ElastWagon: replaced counter-based prescale with random number extraction because…

src/main/java/org/jlab/jnp/grapes/custom-services/ElastWagon.java

@@ -5,75 +5,56 @@
 import org.jlab.jnp.hipo4.data.Event;
 import org.jlab.jnp.hipo4.data.SchemaFactory;
 import java.util.ArrayList;
+import java.util.Random;
 
 /**
  * 
  * Skim for elastic e- events
- * e- events are prescaled by THRESHOLD for elastic angle theta_ec<theta_pc
+ * e- events are prescaled by PRESCALE for elastic angle theta_ec<theta_pc
  * corresponding to theta_p cutoff angle THETA_PC 
  *
  * @author lcsmith
  */
 public class ElastWagon extends BeamTargetWagon {
 
-    private static         int callCount = 0;
-    private static final   int THRESHOLD = 10;
-    private static final double THETA_PC = 40;
+    private static final   int PRESCALE = 10;
+    private static final double THETA_PC = Math.toRadians(40);
+    private static       double THETA_EC = 0;
     private static final double    W_CUT = 1.2;
 
+    private Random random = new Random();
+
     public ElastWagon(){
         super("ElastWagon","lcsmith","0.3");
     }
 
     @Override
     public boolean init(String jsonString) {
-        return super.init(jsonString);
-    }
-
-    private double getMM(LorentzVector Vb, LorentzVector Vt, LorentzVector Ve, LorentzVector...Vx) {
-        LorentzVector VmissN = new LorentzVector(0,0,0,0);
-        VmissN.add(Vb);
-        VmissN.add(Vt);
-        VmissN.sub(Ve);
-        for (Object LV : Vx) VmissN.sub((LorentzVector) LV);
-        return VmissN.mass2();
+        boolean status = super.init(jsonString);
+        THETA_EC = 2*Math.atan(1/(Math.tan(THETA_PC)*(1+beamEnergy/targetMass))); //electron pre-scale theta        
+	return status;
     }
 
     @Override
     public boolean processDataEvent(Event event, SchemaFactory factory) {
 
         Bank RecPart = new Bank(factory.getSchema("REC::Particle"));
-        Bank Config  = new Bank(factory.getSchema("RUN::config"));
-
-        event.read(RecPart);        
+        event.read(RecPart);
         if (RecPart==null || RecPart.getRows()==0) return false;
-        event.read(Config);        
-        if (Config==null ||  Config.getRows()==0)  return false;
 
-        final int THRESHOLD = 10; //pre-scale threshold
-
-        int runno = Config.getInt("run",0);
-        if(runno==0) return false;
-
-        double eb = beamEnergy;        
         //       if (runno>=19204 && runno<19662) eb = 6.39463; //rgk-f23, rgk-s24
         //       if (runno>=19662 && runno<19894) eb = 8.47757; //rgk-s24
 
-        double mp = 0.93828; 
-        double theta_pc = Math.toRadians(THETA_PC); //proton theta cutoff       
-        double theta_ec = 2*Math.atan(1/(Math.tan(theta_pc)*(1+eb/mp))); //electron pre-scale theta        
-
         ArrayList<Integer> eleCandi = new ArrayList<>();
 
         for (int ipart=0; ipart<RecPart.getRows(); ipart++) {
 
             final int    pid = RecPart.getInt("pid",ipart);
-            final int charge = RecPart.getInt("charge",ipart);
             final int status = RecPart.getInt("status",ipart);       
 
             final boolean isFD = (int)(Math.abs(status)/1000) == 2;
 
-            if (pid==11 && isFD && charge < 0) eleCandi.add(ipart);
+            if (pid==11 && isFD ) eleCandi.add(ipart);
         }
 
         if (eleCandi.isEmpty() || eleCandi.size()>1) return false;
@@ -83,21 +64,17 @@ public boolean processDataEvent(Event event, SchemaFactory factory) {
         double epz  = RecPart.getFloat("pz",eleCandi.get(0));
         double  ee  = Math.sqrt(epx*epx+epy*epy+epz*epz);
 
-        LorentzVector VVB = new LorentzVector(0,0,eb,eb);
-        LorentzVector VVT = new LorentzVector(0,0,0,mp);
         LorentzVector VVE = new LorentzVector(epx,epy,epz,ee);
 
-        double WW  = Math.sqrt(getMM(VVB,VVT,VVE));
+        double WW  = this.getMissingVector(VVE).mass();
 
         if (WW > W_CUT) return false;    // W cut must go before theta_c cut!
 
-        if (VVE.theta() < theta_ec) {  //theta_ec cut
-            callCount++;            
-            if (callCount <  THRESHOLD) return false;
-            if (callCount == THRESHOLD) callCount=0;
+        if (VVE.theta() < THETA_EC) {  //theta_ec cut
+  	     return random.nextInt(PRESCALE)<1;
         }
 
-        return true;          
+        return true;
     }
 }