dt>
-
-<dd>
-Many classes...</dd>
-</dl>
-</div>
-<!-- +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
-<hr><a NAME="sub_tracking"></a>
-<h1>
-Sub-Tracking</h1>
-Once we have crystal and CPV clusters, we must associate them to make what
-we would like to call SubTracks. Doing sub-tracks from clusters is, from
-the design point of view, much like going from digits to clusters. We should
-be able to easily change the class which actually do the sub-tracking job
-:
-<center><img SRC="aliphossubtracking.gif" ALT="[SubTracking Class Diagram]"></center>
-
-<div class="crc">
-<dl>
-<dt>
-<b>Classname:</b></dt>
-
-<dd>
-<i>AliPHOSSubTrack</i></dd>
-
-<dt>
-<b>Superclasses :</b></dt>
-
-<dd>
-AliSubTrack (?)</dd>
-
-<dt>
-<b>Subclasses :</b></dt>
-
-<dd>
-none</dd>
-
-<dt>
-<b>Responsabilities:</b></dt>
-
-<dd>
-Concrete storage class for a PHOS subtrack. It must be able to give access
-to its clusters, and to identify itself as being part of PHOS.</dd>
-
-<dt>
-<b>Collaborators:</b></dt>
-
-<dd>
-AliPHOSSubTracker*</dd>
-</dl>
-</div>
-
-<hr class="small-separation">
-<div class="crc">
-<dl>
-<dt>
-<b>Classname:</b></dt>
-
-<dd>
-<i>AliPHOSSubTracker*</i></dd>
-
-<dt>
-<b>Superclasses :</b></dt>
-
-<dd>
-AliSubTracker</dd>
-
-<dt>
-<b>Subclasses :</b></dt>
-
-<dd>
-none</dd>
-
-<dt>
-<b>Responsabilities:</b></dt>
-
-<dd>
-Concrete class(es) which implements the makeSubTracks method. From a list
-of Ali(PHOS)Cluster, this method must compute a list of Ali(PHOS)SubTrack.</dd>
-
-<dt>
-<b>Collaborators:</b></dt>
-
-<dd>
-AliPHOSCluster, AliPHOSSubTrack</dd>
-</dl>
-</div>
-<!-- ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
-<hr><a NAME="particle_identification"></a>
-<h1>
-Particle Identification</h1>
-Clusterization and subtracking are two activities that are <i>detector-driven</i>.
-We can indeed imagine that the full ALICE reconstruction could be (pseudo-)coded
-in AliRoot like :
-<pre class="code">for each detector in ALICE do {
- detector->Reconstruction() ;
-}</pre>
-assuming that each detector provides a Reconstruction method, and that
-there's a way to parametrize each detector's behavior. The latter could
-be done in the initialization phase of AliRoot, e.g. in the <tt>Config.C</tt>
-file :
-<pre class="code"><i>// Create PHOS clusterizers
-</i>AliPHOSCrystalClusterizerV1 aXtalClusterizer(...) ;
-AliPHOSCPVClusterizerV3 aCPVClusterizer(...) ;
-<i>// Create PHOS SubTracker
-</i>AliPHOSSubTrackerV0 aPHOSSubTracker(...) ;
-<i>// Create a PHOS Reconstructioner
-</i>AliPHOSReconstructioner aPHOSReconstructioner(aXtalClusterizer,
- aCPVClusterizer,
- aPHOSSubTracker) ;
-
-<i>// Create PHOS detector and associate
- a reconstructioner with it
-</i>AliPHOS* phos = new AliPHOSVxx("PHOS",
- "PHOS Version xx",
- &;aPHOSReconstructioner) ;</pre>
-In the above code, the clusterization strategies (for Xtals and CPV) and
-the sub-tracking strategy are managed by a control class AliPHOSReconstrutioner
-which would derive from a pABC AliReconstructioner.
-<center><img SRC="aliphosreconstructioner.gif" ALT="[Reconstruction Class Diagram]" height=312 width=484></center>
-The <tt>detector->Reconstruction()</tt> method would then only delegate
-its job to the selected Reconstructioner (aPHOSReconstructioner in the
-above example).
-<p>If we now turn to the particle identification problem, two cases must
-be considered :
-<dl>
-<dt>
-<b>Standalone PHOS</b></dt>
-
-<dd>
-The particle identification is just a refinement (e.g. computation of some
-new values to cut upon) of subtracking. We only need to access PHOS SubTracks.</dd>
-
-<dt>
-<b>PHOS + other ALICE sub-systems</b></dt>
-
-<dd>
-In this case, we must associate several subtracks, coming from different
-sub-systems, in order to identify particles. One problem to solve is how
-to access other sub-systems SubTracks.</dd>
-</dl>
-For this stage of the analysis, the AliRoot activity can not be detector-driven
-anymore. Instead we would like to propose this activity to be <i>particle
-hunting driven</i>. For example :
-<pre class="code"><i>// we assume that all detectors have produced their subtracks in the event event_number
-</i>AliParticleHunter* aPhotonFinder = new AliPhotonFinder(...) ;
-
-<i>/* the UseDetector("ADET") method should "connect"
- the ParticleHunter with the ADET subtrack branch so it can access
- other detectors subtracks.
- We assume that a subtrack knows in which detector she is, so we
- can recover this information later (e.g. in the FindParticles method).
-*/
-
-</i>aPhotonFinder->UseDetector("ITS") ;
-aPhotonFinder->UseDetector("TPC") ;
-aPhotonFinder->UseDetector("PHOS") ;
-
-for each event do {
- aPhotonFinder->FetchSubTracks(event) ;
- <i>/* The FindParticle method can now plays
- with all the ITS,TPC and PHOS subtracks... */
-</i> aPhotonFinder->FindParticles() ;
-}</pre>
-
-<center><img SRC="classes_identification.gif" ALT="[Identification Class Diagram]" height=279 width=480></center>
-
-<div class="crc">
-<dl>
-<dt>
-<b>Classname:</b></dt>
-
-<dd>
-<i>AliPHOSReconstructioner*</i></dd>
-
-<dt>
-<b>Superclasses :</b></dt>
-
-<dd>
-AliReconstructioner (?)</dd>
-
-<dt>
-<b>Subclasses :</b></dt>
-
-<dd>
-none</dd>
-
-<dt>
-<b>Responsabilities:</b></dt>
-
-<dd>
-This class is control class for the clusterizations and the subtracking.
-It must handles the clusters and subtracks IO. It can be "added" to the
-AliPHOS detector.</dd>
-
-<dt>
-<b>Collaborators:</b></dt>
-
-<dd>
-AliPHOSClusterizer, AliPHOSSubTracker, AliPHOS</dd>
-</dl>
-</div>
-
-<div class="crc">
-<dl>
-<dt>
-<b>Classname:</b></dt>
-
-<dd>
-<i>AliParticleHunter</i></dd>
-
-<dt>
-<b>Superclasses :</b></dt>
-
-<dd>
-non</dd>
-
-<dt>
-<b>Subclasses :</b></dt>
-
-<dd>
-AliPhotonFinder</dd>
-
-<dt>
-<b>Responsabilities:</b></dt>
-
-<dd>
-Associate a number (1..n) different detector subtracks to identify particles.
-It must be able to fetch subtracks for a number of different detectors.
-It handle IO of produced particles.</dd>
-
-<dt>
-<b>Collaborators:</b></dt>
-
-<dd>
-AliSubTrack, AliParticle, AliDetector</dd>
-</dl>
-</div>
-<!-- ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
-<hr>
-<h1>
-Disk Storage Structure</h1>
-We present in this section how the PHOS reconstructed data will be arranged
-on disk.
-<p>We suppose that there is one TreeR (Reconstruction Tree) per event,
-and we store different kinds of objects in differents branches, i.e. the
-<b>PHOSCPVClusters
-branch</b> contains CPV clusters the <b>PHOSCrystalClusters branch</b>
-contains Crystal clusters, the <b>PHOSSubTracks branch</b> contains PHOS
-SubTracks, and the <b>PHOSParameters branch</b> contains several information
-related to the way Clusters and SubTracks were made. The following figure
-indicates the inter-relation(s) between those branches and the relation
-between those branches and the PHOS branch in the Digit Tree.
