Expose UT sector dxDy for Allen.

Det/UTDet/include/UTDet/DeUTSector.h

@@ -556,6 +556,9 @@ public:
   /** getter for dy */
   [[nodiscard]] double get_dy() const { return m_dy; }
 
+  /** getter for dxdy */
+  [[nodiscard]] double get_dxdy() const { return m_dxdy; }
+
   /// get half length in x an y
   std::pair<double, double> halfLengths() const;