center the atof at z=0 (#579)

Author: N-Plx

common-tools/clas-geometry/src/main/java/org/jlab/geom/detector/alert/ATOF/AlertTOFFactory.java

@@ -95,8 +95,9 @@ public AlertTOFLayer createLayer(ConstantProvider cp, int sectorId, int superlay
 		double pad_b1 = 8.17369; // mm
 		double pad_b2 = 10.27; // mm
 
-		double pad_z = 279.7; // mm
-		if (superlayerId == 1) pad_z = 27.7; // mm
+		double atof_length = 279.7; // mm
+		double pad_z = atof_length; // For the bar
+		if (superlayerId == 1) pad_z = 27.7; // mm, for the wedges 10*27.7 + 9*0.3
 
 		// trapezoide dimensions for a smaller paddle (internal)
 		double small_pad_b1 = 7.85924; // mm
@@ -134,8 +135,8 @@ public AlertTOFLayer createLayer(ConstantProvider cp, int sectorId, int superlay
 		for (int padId = 0; padId < current_ncomponents; padId++) {
 
                     //Component index increases with increasing z
-                    double len_b   = padId * pad_z + padId * gap_pad_z; // back paddle plan
-                    double len_f   = len_b + pad_z; // front paddle plan
+                    double len_b   = padId * pad_z + padId * gap_pad_z - atof_length/2; // back paddle plan, centered at z = 0
+                    double len_f   = len_b + pad_z - atof_length/2; // front paddle plan, centered at z = 0
 
                     Point3D p0 = new Point3D(-dR / 2, -widthBl / 2, len_f);
                     Point3D p1 = new Point3D(dR / 2, -widthTl / 2, len_f);