PlaneShowerFront.h

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#ifndef _MdGeometryFitterAG_PlaneShowerFront_h_
#define _MdGeometryFitterAG_PlaneShowerFront_h_

#include <TVector3.h>

#include <utl/PhysicalConstants.h>

// Model of the shower front as plane travelling at the speed of light 
// The arrival time of the front at the core postion is a parameter of the model 
// adjusted during the geometrical reconstruction along with the shower axis.       

namespace MdGeometryFitterAG {

  class PlaneShowerFront {

    public:
      PlaneShowerFront(TVector3 axis1, double t01, TVector3 core1) : axis(axis1), t0(t01), core(core1) {}

      // Calculate the arrival time of the shower front at a given position
      double operator()(const TVector3 &pos) const {

        const TVector3 detectorToCore = pos-core;   // desired position wrt the core
        const double detectorHeigth = -axis.Dot(detectorToCore); // height of the detector wrt the shower plane (positive/negative for late/early detectors)
        const double delay = detectorHeigth / utl::kSpeedOfLight; // arrival time of the front at position wrt to the core
        const double arrivalTime = t0 + delay;  // correct the arrival time with the core time
        
        return arrivalTime;
      }

    private:
      TVector3 axis;  // shower axis
      double t0;     // arrival time of the sphere at the core
      TVector3 core;  // core position
  };

}

#endif