diff -u -r1.1 -r1.2
--- WTrack.java	9 Oct 2012 01:20:02 -0000	1.1
+++ WTrack.java	12 Oct 2012 05:54:07 -0000	1.2
@@ -40,14 +40,21 @@

         _parameters = trk.getParameters();
     }
     

-    

     public WTrack(HelicalTrackFit track, double bfield) {

-        _bfield = bfield;
-        _q = (int) Math.signum(track.R());

+        this.initWithTrack(track, bfield, false);
+    }
+    
+    public WTrack(HelicalTrackFit track, double bfield, boolean flip) {
+        this.initWithTrack(track, bfield, flip);
+    }
+   public void initWithTrack(HelicalTrackFit track, double bfield, boolean flip) {
+       double signR = flip ? -1*Math.signum(track.R()): Math.signum(track.R());
+       _bfield = bfield;
+        _q = (int) signR;

         _bfield_constant = Constants.fieldConversion*_bfield*_q;
         
         double a = _bfield_constant;

-        double c = 1/(2*track.R()); //note the different definition than in canonical track

+        double c = 1/(2*Math.abs(track.R())*signR); //note the different definition than in canonical track

         double phi0 = track.phi0();
         double lambda = track.slope(); // lambda = 1/tan(theta)
         double pt = track.pT(_bfield);

@@ -65,13 +72,15 @@

         _parameters[5] = track.dca()*Math.cos(phi0); //y0
         _parameters[6] = track.z0(); //z0
         

-        double pt_tmp = Math.sqrt(_parameters[0]*_parameters[0] + _parameters[1]*_parameters[1]);

         if(_debug) {

-            System.out.println(this.getClass().getSimpleName() + ": a " + a + " R " + track.R() + " c " + c + " phi0 " + phi0 + " pt " + pt);

+            System.out.println(this.getClass().getSimpleName() + ": WTrack initialized from HelicalTrackFit with params");
+            System.out.println(track.toString());
+            System.out.println(this.getClass().getSimpleName() + ": B-field " + _bfield + " q " + _q + " a " + a);
+            System.out.println(this.getClass().getSimpleName() + ": R " + track.R() + " c " + c + " phi0 " + phi0 + " pt " + pt);
+            double pt_tmp = Math.sqrt(_parameters[0]*_parameters[0] + _parameters[1]*_parameters[1]);

             System.out.println(this.getClass().getSimpleName() + ": P0x " + _parameters[0] + " P0y " + _parameters[1] + " -> pt " + pt_tmp);
         }

-    }
-    

+   }

    public void setTrackParameters(double [] params) {
         _parameters = params;
     }