-<center><img SRC="TreeR.gif" ALT="[Reconstruction Tree Structure]" height=425 width=483></center>
-
-<h2>
-How are the links implemented ?</h2>
-If we assume that all the above branches are implemented using <a href="http://root.cern.ch/root/html/TClonesArray.html">TClonesArray</a>,
-we could index things using simple integers refering to positions in the
-TClonesArray. For example, a cluster will keep track of its digits by recording
-the list of the digits position in the TClonesArray of the PHOS branch
-in the digit tree. These positions are of course only valid within a given
-event.
-<p>If we want to be less implementation dependant we could probably have
-classes such as <i>AliDigitIdentifier</i> (which could then be anything
-we like, e.g. a simple integer wrapper or a set {event_number, index position}).
-This solution could be more disk-space consuming, but would have the tremendous
-advantage to isolate "logical" references from implementation.
-<h2>
-What should we save ?</h2>
-At least in the beginning of the analysis, we should be able to perform
-the reconstruction step by step, i.e. be able to save clusters, subtracks
-and particles. It would be nice to include a switching mechanism to e.g.
-disconnect the cluster output if we want to save disk space for instance. <!-- +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
-<hr><a NAME="parameters"></a>
-<h1>
-Keeping the entropy small</h1>
-We come back to the problem stated in the clusterization section about
-'keeping track of what we did'. We don't want to loose too much information
-along our way from the raw data to the particles so we can have some checkpoints.
-<p>We proposed in the above class diagrams to use a generic <tt>AliParameter</tt>
-class which could answer question such as 'what was the sub-tracker method
-and version used to do this sub-track ?' or 'what was the Xtal clustering
-low threshold ?'. This 'AliParameter' could be accessible through methods
-like <tt>AliParameter& AliCluster::GetMakerInformation</tt>. That's
-all nice, but we say nothing about what this AliParameter class is.
-<p>We could imagine a very simple AliParameter implementation using e.g.
-(parameter_name, parameter_value) pairs encapsulated in such an AliParameter
-class. Or, entering fully the Alice Wonderland, we could dream of a much
-more ambitious generic parameter class, in which the actual storage of
-the parameters in done using <a href="http://www.w3.org">XML</a> (the W3
-eXtensible Markup Language). The base AliParameter would then only provide
-basic interface to code/decode XML tags, and each subsystems would provide
-DTD to describes their parameters, which would then ressemble 'parameters
-sheets'. We can imagine DTDs per detector or per domain (geometry, reconstruction,
-physics analysis...).
-<br>The strenght of this approach is the use of a (new) <b>standard</b>
-in which data are represented in structured ASCII files. ASCII files are
-human readable/produceable, easy to exchange between computers, and many
-tools already exists, in a wide variety of languages (C/C++, Java, Perl,
-Python...), to handles XML compliant files.
-<p>But, well, may be this is only a dream... and too much work for our
-purposes. Anyway, comments on this idea are welcome ! More information
-can be found at <a href="http://www.oasis-open.org/cover/">http://www.oasis-open.org/cover/</a>
-<br><!-- +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -->
-<hr>
-<h1>
-Summary</h1>
-To perform the PHOS reconstruction, we need/propose the following classes
-:
-<h2>
-New classes</h2>
-
-<dl>
-<dt>
-<b>Ali(PHOS)Cluster</b></dt>
-
-<dd>
-(pABC) Storage class for groups of digits (per detector)</dd>
-
-<dt>
-<b>Ali(PHOS)SubTrack</b></dt>
-
-<dd>
-(pABC) Storage class for groups of clusters (per detector)</dd>
-
-<dt>
-<b>Ali(PHOS)Reconstructioner</b></dt>
-
-<dd>
-(pABC) Control class for clusterization and subtracking.</dd>
-
-<dt>
-<b>AliParticleHunter</b></dt>
-
-<dd>
-(pABC) Working class to associate different subtracks into particles.</dd>
-
-<dt>
-<b>AliParticle</b></dt>
-
-<dd>
-(pABC?) Storage class for particles.</dd>
-
-<dt>
-<b>AliParameter</b></dt>
-
-<dd>
-(pABC!) Entropy minimizing class. Keeps track of methods/parameters used
-to make clusters, subtracks and particles.</dd>
-
-<dt>
-<b>Ali(Digit,Cluster,SubTrack)Identifier</b></dt>
-
-<dd>
-A simple integer wrapper or a more elaborated way of indexing reconstruction
-objects, so we can go one step back at every analysis step (e.g. access
-the list of clusters a subtrack is made of).</dd>
-</dl>
-
-<h2>
-AliRoot classes impacted</h2>
-
-<dl>
-<dt>
-<b>AliRun</b></dt>
-
-<dd>
-Add Reconstruction method, which would delegate to the corresponding Reconstruction
-methods of the different detectors.</dd>
-
-<dt>
-<b>AliDetector</b></dt>
-
-<dd>
-Add GetSubTracks method (returning a list of subtracks for a given event),
-and Reconstruction method (which delegates its jobs to an AliReconstructioner
-object, selectable at runtime).</dd>
-</dl>
-
+ <h1>
+ PHOS Reconstruction
+ </h1>
+ <hr><hr>
+ <ul>
+ <li>
+ <a href="reconstruction.html#Definitions and objectives">Definitions and objectives</a>
+ <ul>
+ <li>
+ <a href="reconstruction.html#What is PHOS">What is PHOS ?</a>
+ </li>
+ <li>
+ <a href="reconstruction.html#Reconstruction design">Reconstruction design</a>
+ </li>
+ <li>
+ <a href="reconstruction.html#How to use it">How to use it</a>
+ </li>
+ </ul>
+ <li>
+ <a href="reconstruction.html#Clusterization">Clusterization</a>
+ </li>
+ <li>
+ <a href="reconstruction.html#Sub-Track construction">Sub-Track construction</a>
+ </li>
+ <li>
+ <a href="reconstruction.html#Particle identification">Particle identification</a>
+ </li>
+ <li>
+ <a href="reconstruction.html#Disk Storage Structure">Disk Storage Structure</a>
+ </li>
+ <li>
+ <a href="reconstruction.html#How are the links implemented">How are the links implemented</a>
+ </li>
+ </ul>
+ <a NAME="Definitions and objectives"></a>
+ <hr><hr>
+ <h1>
+ Definitions and objectives
+ </h1>
+ <a NAME="What is PHOS"></a> <h2>
+ What is PHOS ?
+ </h2>
+ PHOS is the association of two sub-detectors:
+ <ul>
+ <li>
+ the lead-tungstate crystals electromagnetic-calorimeter named <b>EMCA</b>,
+ </li>
+ <li>
+ and a pre-shower gas detector named <b>PPSD</b>.
+ </li>
+ </ul>
+ Both sub-detectors are physically organized in <i>modules</i>. A separate document
+ is dedicated to the description of the <a href="simulation.html">PHOS geometry</a>.
+ <a NAME="Reconstruction design"></a>
+ <h2>
+ Reconstruction design
+ </h2>
+ The reconstruction software consists in making <a href="html/AliPHOSRecParticle.html">particles</a>
+ from the <a href="html/AliPHOSDigit.html">digits</a> generated by the <a href="simulation.html">simulation</a>.
+ <p>
+ <center>
+ <a href="images/phosreconstructs.eps">
+ <img src="images/phosreconstructs.gif" alt="Use Case of reconstruction" width=800>
+ </a>
+ <p>
+ <b> Figure 1.: </b> <i>Use Case for reconstruction. Only PHOS is implemented. Other detectors are ignored.
