diff -N ReconstructedParticleChecker.java
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ ReconstructedParticleChecker.java	11 Apr 2013 02:38:20 -0000	1.1
@@ -0,0 +1,123 @@

+package org.lcsim.hps.users.omoreno;
+
+//--- java ---//
+import java.util.ArrayList;
+import java.util.List;
+
+//--- hep ---//
+import hep.aida.IHistogram1D;
+import hep.aida.IPlotter;
+import hep.physics.vec.BasicHep3Vector;
+import hep.physics.vec.Hep3Vector;
+import hep.physics.vec.VecOp;
+
+//--- lcsim ---//
+import org.lcsim.event.EventHeader;
+import org.lcsim.event.ReconstructedParticle;
+import org.lcsim.event.Track;
+import org.lcsim.event.Cluster;
+import org.lcsim.util.Driver;
+import org.lcsim.util.aida.AIDA;
+import org.lcsim.geometry.Detector;
+
+//--- hps-java ---//
+import org.lcsim.hps.recon.tracking.SvtTrackExtrapolator;
+
+/**
+ * 
+ * @author Omar Moreno <[log in to unmask]>
+ * @version $Id: ReconstructedParticleChecker.java,v 1.1 2013/04/11 02:38:20 omoreno Exp $
+ *
+ */
+public class ReconstructedParticleChecker extends Driver {
+	
+	SvtTrackExtrapolator extrapolator = new SvtTrackExtrapolator(); 
+	private AIDA aida; 
+	private List<IPlotter> plotters = new ArrayList<IPlotter>(); 
+
+	IHistogram1D xPositionResidual;
+	IHistogram1D yPositionResidual;
+	IHistogram1D zPositionResidual;
+	IHistogram1D r;
+	
+	// Collection Names
+	private String finalStateParticlesCollectionName = "FinalStateParticles";
+	
+	boolean debug = true; 
+	int plotterIndex = 0; 
+	
+	public ReconstructedParticleChecker(){} 
+	
+	protected void detectorChanged(Detector detector){
+		super.detectorChanged(detector);
+		
+		// Setup AIDA
+		aida = AIDA.defaultInstance(); 
+		aida.tree().cd("/");
+		
+		plotters.add(PlotUtils.setupPlotter("Track-Cluster Position Residual", 2, 2));
+		xPositionResidual = aida.histogram1D("x Residual", 100, -100, 100);
+		yPositionResidual = aida.histogram1D("y Residual", 100, -100, 100);
+		zPositionResidual = aida.histogram1D("z Residual", 100, -100, 100);
+		r = aida.histogram1D("r", 100, -100, 100);
+		PlotUtils.setup1DRegion(plotters.get(plotterIndex), "x Residual", 0, "delta x [mm]", xPositionResidual);
+		PlotUtils.setup1DRegion(plotters.get(plotterIndex), "y Residual", 1, "delta y [mm]", yPositionResidual);
+		PlotUtils.setup1DRegion(plotters.get(plotterIndex), "z Residual", 2, "delta z [mm]", zPositionResidual);
+		PlotUtils.setup1DRegion(plotters.get(plotterIndex), "r", 3, "r [mm]", r);
+		
+		
+		for(IPlotter plotter : plotters){
+			plotter.show(); 
+		}
+	}
+	
+	public void process(EventHeader event){
+		
+		// If the event doesn't contain any final state reconstructed 
+		// particles, skip the event 
+		if(!event.hasCollection(ReconstructedParticle.class, finalStateParticlesCollectionName)){
+			this.printDebug("Event does not contain ReconstructedParticles");
+			return;
+		}
+		
+		// Get the collections of reconstructed final state particles from the
+		// event
+		List<ReconstructedParticle> finalStateParticles 
+			= event.get(ReconstructedParticle.class, finalStateParticlesCollectionName); 
+				
+	
+		// Loop over all of the reconstructed particles in the event
+		for(ReconstructedParticle finalStateParticle : finalStateParticles){
+			
+			// Get the list of clusters from the event
+			List<Cluster> ecalClusters = finalStateParticle.getClusters(); 
+				this.printDebug("Number of Ecal clusters: " + ecalClusters.size()); 
+			if(ecalClusters.isEmpty()){
+				this.printDebug("Number of Ecal clusters: " + ecalClusters.size()); 
+				this.printDebug("List of Ecal cluster is empty ... skipping");
+				continue; 
+			}
+			
+			// Get the list of tracks from the event
+			List<Track> tracks = finalStateParticle.getTracks(); 
+			if(tracks.isEmpty()){
+				this.printDebug("List of tracks is empty ... skipping");
+				continue; 
+			}
+			extrapolator.setTrack(tracks.get(0));
+		
+			Hep3Vector ecalPosition = new BasicHep3Vector(ecalClusters.get(0).getPosition()); 
+			Hep3Vector trackPositionAtEcal = extrapolator.extrapolateTrack(ecalPosition.z()); 
+			xPositionResidual.fill(trackPositionAtEcal.x() - ecalPosition.x());
+			yPositionResidual.fill(trackPositionAtEcal.y() - ecalPosition.y());
+			zPositionResidual.fill(trackPositionAtEcal.z() - ecalPosition.z());
+			r.fill(VecOp.sub(trackPositionAtEcal, ecalPosition).magnitude());
+		}
+		
+	}
+	
+	private void printDebug(String debugMessage){
+		if(debug)
+			System.out.println(this.getClass().getSimpleName() + ": " + debugMessage); 
+	}
+}