lcsim/src/org/lcsim/fit/helicaltrack

diff -u -r1.7 -r1.8
--- HitUtils.java	20 Feb 2009 22:45:10 -0000	1.7
+++ HitUtils.java	1 Apr 2009 20:50:15 -0000	1.8
@@ -1,3 +1,4 @@

+

 /*
  * HitUtils.java
  *

@@ -179,9 +180,13 @@

         //  Calculate the uncertainty in the unmeasured coordinate due to not knowing the track direction
         //  by assuming phat . u has an uncertainty of 2/sqrt(12) so dv = 2 / sqrt(12) * seperation / sin(alpha)
         double dv = Math.abs(2. * separation / (Math.sqrt(12) * salpha));

-        //  Add the covariance contributions from not knowing the track direction cov += (v1 * v1^T + v2 * v2^T) * (dv/2)^2
-        MatrixAdd(Vec2Matrix(VecOp.mult(dv * factor, strip1.v())), cov);
-        MatrixAdd(Vec2Matrix(VecOp.mult(dv * factor, strip2.v())), cov);

+        //  Don't let dv by greater than the strip length / sqrt(12)
+        double dv1 = Math.min(dv, (strip1.vmax()-strip1.vmin()) / Math.sqrt(12.));
+        double dv2 = Math.min(dv, (strip1.vmax()-strip1.vmin()) / Math.sqrt(12.));
+        //  Add the covariance contributions from not knowing the track direction
+        //  cov += v1 * v1^T * (dv1/2)^2 + v2 * v2^T * (dv2/2)^2
+        MatrixAdd(Vec2Matrix(VecOp.mult(0.5 * dv1, strip1.v())), cov);
+        MatrixAdd(Vec2Matrix(VecOp.mult(0.5 * dv2, strip2.v())), cov);

         return new SymmetricMatrix(cov);
     }