+ Click on image for full scale</i>
+ </center>
+ The PHOS reconstruction is delegated by the <a href="html/AliPHOSv0.html">detector</a> to a
+ <a href="html/AliPHOSReconstructioner.html">reconstructioner</a> algorithmic object. It proceeds along three steps:
+ <dl>
+ <dt>
+ <b>Clusterization</b>
+ </dt>
+ <dd>
+ The reconstruction of the showers (total energy loss and incident direction)
+ induced in the EM calorimeter (<a href="html/AliPHOSEmcRecPoint.html">AliPHOSEmcRecPoint</a>)
+ and of the pads hit in the pre-shower detector (<a href="html/AliPHOSPpsdRecPoint.html" >AliPHOSPpsdRecPoint</a>).
+ The clustering is delegated to the algorithmic object <a href="html/AliPHOSClusterizerv1.html">AliPHOSClusterizerv1</a>
+ which derives from the interface <a href="html/AliPHOSClusterizer.html">AliPHOSClusterizer</a>. The clusterization is controlled
+ by several parameters.
+ </dd>
+ <dt>
+ <b>Sub-Track construction</b>
+ </dt>
+ <dd>
+ Sub tracks are obtained by combining reconstructed points in EMCA and PPSD to form a track segment
+ (<a href="html/AliPHOSTrackSegment.html">AliPHOSTrackSegment</a>). This construction is delegated to the
+ algorithmic object <a href="html/AliPHOSTrackSegmentMakerv1.html">AliPHOSTrackSegmentMakerv1</a>
+ which derives from the interface <a href="html/AliPHOSTrackSegmentMaker.html">AliPHOSTrackSegmentMaker</a>.
+ </dd>
+ <dt>
+ <b>Particle identification</b>
+ </dt>
+ <dd>
+ From each track segment a reconstructed particle (<a href="html/AliPHOSRecParticle.html">AliPHOSRecParticle</a>)
+ is made the identification being based on the information delivered by the PPSD (which PPSD stage is hit)
+ and by EMCA (shower profile and topology).The identification is delegated to the
+ algorithmic object <a href="html/AliPHOSPIDv1.html">AliPHOSPIDv1</a>
+ which derives from the interface <a href="html/AliPHOSPID.html">AliPHOSPID</a>. Several parameters control the identification
+ procedure.
+ </dd>
+ </dl>
+ The first step is detector specific, i.e. does not require any information
+ about other detectors. The two last steps may (and probably will) depend on
+ other detector reconstructions (connecting sub tracks or combining particle identification delivered by
+ various sub-detectors).
+ <a NAME="How to use it"></a>
+ <h2>
+ How to use it ?
+ </h2>
+ This is a little piece of code which shows how to use the reconstruction. It can be used in a Root macro or the class
+ <a href="html/AliPHOSAnalyze.html">AliPHOSAnalyze</a> can be used instead together with the GUI interface
+ <a href="EditorBar.C">EditorBar.C</a>:
+ <pre class="code">
+ fRootFile = new TFile("MyFileName", "update") ; // open the root file created by the simulation
+ gAlice = (AliRun*) fRootFile->Get("gAlice"); // get from file the AliRun object
+ fPHOS = (AliPHOSv0 *)gAlice->GetDetector("PHOS") ; // get from file the detector object
+ fGeom = AliPHOSGeometry::GetInstance( // get the geometry used for the simulation
+ fPHOS->GetGeometry()->GetName(),
+ fPHOS->GetGeometry()->GetTitle() ) ;
+
+ //========== Initializes the Index to Object converter
+ fObjGetter = AliPHOSIndexToObject::GetInstance(fPHOS) ;
+
+ //========== Create the Clusterizer and set a few parameters
+ fClu = new AliPHOSClusterizerv1() ;
+ fClu->SetEmcEnergyThreshold(0.030) ;
+ fClu->SetEmcClusteringThreshold(1.0) ;
+ fClu->SetPpsdEnergyThreshold (0.0000002) ;
+ fClu->SetPpsdClusteringThreshold(0.0000001) ;
+ fClu->SetLocalMaxCut(0.03) ;
+ fClu->SetCalibrationParameters(0., 0.00000001) ;
+ cout << "AnalyzeOneEvent > using clusterizer " << fClu->GetName() << endl ;
+ fClu->PrintParameters() ;
+
+ //========== Creates the track segment maker
+ fTrs = new AliPHOSTrackSegmentMakerv1() ;
+ cout << "AnalyzeOneEvent > using tack segment maker " << fTrs->GetName() << endl ;
+ fTrs->UnsetUnfoldFlag() ;
+
+ //========== Creates the particle identifier
+ fPID = new AliPHOSPIDv1() ;
+ cout << "AnalyzeOneEvent > using particle identifier " << fPID->GetName() << endl ;
+ fPID->SetShowerProfileCuts(0., 0., 0., 0.) ;
+ fPIS->SetDispersionCutOff(0.34) ;
+
+ //========== Creates the Reconstructioner
+ fRec = new AliPHOSReconstructioner(fClu, fTrs, fPID) ;
+
+ //=========== Connect the various Tree's for evt
+ gAlice->GetEvent(evt);
+
+ //=========== Fill the fDigits array from the Digit TTree
+ gAlice->TreeD()->GetEvent(0) ;
+
+ //=========== Do the reconstruction
+ fPHOS->Reconstruction(fRec);
+
+ // =========== Write to the root file
+ fRootFile->Close() ;
+ </pre>
+ <hr>
+ <a NAME="Clusterization"></a>
+ <h1>
+ <a href="html/AliPHOSClusterizerv1.html">Clusterization</a>
+ </h1>
+ A <a href="html/AliPHOSDigit.html">digit</a> is a set of two numbers: the id of the elementary cell
+ numbered from 1 to the maximum number of cells (EMCA+PPSD), and a digitized deposited energy. With
+ the help of the <a href="html/AliPHOSGeometry.html">geometry</a> object the absolute id is converted into
+ a relative numbering with a single EMCA or PPSD module, in terms of rows and columns
+ ( <i>ALIPHOSGeometry::AbsToRelNumbering()</i> ). A clustering algorithm ( <i> AliPHOSClusterizerv1::MakeClusters()</i> )
+ groups neighbouring cells in EMCA and PPSD ( <i>AliPHOSClusterizerv1::AreNeighbours()</i> ) where two cells
+ are defined as neighbours if they have a common edge or a common corner. The algorithm is controlled with
+ alltogether 4 parameters:
+ <ul>
+ <li> the energy thresholds (one for EMCA, <i>fEmcEnergyThreshold</i> and one for PPSD, <i> fPpsdEnergyThreshold</i>)
+ which the deposited energy of the digits must surpass to be taken into account for the clusterization;
+ </li>
+ <li> the energy thresholds (one for EMCA, <i>fEmcEnergyThreshold</i> and one for PPSD, <i>fPpsdEnergyThreshold</i>)
+ which the deposited energy of the digits must surpass to start a cluster.
+ </li>
+ </ul>
+ An ensemble of neighbouring digits is called a reconstructed point. The PHOS clusterizer produces
+ <a href="html/AliPHOSEmcRecPoint.html">EmcRecPoints</a> and <a href="html/AliPHOSPpsdRecPoint.html">PpsdRecPoints</a>
+ deriving form the base class <a href="html/AliPHOSRecPoint.html">AliPHOSRecPoint</a>. Each reconstructed point
+ points, through a mechanism described later, to the digits at its origin. Since a digit remembers which
+ primary particle(s) were at its origin, the list of primary particles at the origin of a reconstructed
+ point is provided by the method <i>AliPHOSRecPoint::GetPrimaries()</i>).
+ <p>
+ The reconstructed points are contained in two <a href="http://root.cern.ch/root/html/TObjArray.html">TObjArray</a>
+ (mandatory because the size of a reconstructed
+ point depends on the number of digits used to build it) which are stored in <i>TreeR</i>, branch <i>PHOSEmcRP</i>
+ for EMCA and branch <i>PHOSPpsdRP</i> for PPSD.
