// DFCALPhoton member functions

#include "DFCALPhoton.h"

DFCALPhoton::DFCALPhoton()
{
   fEnergy = 0;
   fMom3.SetY(0) ;
   fMom3.SetX(0) ;
   fMom3.SetZ(0) ;
   fMom4.SetXYZT(0.,0.,0.,0.);
}

DFCALPhoton::~DFCALPhoton()
{
}

//
// Tweak shower-depth parameters taken from original Radphi 
// photon-patch to match photon polar-angle in a current GlueX
// environment:
//   30 MeV threshold for deposited energy per FCAL-block after
//   attenuation corrections - MK
//
//#define	FCAL_RADIATION_LENGTH  3.1
//#define	FCAL_CRITICAL_ENERGY  0.01455
//#define	FCAL_SHOWER_OFFSET   3.0 
#define	FCAL_RADIATION_LENGTH  2.9
#define	FCAL_CRITICAL_ENERGY  0.03
#define	FCAL_SHOWER_OFFSET   1. 

// These change with the FCAL attenuation length (L=166cm)
#define	EGAMMA_NORM 0.627419
#define	EGAMMA_EPSILON   0.05259
 
// Simple non-linear correction
void DFCALPhoton::fixEnergy(const double energy) 
{

	double const A=1/EGAMMA_NORM; 				// Normalization factor 
        double const power = 1/(1+EGAMMA_EPSILON); 	        // Non-linear factor
        fEnergy = pow(A*energy,power);

}

// Simple depth correction: estimate shower depth based on shower maximum
// 			    parameters imported from Radphi, but than tweaked 
//			    to match poton polar angle. 
void DFCALPhoton::fixDepth(const double energy, const DVector3 pos) {

// shower position at the face of the FCAL wall
        double r0 = sqrt( pos.X()*pos.X() + pos.Y()*pos.Y() );
	double z0 = FCAL_Zmin - Shower_Vertex_Z;

        double zMax = (FCAL_RADIATION_LENGTH*( 
			FCAL_SHOWER_OFFSET + log(energy/FCAL_CRITICAL_ENERGY)));

// first (zero) approximation takes only shower depth into account
	double z1 = z0 + zMax;
        double t1 = r0/z1; // reconstructed angle = atan(t1)

// do only first angular-dependent depth correction: 
//	there is no need to itterate until z(n)-z(n-1) converge in GlueX 
//      setup since the subsequent angular corrections are much smaller 
//      than the angular resolution
        double z2 = z0 + zMax*( 1 / sqrt( 1 + t1*t1 ) );

        fPosition.SetXYZ(pos.X(), pos.Y(), z2);

}

// Set photon momentum:
// make sure that energy and shower depth are already taken care off.
void DFCALPhoton::setMom3(const double energy, const DVector3 pos) 
{

	double x = pos.X();
	double y = pos.Y();
	double z = pos.Z();

// normalization factor to momenta [GeV]
        double f = energy/sqrt(pow(x,2)+pow(y,2)+pow(z,2)); 
        fMom3.SetXYZ(x*f, y*f, z*f);
}

// Set photon four momentum
void DFCALPhoton::setMom4()
{
   fMom4.SetT(fEnergy);
   fMom4.SetVect(fMom3);
}