Adding method to geosvc for Field

JugBase/JugBase/IGeoSvc.h

@@ -35,6 +35,8 @@ public:
   virtual dd4hep::Detector* detector() = 0;
   virtual std::shared_ptr<const dd4hep::rec::CellIDPositionConverter> cellIDPositionConverter() const = 0;
   virtual std::shared_ptr<const Acts::TrackingGeometry> trackingGeometry() const = 0;
+
+  virtual double centralMagneticField() const = 0;
   // receive Geant4 Geometry
   //virtual G4VUserDetectorConstruction* getGeant4Geo() = 0;
 

JugBase/src/components/GeoSvc.h

@@ -57,6 +57,13 @@ public:
    */
   virtual std::shared_ptr<const Acts::TrackingGeometry> trackingGeometry() const;
 
+  virtual double centralMagneticField() const  {
+    return m_dd4hepgeo->field().magneticField({0,0,0}).z();                                                                                  
+  }
+ 
+;
+
+
 private:
 
   /// ACTS Tracking  Geometry

JugReco/src/components/TrackFindingAlgorithm.cpp

@@ -72,7 +72,7 @@ namespace Jug::Reco {
               << "Make sure you have GeoSvc and SimSvc in the right order in the configuration." << endmsg;
       return StatusCode::FAILURE;
     }
-    m_BField                = std::make_shared<Acts::ConstantBField>(Acts::Vector3D{0.0, 0.0, 1.0_T});
+    m_BField                = std::make_shared<Acts::ConstantBField>(Acts::Vector3D{0.0, 0.0, m_geoSvc->centralMagneticField()});
     m_fieldctx              = BFieldVariant(m_BField);
     m_sourcelinkSelectorCfg = {
         {Acts::GeometryIdentifier(), {15, 10}},