+ </p>
+ <hr>
+ <a NAME="Sub-Track construction"></a>
+ <h1>
+ <a href="html/AliPHOSTrackSegmentMakerv1.html">Track Segments Maker</a>
+ </h1>
+ Each EMCA reconstructed point is either combined with one or two PPSD reconstructed points to form
+ a <a href="html/AliPHOSTrackSegment.html">track segment</a> or constitutes a track segment by itself. As a first step
+ the EMCA reconstructed points are unfolded in case there is more than one local maximum ( overlapping
+ showers) to make two new reconstructed points which digit's energy is shared after a fitting procedure.
+ The unfolding procedure can be switch on and off with the method: <i>AliPHOSTrackSegmentMakerv1::(Un)SetUnfoldFlag()</i>.
+ EMCA reconstructed points and PPSD reconstructed points are then linked together to form pairs or triplets
+ according to their relative distance. Each track segment points is linked, through a mechanism described later, to the
+ reconstructed points at its origin.
+ <p>
+ The track segments are contained in a <a href="http://root.cern.ch/root/html/TClonesArray.html">TClonesArray</a> which are stored in <i>TreeR</i>, branch <i>PHOSTS</i>.
+ </p>
+ <hr>
+ <a NAME="Particle identification"></a>
+ <h1>
+ <a href="html/AliPHOSPIDv1.html">Particle Identification</a>
+ </h1>
+ Clusterization and track segments making are two activities that are <i>detector-driven</i>. This is not the case for the
+ particle identification. Indeed a particle might be identified by combining the track segments calculated by several
+ detectors. Up to know the implementation for such a mechanism is not yet done. Instead PHOS has its own stand alone
+ particle identification algorithm which associates a <a href="html/AliPHOSRecParticle.html">reconstructed particle</a> to
+ each track segment. The particle identification is controlled by several parameters which can be set by the user. Each
+ reconstructed particle is linked, through a mechanism described later, to the track segment at its origin.
+ The various types of reconstructed particles are the following:
+ <table>
+ <tr>
+ <td><b>NEUTRAL</b>: </td>
+ <td>a reconstructed point in EMCA, none in the two layers of the PPSD;</td>
+ </tr>
+ <tr>
+ <td><b>GAMMA</b> : </td>
+ <td>a reconstructed point in the lower PPSD layer, none in the upper one, and a reconstructed point in
+ EMCA that satisfies the shower topology cuts;</td>
+ </tr>
+ <tr>
+ <td><b>GAMMAHADRON</b> : </td>
+ <td>as a GAMMA, but the EMCA reconstructed point does not satisfy the shower topology cuts;</td>
+ </tr>
+ <tr>
+ <td><b>CHARGED</b>: </td>
+ <td>a reconstructed point in EMCA, and one in the upper layer of the PPSD;</td>
+ </tr>
+ <tr>
+ <td><b>NEUTRALEM</b>: </td>
+ <td>a NEUTRAL particle for which the EMCA reconstructed point satisfies the shower profile cut;</td>
+ </tr>
+ <tr>
+ <td><b>NEUTRALHADRON</b>:</td>
+ <td> a NEUTRAL particle for which the EMCA reconstructed point does not satisfy the shower profile cut;</td>
+ </tr>
+ <tr>
+ <td><b>ELECTRON</b>: </td>
+ <td>a CHARGED particle for which the EMCA reconstructed point satisfies the shower profile cut;</td>
+ </tr>
+ <tr>
+ <td><b>CHARGEDHADRON</b>:</td>
+ <td> a CHARGED particle for which the EMCA reconstructed point does not satisfy the shower profile cut;</td>
+ </tr>
+ </table>
+ <hr>
+ <a NAME="Disk Storage Structure"></a>
+ <h1>
+ Disk Storage Structure
+ </h1>
+ All the three types of reconstructed objects( reconstructed point, track segment and reconstructed particle) are stored in
+ the reconstruction Tree (<i>TreeR</i>). The container of the reconstructed points is a
+ <a href="http://root.cern.ch/root/html/TObjArray.html">TObjArray</a> and the container
+ of the track segment and the reconstructed particles is a
+ <a href="http://root.cern.ch/root/html/TClonesArray.html">TClonesArray</a>. The names of the branches are respectively:
+ PHOSEmcRP, PHOSPpsdRP, PHOSTS and PHOSRP. The <i>TreeR</i> is best seen in the following example:
+ <pre class="code">
+ root [2] TFile myfile("junk.root")
+ root [3] TTree * reconstructedtree = (TTree *)myfile.Get("TreeR0")
+ root [5] reconstructedtree.Print()
+ ******************************************************************************
+ *Tree :TreeR0 : Reconstruction *
+ *Entries : 1 : Total Size = 10882 bytes File Size = 4024 *
+ * : : Tree compression factor = 5.65 *
+ ******************************************************************************
+ *Branch :PHOSEmcRP : PHOSEmcRP *
+ *Entries : 1 : Total Size = 0 bytes File Size = 0 *
+ *Baskets : 0 : Basket Size = 16000 bytes Compression= 1.00 *
+ *............................................................................*
+ *Branch :PHOSPpsdRP : PHOSPpsdRP *
+ *Entries : 1 : Total Size = 8334 bytes File Size = 1476 *
+ *Baskets : 1 : Basket Size = 16000 bytes Compression= 5.65 *
+ *............................................................................*
+ *Branch :PHOSTS : PHOSTS *
+ *Entries : 1 : Total Size = 0 bytes File Size = 0 *
+ *Baskets : 0 : Basket Size = 16000 bytes Compression= 1.00 *
+ *............................................................................*
+ *Branch :PHOSRP : PHOSRP *
+ *Entries : 1 : Total Size = 0 bytes File Size = 0 *
+ *Entries : 1 : Total Size = 0 bytes File Size = 0 *
+ *Baskets : 0 : Basket Size = 16000 bytes Compression= 1.00 *
+ *............................................................................*
+ root [6]
+ </pre>
+ <center>
+ <img src="images/BranchesInTreeR.gif" alt="branches in reconstructed Tree">
+ <p>
+ <b>Figure 2: </b><i>Branches in TreeR generated by the PHOS reconstruction.
+ PHOSEmc(Ppsd)RP contains EMCA(PPSD) reconstructed points in
+ <a href="http://root.cern.ch/root/html/TObjArray.html">TObjArray</a>;
+ PHOSTS contains track segments in a
+ <a href="http://root.cern.ch/root/html/TClonesArray.html">TClonesArray</a>; PHOSRP contains reconstructed
+ particles in a <a href="http://root.cern.ch/root/html/TClonesArray.html">TClonesArray</a>. </i>
+ </p>
+ </center>
+ <hr>
+ <a NAME="How are the links implemented"></a>
+ <h1>
+ How are the links implemented ?
+ </h1>
+ An algorithmic class, <a href="html/AliPHOSIndexToObject.html">AliPHOSIndexToObject</a> returns a pointer to the object of
+ interest given the index of its storage in the array
+ (<a href="http://root.cern.ch/root/html/TObjArray.html">TObjArray</a> or
+ <a href="http://root.cern.ch/root/html/TClonesArray.html">TClonesArray</a>). It is a singleton (only one instance of the
+ object does exist at run time). It must be initialized once:
+ <pre class="code">
+ AliPHOS * phos = (AliPHOSv0 *)gAlice->GetDetector("PHOS") ;
+ AliPHOSIndexToObject::GetInstance(phos) ;
+ </pre>
+ It can then be used as follow, for example for retrieving a particle from the kine tree (<i>TreeK</i>):
+ <pre class="code">
+ AliPHOSIndexToObject * please = AliPHOSIndexToObject::GetInstance() ;
+ Int_t index = 123 ;
+ TParticle * primaryparticle = please->GimePrimaryParticle(index) ;
+ </pre>
+ We shall now detail how the various reconstruction objects are linked together.
+ <h4>
+ Digits to primary particles
+ </h4>
+ <A href="html/AliPHOSDigit.html">Digits</a> have three additional data members (<i>fPrimary1(2,3)</i>) that gives the index
+ of the primary particles (maximum 3) that have contributed to the formation of the digit. Remember that in PHOS a digit is
+ obtained from all the hits accumulated in a single cell.
