lcsim/src/org/lcsim/util/decision

diff -N UnphysicalTrackDecision.java
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ UnphysicalTrackDecision.java	22 Oct 2008 21:08:28 -0000	1.1
@@ -0,0 +1,78 @@

+package org.lcsim.util.decision;
+
+import java.util.*;
+import hep.physics.vec.*;
+import org.lcsim.event.*;
+import org.lcsim.util.*;
+
+public class UnphysicalTrackDecision extends Driver implements DecisionMakerSingle<Track> {
+
+    /** Simple constructor. */
+    public UnphysicalTrackDecision() {
+	// Empty
+    }
+
+    protected double m_eventEnergy = Double.NaN;
+
+    /** Check if track has unphysical energy (greater than sqrt(s)/2). */
+    public boolean valid(Track tr) {
+	double mom = (new BasicHep3Vector(tr.getMomentum())).magnitude();
+	if (Double.isNaN(m_eventEnergy)) {
+	    // We don't know the event energy so we can't test tracks.
+	    // Assume they're all OK.
+	    return true;
+	} else if (mom < m_eventEnergy * 0.52) {
+	    // Track has half of event energy or less -- OK.
+	    // (Using 0.52 instead of 0.5 to allow a little tolerance for measurement
+	    // uncertainties, numerical precision, etc.)
+	    return true;
+	} else {
+	    // Unphysical energy
+	    return false;
+	}
+    }
+
+    /** Process: Used to cache event energy. */
+    public void process(EventHeader event) {
+	List<MCParticle> truthList = event.getMCParticles();
+	// Scan for the initial e+ e- pair, which have no parents:
+	MCParticle initialElectron = null;
+	MCParticle initialPositron = null;
+	for (MCParticle part : truthList) {
+	    if (part.getParents().size()==0) {
+		int pdg = part.getPDGID();
+		if (pdg == 11) {
+		    // Electron candidate
+		    if (initialElectron == null) {
+			// No previously found electron -- this is likely the one.
+			initialElectron = part;
+		    } else {
+			// Already found a parentless electron. Check which has higher energy:
+			if (part.getEnergy() > initialElectron.getEnergy()) {
+			    initialElectron = part;
+			}
+		    }
+		} else if (pdg == -11) {
+		    // Positron candidate
+		    if (initialPositron == null) {
+			// No previously found positron -- this is likely the one.
+			initialPositron = part;
+		    } else {
+			// Already found a parentless posittron. Check which has higher energy:
+			if (part.getEnergy() > initialPositron.getEnergy()) {
+			    initialPositron = part;
+			}
+		    }
+		}
+	    }
+	}
+
+	if (initialElectron==null || initialPositron==null) {
+	    // Something went wrong -- set event energy to NaN so that we don't exclude any tracks.
+	    m_eventEnergy = Double.NaN;
+	} else {
+	    // OK -- found both. Event energy is simply their sum.
+	    m_eventEnergy = initialElectron.getEnergy() + initialPositron.getEnergy();
+	}
+    }
+}