lcsim/src/org/lcsim/fit/helicaltrack

diff -u -r1.1 -r1.2
--- HelixParamCalculator.java	7 Jul 2008 18:44:21 -0000	1.1
+++ HelixParamCalculator.java	7 Jul 2008 23:03:55 -0000	1.2
@@ -27,8 +27,9 @@

     mcdca -- MC distance of closest approach 
     mcphi0 --azimuthal angle
     tanL -- Slope SZ plane ds/dz

+    arclength --arclength of he helix 

     */

-    private double xc,yc,mcdca,mcphi0,tanL;

+    private double xc,yc,mcdca,mcphi0,tanL,arclength;

     
     public HelixParamCalculator(MCParticle mcpc,EventHeader eventc)
     {

@@ -74,6 +75,11 @@

             {
                 mcphi0 += 2*Math.PI;
             }

+        //z0 Calculation, z position of the particle at dca
+        double x0 = -mcdca*Math.sin(mcphi0);
+        double y0 = mcdca*Math.sin(mcphi0);
+        arclength  = (((mcp.getOriginX()-x0)*Math.cos(mcphi0))+((mcp.getOriginY()-y0)*Math.sin(mcphi0)));
+    

     }
     /**
      * Return the magneticfield at point 0,0,0

@@ -159,6 +165,14 @@

         double s  = (((mcp.getOriginX()-x0)*Math.cos(mcphi0))+((mcp.getOriginY()-y0)*Math.sin(mcphi0)));
         return mcp.getOriginZ()-(s*tanL);
     }

+    /**
+     * Return the arclength of the helix
+     * @return double arclength
+     */
+    public double getArcLength()
+    {
+        return arclength;
+    }

    
     
 }