+ This is not really elegant, but because the container of digits is a
+ <a href="http://root.cern.ch/root/html/TClonesArray.html">TClonesArray</a> it is not possible
+ to replace the three data members by an array of integers of variable length as all objects in a
+ <a href="http://root.cern.ch/root/html/TClonesArray.html">TClonesArray</a> must be identical. To retrieve the particles that
+ have contibuted to a digit, do:
+ <pre class="code">
+ // initialization
+ // open root file
+ TFile rootfile("junk.root") ;
+ // get AliRun object
+ gAlice = (AliRun *)rootfile.Get("gAlice") ;
+ // get detector object
+ AliPHOSv0 * phos = (AliPHOSv0 *)gAlice->GetDetector("PHOS") ;
+ // get the geometry associated with the detector
+ AliPHOSGeometry::GetInstance( phos->GetGeometry()->GetName(), phos->GetGeometry()->GetTitle() ) ;
+ // initializes the index to object converter
+ AliPHOSIndexToObject::GetInstance(phos) ;
+ // get the list of digits
+ TClonesArray * digitslist = phos->Digits() ;
+ // loop over the list of digits
+ TIter nextdigit(digitslist) ;
+ AliPHOSDigit * digit ;
+ TParticle * primaryparticle[3] ;
+ // get the pointer of the index to object converter
+ AliPHOSIndexToObject * please = AliPHOSIndexToObject::GetInstance() ;
+ while ( digit = (AliPHOSDigit * )nextdigit() ) {
+ for ( Int_t i = 0 ; i < digit->GetNprimary() ; i++ )
+ primary[i] = please->GimePrimaryParticle(digit->GetPrimary(i) ) ;
+ }
+ </pre>
+ <h4>
+ Reconstructed point to Digit
+ </h4>
+ A <a href="html/AliPHOSDigit.html">digit</a> has an additional data member which is the index of the object stored
+ in the <a href="http://root.cern.ch/root/html/TObjArray.html">TObjArray</a>. It is set by
+ <a href="html/AliPHOSv0.html">FinishEvent()</a>. A <a href="html/AliPHOSRecPoint.html">reconstructed point</a> containing
+ a list of digits, it can retrieve the digit object with the help of
+ <a href="html/AliPHOSIndexToObject.html">AliPHOSIndexToObject</a>:
+ <pre class="code">
+ // initialization
+ // open root file
+ TFile rootfile("junk.root") ;
+ // get AliRun object
+ gAlice = (AliRun *)rootfile.Get("gAlice") ;
+ // get detector object
+ AliPHOSv0 * phos = (AliPHOSv0 *)gAlice->GetDetector("PHOS") ;
+ // get the geometry associated with the detector
+ AliPHOSGeometry::GetInstance( phos->GetGeometry()->GetName(), phos->GetGeometry()->GetTitle() ) ;
+ // initializes the index to object converter
+ AliPHOSIndexToObject::GetInstance(phos) ;
+ // get the reconstructed points list
+ Int_t evt = 123 ;
+ TObjArray * recpointslist = phos->EmcRecPoints(evt) ;
+ // loop over reconstructed points
+ TIter nextrecpoint(recpointslist) ;
+ // get the pointer of the index to object converter
+ AliPHOSIndexToObject * please = AliPHOSIndexToObject::GetInstance() ;
+ AliPHOSEmcRecPoint * recpoint ;
+ while ( recpoint = (AliPHOSEmcRecPoint * )nextrecpoint() ) {
+ // get the associated digits list
+ Int_t * digitsindexeslist = recpoint->GetDigitsList() ;
+ // loop over the list of digits
+ for ( Int_t i = 0 ; i < recpoint->GetDigitsMultiplicity() ; i++ ) {
+ AliPHOSDigit * digit = please->GimeDigit(digitsindexeslist[i] ) ;
+ // get the primary particle associated with that digit
+ Int_t numberofprimaries = 0 ;
+ Int_t * prim = digit->GetPrimaries(numberofprimaries) ;
+ for (Int_t i = 0 ; i < numberofprimaries ; i++ )
+ // and print them
+ please->GimePrimaryParticle( prim[i] )->Print() ;
+ }
+ }
+ // or get the primaries directly from the reconstructed point
+ Int_t numberofprimaries = 0 ;
+ Int_t * prim = recpoint->GetPrimaries(numberofprimaries) ;
+ }
+ </pre>
+ <h4>
+ Track segment to reconstructed point
+ </h4>
+ A <a href="html/AliPHOSRecPoint.html">reconstructed point</a> has an additional data member which is the index of the object stored
+ in the <a href="http://root.cern.ch/root/html/TClonesArray.html">TClnesArray</a>. It is set by the
+ <a href="html/AliPHOSReconstructioner.html">reconstructioner</a>.
+ A <a href="html/AliPHOSTrackSegment.html">track segment</a> contains the index of one EMCA reconstructed points and two
+ PPSD reconstructed points, it can retrieve this reconstructed point objects with the help of
+ <a href="html/AliPHOSIndexToObject.html">AliPHOSIndexToObject</a>:
+ <pre class="code">
+ // initialization
+ // open root file
+ TFile rootfile("junk.root") ;
+ // get AliRun object
+ gAlice = (AliRun *)rootfile.Get("gAlice") ;
+ // get detector object
+ AliPHOSv0 * phos = (AliPHOSv0 *)gAlice->GetDetector("PHOS") ;
+ // get the geometry associated with the detector
+ AliPHOSGeometry::GetInstance( phos->GetGeometry()->GetName(), phos->GetGeometry()->GetTitle() ) ;
+ // initializes the index to object converter
+ AliPHOSIndexToObject::GetInstance(phos) ;
+ // get the track segments list
+ Int_t evt = 123 ;
+ TClonesArray * tracksegmentslist = phos->TrackSegments(evt) ;
+ // loop over track segments
+ TIter nexttracksegment(tracksegmentslist) ;
+ AliPHOSTrackSegment * tracksegment ;
+ // get the pointer of the index to object converter
+ AliPHOSIndexToObject * please = AliPHOSIndexToObject::GetInstance() ;
+ while ( tracksegment = (AliPHOSTrackSegment * )nexttracksegment() ) {
+ // get the associated reconstructed points
+ AliPHOSEmcRecPoint * emcrecpoint = please->GimeRecPoint(tracksegment->GetEmcRecPoint(), "emc" ) ;
+ AliPHOSPpsdRecPoint * ppsduprecpoint = please->GimeRecPoint(tracksegment->GetPpsdUpRecPoint(), "ppsd" ) ;
+ AliPHOSPpsdRecPoint * ppsdlowrecpoint = please->GimeRecPoint(tracksegment->GetPpsdLowRecPoint(),"ppsd" ) ;
+ // get the primaries particles
+ Int_t numberofprimariestoemc = 0 ;
+ Int_t * primemc = tracksegment->GetPrimariesEmc(numberofprimariestoemc) ;
+ Int_t numberofprimariestoppsdup = 0 ;
+ Int_t * primppsdup = tracksegment->GetPrimariesPpsdUp(numberofprimariestoppsdup) ;
+ Int_t numberofprimariestoppsdlow = 0 ;
+ Int_t * primppsdlow = tracksegment->GetPrimariesPpsdLow(numberofprimariestoppsdlow) ;
+ // print one as example
+ please->GimePrimaryParticle( primppsdlow[0] )->Print() ;
+ }
+ rootfile.Close() ;
+ gAlice = 0 ;
+ phos = 0 ;
+ recparticleslist = 0 ;
+ </pre>
+ <h4>
+ Reconstructed particle to Track segment
+ </h4>
+ A <a href="html/AliPHOSTrackSegment.html">track segment</a> has an additional data member which is the index of the object stored
+ in the <a href="http://root.cern.ch/root/html/TClonesArray.html">TClnesArray</a>. It is set by the
+ <a href="html/AliPHOSReconstructioner.html">reconstructioner</a>.
