Central Pre-Radiator Clustering

2.1 - Track based Clustering
In the case of track based clustering each track is extrapolated to the CPR and the surrounding wires upto N_MAX which can be specified are included around this track. The cluster charge is defined as the sum of Q_i for i=1,N_MAX wires included in the cluster, and the position is the energy weighted sum of the individual wire positions. (What we call wire actually means a cell. So we have 16 cells in each chamber)

2.1 - Seed based Clustering
In the case of Unbiased or Energy Based , all wires above a seed threshold (changeable in the talk-to) in decreasing order of energy, form the seed for the wire collection and i=1,N_MAX wires (above a certain wire threshold ) are included around each seed and the seed wire together with its surrounding wires are marked used, to be excluded from the list of wires to be used in the next cluster. In this way the clustering continues until there are no wires left above the specified thresholds.

Default parameters used in the clustering (CprDefs.hh)
Charge/ADC (fC/count)	1.67
CPR pedestal	50 ADC counts
Seed Threshold	50 fC
Wire Threshold	30 fC
No. wires included around seed	3
Min. wires in cluster	1
Max wires in cluster	3

3 - CPR Objects
CprCluster is a Streamable Object deriving from ShowerMaxCluster.
The usable base class accessor functions are :

int	module	Wedge no. of the cluster
int	side	Side (0=west, 1=east)

The other usable accessor functions are :

double	x_wire	Local X position of the cluster
double	energy_wire	Energy of the cluster
int	trackId	Track # matched to cluster (0 for unbiased)
CdfTrack_clnk	Track	Link to Track matched to cluster (NULL for unbiased)
const vector < CprWire>	wires	vector of wires which make this cluster

The accessors for CprWire are :

double	getPulseHeight	CPR wire charge (in fC)
int	getWireNo	Wire No. (0-31)
int	getModuleNo	Wedge No.
double	getSide	Side (E/W)

CprClusterColl is a storable object and is accessible from the event. The 2 kinds of collection are:
"TrackBased_CprClusterCollection"
"SeedBased_CprClusterCollection"

See examples to access CPR Clusters.


4 - Examples
Parameters changeable in the tcl :

Name	Description	Default
CprPtmin	Min PT of tracks considered	0.5
CprEtamin	Min Eta of Tracks	-1.2
CprEtamax	Max Eta of Tracks	1.2
CprNumberWires	Number of wires including seed wire in the collection	3
maxwiresclus	Max. number of wires in cluster	3
minwiresclus	Min. number of wires for cluster	1
wirecollstrat	SeedBased(1) or TrackBased(0) or both(3)	3
CprSeedThrs	Threshold cut for Seed Wire	50.0
CprWireThrs	Threshold cut for Wires included	30.0
CprClusSeedThrs	Threshold cut for Seed wire in cluster	50.0
CprClusWireThrs	Threshold cut for wires in cluster	30.0
CprClusEnergyThrs	Cut for total Cluster Energy	50.0

4.2 - To extrapolate a track to the CPR
The CprWireCollectionMaker implements functions to extrapolate the track and to find the wire hit from the extrapolated information. The examples below are extracted from CprClusterModule (CPR Clustering Module).
// extrapolate a track :
CprWireCollectionMaker wireCol;
// Loop over tracks
for (CdfTrackView::const_iterator i = theTracks->contents().begin(); i != theTracks->contents().end(); ++i) {
const CdfTrack_lnk & theTrack = *i;
wireCol.extrapolate_track(theTrack);

// Access extrapolated information :
float Xloc = wireCol.get_Xlocal(); // Local x and z position
float Zloc = wireCol.get_Zlocal();
float phi_glob = wireCol.Phi_global(); // Global phi and eta
float eta_glob = wireCol.Eta_global();
float side = wireCol.Side(); // Side (W/E)
float wedge = wireCol.Wedge(); // Wedge No.
}

4.3 - Accessing CPR Clusters
Say, you want to look at all track-based CPR clusters in an event:

std::string description = "TrackBased_CprClusterCollection"; // Track Based
//std::string description = "SeedBased_CprClusterCollection"; // Seed Based (Unbiased)
CprClusterColl_ch cprClusterColl;
StorableObject::SelectByDescription selector( description );
EventRecord::ConstIterator iter( anEvent, selector );
cprClusterColl = CprClusterColl_ch(iter);

// loop over the clusters
for (CprClusterColl::const_iterator cprIter = cprClusterColl->contents().begin();
cprIter != cprClusterColl->contents().end(); ++cprIter) {
CprCluster cprclus = *cprIter;
// Get the position
double x_clus = cprclus.x_wire();
}

5 - Validation
Validation for the CPR and CES is performed by CprCesValidationModule. It is run in Production.
The output production root files can be found on fcdflnx3.fnal.gov in /cdf/opr/cdfprod0 for different versions
. For some more useful validation results see Rob Snihur's page

Single electron simulated events :
Cluster charge distribution for Fake electrons
DX (cm) between Extrapolated track position and cluster position.
CPR Mip Response

Data commissioning Run 2000:
CPR Pedestal distribution
Track-cluster match