diff -N HelixParamCalculator.java
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ HelixParamCalculator.java	6 Aug 2008 22:21:56 -0000	1.1
@@ -0,0 +1,205 @@

+/*
+ * HelixParameterCalculator.java
+ *
+ * Created on July 7th, 2008, 11:09 AM
+ *
+ * 
+ */
+package org.lcsim.contrib.seedtracker.analysis;
+
+import hep.physics.vec.BasicHep3Vector;
+import org.lcsim.event.MCParticle;
+import org.lcsim.event.EventHeader;
+
+/**
+ * Class used for calculating MC particle track paramters
+ * @author Pelham Keahey
+ * 
+ */
+public class HelixParamCalculator  {
+
+    MCParticle mcp;
+    private double R,BField,theta,arclength;
+    //Some varibles are usesd in other calculations, thus they are global
+    /*
+    xc, yc --coordinates
+    mcdca -- MC distance of closest approach 
+    mcphi0 --azimuthal angle
+    tanL -- Slope SZ plane ds/dz
+    x0,y0 are the position of the particle at the dca
+    */
+    private double xc,yc,mcdca,mcphi0,tanL;
+    private double x0,y0;
+    /**
+     * Constructor that is fed a magnetic field and MCPARTICLE
+     * @param mcpc
+     * @param cBField
+     */
+    public HelixParamCalculator(MCParticle mcpc,double cBField)
+    {
+        //mc and event global varibles used for calculation
+        mcp=mcpc;
+        
+        //Returns the MagneticField at point (0,0,0), assumes constant magfield
+        BField = cBField;
+        
+        //Calculate theta, the of the helix projected into an SZ plane, from the z axis
+        double px = mcp.getPX();
+        double py = mcp.getPY();
+        double pz = mcp.getPZ();
+        double pt = Math.sqrt(px*px + py*py);
+        double p = Math.sqrt(pt*pt + pz*pz);
+        double cth = pz / p;
+        theta = Math.acos(cth);
+       
+        //Calculate Radius of the Helix
+        R = ((mcp.getCharge())*(mcp.getMomentum().magnitude()*Math.sin(theta))/(.0003*BField));
+        
+        //Slope in the Dz/Ds sense, tanL Calculation
+        tanL = mcp.getPZ()/(Math.sqrt(mcp.getPX()*mcp.getPX()+mcp.getPY()*mcp.getPY()));
+       
+        //Distance of closest approach Calculation
+        xc   = mcp.getOriginX() + R * Math.sin(Math.atan2(mcp.getPY(),mcp.getPX()));
+        yc   = mcp.getOriginY() - R * Math.cos(Math.atan2(mcp.getPY(),mcp.getPX()));
+        double xcyc = Math.sqrt(xc*xc + yc*yc);
+            if(mcp.getCharge()>0)
+            {
+            mcdca = R - xcyc;
+            }
+            else
+            {
+            mcdca = R + xcyc;      
+            }
+        
+        
+        //azimuthal calculation of the momentum at the DCA, phi0, Calculation
+        mcphi0 = Math.atan2(xc/(R-mcdca), -yc/(R-mcdca));
+            if(mcphi0<0)
+            {
+                mcphi0 += 2*Math.PI;
+            }
+        //z0 Calculation, z position of the particle at dca
+        x0 = -mcdca*Math.sin(mcphi0);
+        y0 = mcdca*Math.sin(mcphi0);
+        arclength  = (((mcp.getOriginX()-x0)*Math.cos(mcphi0))+((mcp.getOriginY()-y0)*Math.sin(mcphi0)));
+    
+    }
+    /**
+     * Calculates the B-Field from event
+     * @param mcpc
+     * @param eventc
+     */
+    public HelixParamCalculator(MCParticle mcpc,EventHeader eventc)
+    {
+        this(mcpc,eventc.getDetector().getFieldMap().getField(new BasicHep3Vector(0.,0.,0.)).z());
+    }
+    /**
+     * Return the magneticfield at point 0,0,0
+     * @return double BField
+     */
+    public double getMagField()
+    {
+        return BField;
+    }
+    /**
+     * Return the radius of the Helix track
+     * @return double R
+     */
+    public double getRadius()
+    {
+        return R;
+    }
+    /**
+     * Return the theta angle for the projection of the helix in the SZ plane 
+     * from the  z axis
+     * @return double theta
+     */
+    public double getTheta()
+    {
+        return theta;
+    }
+    /**
+     * Return the particle's momentum
+     * @return double mcp momentum
+     */
+    public double getMCMomentum()
+    {
+        return mcp.getMomentum().magnitude();
+    }
+    /**
+     * Return the curvature (omega)
+     * @return double omega
+     */
+    public double getMCOmega()
+    {     
+        return mcp.getCharge()/((mcp.getMomentum().magnitude()*Math.sin(theta))/(.0003*BField));
+    }
+    /**
+     * Return the transvers momentum of the MC particle, Pt
+     * @return double Pt
+     */
+    public double getMCTransverseMomentum()
+    {
+        return (mcp.getMomentum().magnitude())*Math.sin(theta);
+    }
+    /**
+     * Return the slope of the helix in the SZ plane, tan(lambda)
+     * @return double tanL
+     */
+    public double getSlopeSZPlane()
+    {
+        return tanL;
+    }
+    /**
+     * Return the distance of closest approach
+     * @return double mcdca
+     */
+    public double getDCA()
+    {
+      return mcdca;
+    }
+    /**
+     * Return the azimuthal angle of the momentum when at the position of closest approach
+     * @return double mcphi0
+     */
+    public double getPhi0()
+    {
+      return mcphi0;
+    }
+    /**
+     * Return the z position at the distance of closest approach
+     * @return double z0 position
+     */
+    public double getZ0()
+    {
+        double x0 = -mcdca*Math.sin(mcphi0);
+        double y0 = mcdca*Math.sin(mcphi0);
+        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 from the ORIGIN TO THE DCA
+     * @return double arclength
+     */
+    public double getArcLength()
+    {
+        return arclength;
+    }
+    /**
+     * Return the x position of the particle when at the dca
+     * @return double arclength
+     */
+    public double getX0()
+    {
+        return x0;
+    }
+    /**
+     * Return the y position of the particle at the dca
+     * @return double arclength
+     */
+    public double getY0()
+    {
+        return y0;
+    }
+    
+}