+ A <a href="html/AliPHOSRecParticle.html">reconstructed particle</a> contains the index of a track segment,
+ it can retrieve this reconstructed point objects with the help of
+ <a href="html/AliPHOSIndexToObject.html">AliPHOSIndexToObject</a>:
+ <pre class="code">
+ // initialization
+ // open root file
+ TFile rootfile("junk.root") ;
+ // get AliRun object
+ gAlice = (AliRun *)rootfile.Get("gAlice") ;
+ // get detector object
+ AliPHOSv0 * phos = (AliPHOSv0 *)gAlice->GetDetector("PHOS") ;
+ // get the geometry associated with the detector
+ AliPHOSGeometry::GetInstance( phos->GetGeometry()->GetName(), phos->GetGeometry()->GetTitle() ) ;
+ // initializes the index to object converter
+ AliPHOSIndexToObject::GetInstance(phos) ;
+ // get the reconstructed particles list
+ Int_t evt = 123 ;
+ TClonesArray * recparticleslist = phos->RecParticles(evt) ;
+ // loop over reconstructed particles
+ TIter nextrecparticle(recparticleslist) ;
+ AliPHOSRecParticle * recparticle ;
+ // get the pointer of the index to object converter
+ AliPHOSIndexToObject * please = AliPHOSIndexToObject::GetInstance() ;
+ while ( recparticle = (AliPHOSRecParticle * )nextrecparticle() ) {
+ // get the track segment ...
+ AliPHOSTrackSegment * tracksegment = recparticle->GetPHOSTrackSegment() ;
+ // and print it
+ tracksegment->Print() ;
+ // get the list of primaries ...
+ Int_t numberofprimaries = 0 ;
+ Int_t * prim = recparticle->GetPrimaries(numberofprimaries) ;
+ for (Int_t i = 0 ; i < numberofprimaries ; i++ )
+ // and print them
+ please->GimePrimaryParticle( prim[i] )->Print() ;
+ }
+ rootfile.Close() ;
+ gAlice = 0 ;
+ phos = 0 ;
+ recparticleslist = 0 ;
+ </pre>
+ A short cut allows to access the primaries at the origin of the reconstructed particle:
+ <pre class="code">
+ Int_t numberofprimaries = 0 ;
+ Int_t * prim = recparticle->GetPrimariesPpsdLow(numberofprimaries) ;
+ </pre>
<hr>
<address class="left">
-© <a href="mailto:
aphecetc@in2p3.fr">Groupe Photons Subatech</a> <a href="http://www-subatech.in2p3.fr/~photons/subatech/en_index.shtml">[Go
+© <a href="mailto:
schutz@in2p3.fr">Groupe Photons Subatech</a> <a href="http://www-subatech.in2p3.fr/~photons/subatech/en_index.shtml">[Go
to the GPS Home Page]</a></address>
<address class="right">
<!-- Created: Tue Oct 26 19:52:56 CEST 1999 -->
<!-- hhmts start -->
-Last modified: Wed Dec 1 18:54:10 CET 1999
+Last modified: Sun Mar 26 17:20:12 CEST 2000
<!-- hhmts end --></address>
-<div align=right><a href="http://validator.w3.org/check/referer"><img SRC="vh40.gif" ALT="Valid HTML 4.0!" BORDER=0 height=31 width=88></a><a href="http://jigsaw.w3.org/css-validator"><img SRC="vcss.gif" ALT="Valid CSS!" BORDER=0 height=31 width=88></a></div>
+<!-- <div align=right><a href="http://validator.w3.org/check/referer"><img SRC="images/vh40.gif" ALT="Valid HTML 4.0!" BORDER=0 height=31 width=88></a><a href="http://jigsaw.w3.org/css-validator"><img SRC="images/vcss.gif" ALT="Valid CSS!" BORDER=0 height=31 width=88></a></div> -->
</body>
</html>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"
"http://www.w3.org/TR/REC-html40/loose.dtd">
<html>
-<head>
- <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
- <meta name="GENERATOR" content="Mozilla/4.51 [en] (X11; I; Linux 2.2.5-15 i686) [Netscape]">
- <title>PHOS Reconstruction Proposal</title>
-<link REL="stylesheet" href="http://www-subatech.in2p3.fr/~photons/gps_alice.css" type="text/css">
-</head>
-<body>
-
-<h1 class="page-header">
-Simulation</h1>
-
-<h2>Event generation</h2>
-
-<P>
-One of the main ingredients to simulate the physic performance of PHOS is the
-generation of a realistic background in central Pb+Pb collisions at LHC energies. <BR> <BR>
-However, most of ALICE subdetectors are sensitive to charged particles and, in
-consequence, the charged hadronic background is the most important one (see for
-instance <A HREF="http://www.cern.ch/ALICE/Projects/offline/evgen/Welcome.html">AliGenHIJINGPara class</A>). <BR>
-However, PHOS detector is sensitive to most of particles: electrons, muon, photons, charged and neutral hadrons. In
-particular the main background is generated by the electromagnetic decay of the neutral pion, which was omitted
-in the background generators classes defined in aliroot package 3.01. <BR>
-<BR>
-Within this respect, we have defined a new class:
-<A HREF="ttp://www.cern.ch/ALICE/Projects/offline/aliroot/roothtml/src/AliGenPHOSlib.cxx.html">AliGenPHOSlib class</A>,
-and adapted the
-<A HREF="http://www.cern.ch/ALICE/Projects/offline/aliroot/roothtml/src/AliGenParam.cxx.html">AliGenParam class</A> class in
-order to be able to simulate the full neutral and charged background which is present in heavy-ion collisions.
-All these stuff has been included in the aliroot version 3.02.<BR>
-<BR>
-
-Enclosed, an exemple of the aliroot config file is reported.
-This neutral and charged background contains pi+, pi-,pi0,K+,K-,kshort,Klong,eta,omega,p. p bar, n and n bar with
-relative yields given by hijing in Pb+Pb central collisions (results from venus or shaker are close to the hijing ones).
-Pion transverse momentum (Pt) distribution is taken from AliGenMUONlib class, version 3.01 of aliroot:
-Pt Parameterization CDF (PRL 61(88) 1819): Power law for Pt > 500 MeV and Mt scaling below (slope T=160 MeV).
-Meson Pt distributions are calculated by mt-scaling with pions (see
-<A HREF="http://www.cern.ch/ALICE/Projects/offline/evgen/Welcome.html">AliGenMUONlib or AliGenPHOSlib class</A>).
-
-<PRE class="code">
-//=======================================================================
-// ************* STEERING parameters FOR ALICE SIMULATION **************
-// --- Specify event type to be tracked through the ALICE setup
-// --- All positions are in cm, angles in degrees, and P and E in GeV
-//
-// The following Cocktail generator is defined to simulate the neutral and
-// charged background in the ALICE detector. This background is important
-// in the case of photon detector as PHOS. We simulated a cocktail of
-// pions (pi+, pi- and pi0) , kaons (K+, K-, Kshort and Klong), eta mesons,
-// omega mesons and main baryons (protons, antiprotons, neutrons and
-// antineutrons)
-//
-// 1-Nov-1999 Gines MARTINEZ, GPS @ SUBATECH, Nantes, France
-//
-Int_t ParticleDensity = 8000 // Number of particles created in the selected rapidity range
-Int_t NumberOfPions = 0.77 * ParticleDensity ; // ~77% of pions: pi^+, pi^- and pi^0 with equal probability
-Int_t NumberOfKaons = 0.11 * ParticleDensity ; // ~11% of kaons: K^+, K^-, K_short and K_long with equal probability
-Int_t NumberOfEtas = 0.04 * ParticleDensity ; // ~4.0% of eta mesons
-Int_t NumberOfOmegas = 0.01 * ParticleDensity ; // ~1.0% of omega mesons
-Int_t NumberOfBaryons = 0.07 * ParticleDensity ; // ~7.0% of baryons: p, pbar, n and nbar with equal probability
-
-AliGenCocktail *gener = new AliGenCocktail(); \\ Cocktail class
- gener->SetPtRange(.5,5.); // Transverse momentum range
- gener->SetPhiRange(0.,360.); // Azimuthal angle range
- gener->SetYRange(-0.5,0.5); // Pseudorapidity range
- gener->SetOrigin(0,0,0); // Vertex position
- gener->SetSigma(0,0,5.6); // Sigma in (X,Y,Z) (cm) on IP position
-//
-// P I O N S
- AliGenParam *generpion = new AliGenParam(NumberOfPions,Pion,
- AliGenPHOSlib::GetPt(Pion), AliGenPHOSlib::GetY(Pion), AliGenPHOSlib::GetIp(Pion) );
- generpion->SetWeighting(non_analog); // Selecting the Pt distribution provided by AliGenPHOSlib::GetPt
- generpion->SetForceDecay(nodecay); // Requiring that the generated particle is directly tracked by GEANT
-//
-// K A O N S
- AliGenParam *generkaon = new AliGenParam(NumberOfKaons,Kaon,
- AliGenPHOSlib::GetPt(Kaon), AliGenPHOSlib::GetY(Kaon), AliGenPHOSlib::GetIp(Kaon) );
- generkaon->SetWeighting(non_analog); // Selecting the Pt distribution provided by AliGenPHOSlib::GetPt
- generkaon->SetForceDecay(nodecay); // Requiring that the generated particle is directly tracked by GEANT
-//
-// E T A S
- AliGenParam *genereta = new AliGenParam(NumberOfEtas,Eta,
- AliGenPHOSlib::GetPt(Eta), AliGenPHOSlib::GetY(Eta), AliGenPHOSlib::GetIp(Eta) );
- genereta->SetWeighting(non_analog); // Selecting the Pt distribution provided by AliGenPHOSlib::GetPt
- genereta->SetForceDecay(nodecay); // Requiring that the generated particle is directly tracked by GEANT
-//
-// O M E G A S
- AliGenParam *generomega = new AliGenParam(NumberOfOmegas,Omega,
- AliGenPHOSlib::GetPt(Omega), AliGenPHOSlib::GetY(Omega), AliGenPHOSlib::GetIp(Omega) );
- generomega->SetWeighting(non_analog); // Selecting the Pt distribution provided by AliGenPHOSlib::GetPt
- generomega->SetForceDecay(nodecay); // Requiring that the generated particle is directly tracked by GEANT
-//
-// B A R Y O N S
-
- AliGenParam *generbaryon = new AliGenParam(NumberOfBaryons,Baryon,
- AliGenPHOSlib::GetPt(Baryon), AliGenPHOSlib::GetY(Baryon), AliGenPHOSlib::GetIp(Baryon) );
- generbaryon->SetWeighting(non_analog); // Selecting the Pt distribution provided by AliGenPHOSlib::GetPt
- generbaryon->SetForceDecay(nodecay); // Requiring that the generated particle is directly tracked by GEANT
+ <head>
+ <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
+ <meta name="GENERATOR" content="Mozilla/4.51 [en] (X11; I; Linux 2.2.5-15 i686) [Netscape]">
+ <title>PHOS Geometry in AliRoot</title>
+ <link REL="stylesheet" href="http://www-subatech.in2p3.fr/~photons/gps_alice.css" type="text/css">
+ <body>
-
- gener->AddGenerator(generpion,"pion",1.);
- gener->AddGenerator(generkaon,"kaon",1.);
- gener->AddGenerator(genereta,"eta",1.);
- gener->AddGenerator(generomega,"omega",1.);
- gener->AddGenerator(generbaryon,"baryon",1.);
- gener->Init();
-</pre>
-
-
-The resulting hit and digit TTree's (one per event) will be stored
-in the root file on disk.
-
-<hr>
-<address class="left">
-© <a href="mailto:aphecetc@in2p3.fr">Groupe Photons Subatech</a> <a href="http://www-subatech.in2p3.fr/~photons/subatech/en_index.shtml">[Go
-to the GPS Home Page]</a></address>
+ <h1 class="page-header">
+ Geometry & Materials
+ </h1>
+ <h1>
+ Simulation
+ </h1>
+ The simulation is done in two steps, one which describes the detector geometry
+ and material and one which does the particle tracking and stores the hits
+ and digits in a <a href="http://root.cern.ch/root/html/TTree.html">TTree</a> itself written on a disk file. These two steps are
+ steered through the Config.C file(<a href="PHOSConfig_Central.C">example</a>),
+ a root macro launched at the AliRoot prompt. To customize this file you must:
+ <br><br>
+ <ol>
+ <li>
+ select a file name for the root output:
+ <pre class="code">
+ //=======================================================================
+ // Create the output file
+ sprintf(filename,"<b>myfilename</b>.root");
+ </pre>
+ </li>
+ <li>
+ Define your event generator and simulations parameters:
+ <pre class="code">
+ AliGenCocktail *gener = new AliGenCocktail(); // Cocktail class
+ gener->SetPtRange(.02,10.00); // Transverse momentum range
+ gener->SetPhiRange(180.,360.); // Azimuthal angle range
+ gener->SetYRange(-0.25,0.25); // Pseudorapidity range
+ gener->SetOrigin(0,0,0); // Vertex position
+ gener->SetSigma(0,0,5.6); // Sigma in (X,Y,Z) (cm) on IP position
+ gener->Init(); // Initialize the generator
+ </pre>
+ </li>
+ <li>
+ Select the detector seen by the tracking:
+ <pre class="code">
+ Int_t iPHOS=1; // PHOS is in
+ Int_t iPMD=0; // PMD is out
+ </pre>
+ </li>
+ <li>
+ Create a PHOS object (<b>GPS2</b> is so far the unique configuration option, see below):
+ <pre class="code">
+ if(iPHOS) {
+ //=================== PHOS parameters ===========================
+ AliPHOS *PHOS = new AliPHOSv0("PHOS","<b>GPS2</b>");
+ </pre>
+ </li>
+ </ol>
+ <p>
+ You van now run the simulation by entering the following command at the aliroot prompt:
+ <pre class="code">
+ aliroot> gAlice->Run(1,"PHOSConfig_Central.C");
+ </pre>
+ <h1>
+ Geometry
+ </h1>
+ <h4>
+ Definition
+ </h4>
+ PHOS consists of two distinct parts. The calorimeter, named EMCA, consists
+ of the PbW04 crystals within their housing. The crystals are assembled
+ in <i>fNModules</i> modules of <i>fNPhi </i>rows along the x-axis direction
+ and <i>fNZ</i> modules along the z-axis direction. Since the total number
+ of crystals and their layout within ALICE is presently (11/11/1999) not
+ final it was decided to fully parametrize the geometry. A change in any
+ of the three previously defined parameters will provide automatically a
+ new layout of the modules.
+ <br>The second part of PHOS is the charged particle identifier. Since until
+ end of 2000 no decision will be taken on the final design of this element
+ two or more versions can be considered. Today (11/11/1999) only one version
+ is implemented and is named PPSD for PHOS Pre-Shower Detector. It consists
+ of a first layer of <i>fNumberOfModulesPhi</i> x <i>fNumberOfModulesZ </i>gas
+ detectors per PHOS module, each detectors being subdivided into <i>fNumberOfPadsPhi</i>
+ x <i>fNumberOfPadsZ </i>gas cells, a Lead converter and a second layer
+ of gas detectors identical to the first layer. This second part is positionned
+ on top of the EMCA module.
+ <p>
+ The class <a href="./html/AliPHOSv0.html"> AliPHOSv0 </a> ( <a href="./html/AliPHOSv0_Tree.ps"> inheritance tree </a>)
+ describes this geometry. We have defined also a class
+ <a href="./html/AliPHOSv1.html"> AliPHOSv1 </a> ( <a href="./html/AliPHOSv1_Tree.ps"> inheritance tree </a>)
+ which in addition contains the photodiode response and the light transport through the crystal.
+ <p>
+ The parameters of the geometry are given in class <a href="./html/AliPHOSGeometry.html"> AliPHOSGeometry </a>( <a href="./html/AliPHOSGeometry_Tree.ps"> inheritance tree </a>)
+ <br><br>
+ <center>
+ <img SRC=" images/EMCinAlice.gif" ALT="Geant Tree for PHOS" >
+ <br><br>
+ <b> Figure 1.a: </b> <i> GEANT Tree which describes the EMC-PHOS geometry </i>
+ </center>
+ <P>
+ <center>
+ <img SRC=" images/PPSDinAlice.gif" ALT="Geant Tree for PHOS" >
+ <br><br>
+ <b> Figure 1.b: </b> <i> GEANT Tree which describes the PPSD-PHOS geometry </i>
+ </center>
+ <h4>
+ Implementation
+ </h4>
+ <p>
+ <center>
+ <img SRC="./images/aliphossimulation.gif" ALT="Geom/Simul class diagram" >
+ <br><br>
+ <b> Figure 2.: </b> <i> Class diagram for the geometry/simulation package </i>
+ </center>
+ <p>
+ <a href="./html/AliPHOS.html"><i><u>AliPHOS</u></i></a>: This is the base class. It derives from <i>AliDetector.
+ </i>It's only purpose is to describe the materials
+ (à la <i>AliMC</i>) needed for the EMCA and PPSD construction.
+ <p>
+ <a href="./html/AliPHOSv0.html"><i><u>AliPHOSv4</u></i></a>: It derives from <i>AliPHOS</i>.
+ <br>
+ <ul>
+ <li>
+ It sets up the geometry for the Root display (<i>AliPHOSv4::BuildGeometry()</i>)
+ and for the GEANT tracking (<i>AliPHOSv4::CreateGeometry()</i>).
+ </li>
+ <li>
+ It watches the tracks passing through the active media of EMCA and PPSD
+ (<i>AliPHOSv4::StepManager()</i>).
+ </li>
+ <li>
+ It stores the hits (<i>AliPHOSv4::AddHit()</i>), using the <i>AliPHOSHit</i>
+ class.
+ </li>
+ <li>
+ It stores the digits (<i>AliPHOSv4::FinishEvent()</i>), using the <i>AliPHOSDigit</i>
+ class.
+ </li>
+ </ul>
+ <p>
+ <a href="./html/AliPHOSv1.html"><i><u>AliPHOSv1</u></i></a> : derives from <i>AliPHOSv0</i> and includes the light transport
+ in the crystal and the response of the PIN photodiode à la O. H. Oddland.
+ <p>
+ <a href="./html/AliPHOSvFast.html"><i><u>AliPHOSvFast</u></i></a> : used for <a href="fastsimulation.html">fast simulation</a>.
+ <p>
+ <a href="./html/AliPHOSGeometry.html"><i><u>AliPHOSGeometry</u></i></a> : It derives from <i>TObject</i> to make it
+ persistent. It is a singleton, i.e., a pointer to the unique instance of
+ this class is obtained by:
+ <center>
+ <pre class="code">
+ AliPHOSGeometry * Geom = AliPHOSGeometry::GetInstance()
+ </pre>
+ </center>
+ <ul>
+ <li>
+ It sets the various parameters for the geometry description and provides
+ the method to access all the parameters. To avoid cumbersome macros at
+ run time these parameters can only be changed manually in the source code.
+ </li>
+ <li>
+ It provides the method to convert the absolute detector Id (crystal in
+ EMCA or pad in PPSD) into a relative Id : PHOS module number, PPSD module
+ number, row, column (<i>AliPHOSGeometry::AbsToRelNumbering()</i>) and the
+ reverse operation (<i>AliPHOSGeometry::RelToAbsNumbering()</i>).
+ </li>
+ <li>
+ It provides the method to convert an absolute Id into a three-vector giving
+ the position of the detector in ALICE (<i>AliPHOSGeometry::RelPosInAlice()</i>).
+ </li>
+ </ul>
+ <p>
+ <a href="./html/AliPHOSHit.html"><i><u>AliPHOSHit</u></i></a>: It derives from <i>AliHit</i>. It stores the
+ hits as the pair (absolute Id, deposited energy). The hits presently are stored in the hit TTree
+ as one hit per elementary cell (EMC crystal or PPSD gas cell) (See the
+ the AddHit() method in <i>AliPHOSv0</i>).
+ <p>
+ <a href="./html/AliPHOSDigit.html"><i><u>AliPHOSDigit</u></i></a> : It derives from <i>AliDigit</i>. It stores
+ the digits as the pair (absolute Id, energy) in the digit TTree (see
+ the FinishEvent() method in <i>AliPHOSv0</i>).
+ <h1>
+ Usage
+ </h1>
+ <p>
+ <pre class="code">
+ Int_t iPHOS=1;
+ if(iPHOS) {
+ AliPHOS * phos = new AliPHOSv4("PHOS", char * name) ;
+ </pre>
+ <br>
+ where name can take the following values:
+ <ul>
+ <li>
+ <i>GPS2</i>: will create EMCA plus PPSD
+ <br><br>
+ <center>
+ <img SRC="images/AliPHOSv0AllViews.gif" ALT="ROOT display of PHOS: All Views" >
+ <b> Figure 3a.: </b> <i> ROOT Display of ALICE: All Views </i>
+ <p>
+ <img SRC="images/AliPHOSv0FrontView.gif" ALT="ROOT display of PHOS: Front View" >
+ <b> Figure 3b.: </b> <i> ROOT Display of ALICE: Front Views </i>
+ <p>
+ <img SRC="images/AliPHOSv03DView1.gif" ALT="ROOT display of PHOS: 3D View" >
+ <b> Figure 3c.: </b> <i> ROOT Display of ALICE: All View3 </i>
+ <p>
+ <img SRC="images/AliPHOSv0PPSDFrontView.gif" ALT="Zoom on PPSD: Front View " >
+ <b> Figure 4.a: </b> <i> ROOT Display of ALICE: zoom on PPSD, Front Views </i>
+ <p>
+ <img SRC="images/AliPHOSv0PPSDPerspectiveView.gif" ALT="Zoom on PPSD: Perspective View " >
+ <b> Figure 4.b: </b> <i> ROOT Display of ALICE: zoom on PPSD, Perspective View </i>
+ </center> <br><br>
+ </li>
+ <li>
+ more to come from Protvino (EMCA plus other CPV type)</li>
+ </ul>
+ <br>
+ EMCA consists of 5 modules of 64x64 modules each, positionned at
+ azimuthal angles -40, -20, 0, +20, +40 (see figures). PPSD consists per
+ EMCA module of 2 layers of 4x4 gas detectors each, each detector having
+ 24x24 gas cells.
+ <h1>
+ Result
+ </h1>
-<address class="right">
-<!-- Created: Tue Oct 26 19:52:56 CEST 1999 -->
-<!-- hhmts start -->
-Last modified: Mon Nov 15 18:55:06 CET 1999
-<!-- hhmts end --></address>
+ <hr>
+ <address class="left">
+ © <a href="mailto:schutz@in2p3.fr">>Groupe Photons Subatech (Yves SCHUTZ)</a>
+ <a href="http://www-subatech.in2p3.fr/~photons/subatech/en_index.shtml">[Go
+ to the GPS Home Page]</a>
+</address>
+ <!-- Created: Wed Nov 17 12:16:58 CET 1999 -->
+ <!-- hhmts start -->
+Last modified: Sun Mar 26 17:37:28 CEST 2000
+<!-- hhmts end -->
+ <!-- <div align=right><a href="http://validator.w3.org/check/referer"><img SRC="images/vh40.gif" ALT="Valid HTML 4.0!" BORDER=0 height=31 width=88></a><a href="http://jigsaw.w3.org/css-validator"><img SRC="images/vcss.gif" ALT="Valid CSS!" BORDER=0 height=31 width=88></a></div>-->
-<div align=right><a href="http://validator.w3.org/check/referer"><img SRC="vh40.gif" ALT="Valid HTML 4.0!" BORDER=0 height=31 width=88></a><a href="http://jigsaw.w3.org/css-validator"><img SRC="vcss.gif" ALT="Valid CSS!" BORDER=0 height=31 width=88></a></div>
-
-</body>
+
+ </body>
</html>
+
git://git.uio.no / u / mrichter / AliRoot.git / commitdiff